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2006 - 2008 Literature Review Archives - Impacts and Adaptation
Aherne, J. et al., (July 15, 2006) Climate variability and forecasting surface water recovery from acidification: Modelling drought-induced sulphate release from wetlands. Science of the Total Environment, 365(1-3)):186-199doi:10.1016/j.scitotenv.2006.02.041.
This paper, whose lead author is at Trent University, details use of the MAGIC groundwater acidification model to estimate the ability of an acidified lake to recover from historical deposition under two different climate scenarios. In one scenario, the total precipitation and catchment runoff over the 1980-2000 period were divided so as to eliminate interannual variability. In the second, the same period's variability was reproduced, including six years in which "drought months" were observed. Both scenarios were run to 2080. In the first (low variability) scenario, projected sulphur emission reductions from Canada's post-2000 Acid Rain Strategy and the U.S.'s proposed Clear Skies Legislation resulted in significantly higher rates of recovery from acidification of a Central Ontario lake than in the present-day variability scenario. The theoretical basis for this result is that drought causes oxidation of stored sulphur (from years of deposition) in wetlands and subsequent export of sulphate to surface waters with precipitation. The authors call for finer-resolution downscaled GCM outputs to more accurately predict likely climate variability impacts. This paper suggests that anthropogenic climate change (including climate variability) may have already been responsible for an exacerbation of Canada's acid deposition problem, and may continue to delay recovery in the future.
Alsos, I.G., Eidesen, P.B., Ehrich, D., Skrede, I., Westergaard, K., Jacobsen, G.H., Landvik, J.Y., Taberlet, P. and Brochmann, C. 2007. Frequent long-distance plant colonization in the changing Arctic. Science Vol 316 June 15, 2007, pp 1601-1608.
A study of native Arctic plants on the Svalbard Archipelago reveals that current plant populations originated from a number of distant locations. The results suggest that long-distance dispersal is not likely to be a limiting factor in the ability of plant species to track changes in their ecological niches in the future.
Climate warming is expected to cause the distribution of many species to shift northward. Questions exist, however, about the ability of species to track changes in their ecological niche. The authors tested the hypothesis that dispersal ability may limit shifts in species' ranges by studying the colonization history of nine plant species known to have become established on Svalbard, a remote Arctic archipelago, after the last glacial retreat. They analyzed the genetic variation of 4439 samples from most of the geographic ranges of the nine species and used DNA fingerprinting techniques to show that colonization of Svalbard has occurred repeatedly from several source regions. They conclude that assuming unlimited dispersal when predicting long term range shifts in the Arctic may be appropriate. The study further showed that the 'genetic bottleneck' of colonization - where new populations are established by a limited number of founding members with limited genetic variability (and hence adaptation potential) - is, however, likely to be a limiting factor in successful establishment.
Amstrup, S.C., I. Stirling, T.S. Smith, C. Perham and G.W. Thiemann. Recent observations of intraspecific predation and cannibalism among polar bears in the southern Beaufort Sea. Polar Biology (2006) DOI:10.1007/s00300-006-0142-5.
The authors report three incidents of killing and consumption of polar bears in winter 2004 by other polar bears in the Beaufort Sea. Ecological factors motivating intraspecific predation in bears are enumerated. During their combined years of polar bear research the authors have not seen other evidence of such predation behavior and hypothesize that these events may be related to nutritional stress brought about by longer ice-free seasons in the region. In the first case, where a female bear was killed in a maternal den, the site was at least 25 km from typical habitat of males and the evidence suggested that the male was specifically searching for occupied dens. In the other cases of predation on sea ice, tracks indicated that the victims were actively hunted down and killed. The underlying causes of this unusual phenomenon remain unknown and point to the need for continuing long term studies of ecosystems in relation to ongoing and predicted sea ice changes.
Battisti, D.S. and Nalyor, R.L. 2009. Historical warnings of future food security with unprecedented seasonal heat. Science 323:240-244; Wisser, D., Frolking, S., Douglas, E.M. et al., 2008. Global irrigation water demand: variability and uncertainty arising from agricultural and climate data sets. Geoph. Res. Lett. 35, L24408, doi:10.1029/2008GL035296,2008.
Two recent papers explore the human consequences of future climate change through decreased food security. They conclude that high heat increases the stress on crops and livestock, particularly in low latitudes, and hence may generate a food security crisis that will be difficult to address through adaptive measures.
In the first paper, American scientists Battisti and Naylor present their analysis of global growing season temperature projections generated by 23 different climate models. The results suggest a greater than 90% probability that, by the end of the 21st century, average growing season temperatures in the tropics and subtropics will exceed the most extreme seasonal temperatures observed there during the past century. In temperate latitudes, where growing season temperatures vary more, the hottest seasons now observed will become the average in the future. Historical examples indicate that, currently, hot seasons significantly increase stress on crops and livestock, particularly in low latitudes where about half of the world's population now lives. Given that global food movement from surplus to shortage areas and the use of adaptive strategies to cope with weather related challenges in food production is already a major challenge today, the human consequences of the projected changes in food security could be enormous. The second paper, written by a team of American and German researchers, looks more specifically at the use of crop irrigation as an adaptive measure. Currently, about 70% of total global use of surface and groundwater is for crop irrigation. Their study, using hydrological models, suggests that past changes in weather conditions have caused this demand to vary by 10% on a global scale, and by as much as 70% at the national scale. Since years with high water demand for irrigation are also usually years with low water supply, effective management of water supply for drought relief becomes a daunting challenge.
Bell, M., Goldberg, R., Hogrefe, C., et al., 2007. Climate change, ambient ozone, and health in 50 US cities. Climatic Change 82: 61-76.
More evidence that future climate change will lead to an increase in summertime ozone levels and related health impacts. A study of 50 eastern US cities predicted an increase in summertime ozone levels by 2050 relative to 1990 leading to a significant rise in the daily total mortality rate within the metropolitan areas studied.
An American study recently published in the journal Climatic Change used a climate/air quality modeling system to project changes in future ground-level ozone in 50 eastern U.S. cities. The study isolated the response of tropospheric ozone concentrations to climate change, while disregarding changes in anthropogenic emissions. Hourly ambient ozone concentration levels from the summers of 1993-1997 were compared to those projected for 2053-2057 summers based on the IPCC A2 scenario. The study also looked at changes in "exceedance days" relative to regulatory standards. The model projected daily average maximum ozone level increases of 4.8 and 4.4 ppb (1- and 8-h maximum) between 1990 and 2050, with the largest increases expected for cities already experiencing elevated ozone levels. The number of exceedance days increased for both the 1- and 8h studies, by an average of 0.6 and 5.5 days respectively, while the Air Quality Index (AQI) scale showed a 10% increase in the number of days with "adverse health effects" and an 8% increase in days with 'unhealthy conditions'. Based on concentration/response functions, the simulated changes in ground-level ozone concentrations correspond to an approximate increase of 0.11% to 0.27% in daily total mortality.
Cao, L. and K. Caldeira. 2008. Atmospheric CO2 stabilization and ocean acidification. GRL Vol 35, L19609, doi:10.1029/2008GL035072, 2008. 5 pp.
Ocean chemistry will be significantly perturbed even if atmospheric CO2 concentrations are stabilized at low to moderate levels. Protection of marine ecosystems could require a CO2 stabilization level that is lower than what might be chosen on the basis of climate considerations.
Cao and Caldeira investigate the consequences for ocean chemistry of stabilizing atmospheric CO2 at various levels, ranging from 280 ppm (pre-industrial levels) up to 2000 ppm. They ask three questions: 1) how the calcium carbonate saturation state of seawater surrounding existing coral reefs will change under the various stabilization scenarios, 2) what CO2 stabilization levels are required to avoid undersaturation of different parts of the ocean for either aragonite or calcite (the two major forms of calcium carbonate used by calcifying organisms), and 3) how ocean pH will change. They use the University of Victoria's Earth System Climate Model (version 2.8), a model of intermediate complexity, with simulations extending out to year 2500. The stabilization year varies with stabilization level, and is 2010 for the 380 ppm pathway, 2100 for the 450 ppm pathway, with increases of 25 years for each 50 ppm increase thereafter. They find that at pre-industrial conditions, over 98% of coral reefs were found near open water supersaturated with aragonite (with a saturation state of >3.5). This declines to 8% of coral reefs at an atmospheric stabilization level of 450 ppm CO2. Corals require water that is highly supersaturated with aragonite to be able to build reefs efficiently. Declines in aragonite saturation state have the potential to weaken the calcification ability of coral reefs and may lead to long term instability of reef structures. The results also showed that at stabilization levels as low as 450 ppm CO2, parts of the Southern Ocean become undersaturated (7% of the ocean south of 60°S). At 550 ppm CO2, half of the ocean south of 60°S becomes undersaturated. (High latitude oceans are expected to become undersaturated first since their natural saturation state for calcium carbonate is lower than that of ocean water at lower latitudes.) Finally, stabilization at 450 ppm CO2 results in a decline in ocean pH of >0.2 units in more than 10% of the surface ocean, violating criteria for protecting marine ecosystems already established by some environmental protection agencies. At 550 ppm, most of the surface ocean experiences a pH decrease of >0.2 units. The authors conclude that preservation of marine ecosystems may require that atmospheric CO2 be stabilized at lower levels than what might be required on the basis of climate considerations.
Cao, L., K. Cladeira, and A.K. Jain. 2007. Effects of carbon dioxide and climate change on ocean acidification and carbonate mineral saturation. GRL Vol 34,L05607, doi:10.1029/2006GL028605. Also, McNeil, B.I. and R.J. Matear. 2007. Climate change feedbacks on future oceanic acidification. Tellus 59B, 191-198.
Two papers on the subject of climate change and ocean acidification published recently conclude that future reductions in ocean acidification will be driven primarily by changes in atmospheric CO2 levels, rather than by climate change feedbacks.
A number of modeling studies have investigated the impact of future atmospheric CO2 changes on ocean chemistry. These predict declines in ocean pH and a lowering of the calcium carbonate saturation state of seawater. Two recent papers ask whether climate change (for example, through increased SSTs) will have additional impacts on ocean chemistry. A paper by Cao et al, published in GRL, used an earth system model of intermediate complexity to simulate future climate change with CO2 emissions derived from a 1000 ppm CO2 stabilization scenario and with climate sensitivity set at three different levels: 0.0°C (i.e. no climate change), 2.5°C and 4.5°C. With constant climate, ocean pH is reduced by 0.47 units, while it is reduced by 0.48 and 0.51 in the other two scenarios. This demonstrates that consideration of climate change introduces additional reductions in ocean pH but that these are small relative to the direct effect of increased atmospheric CO2. Similar conclusions were drawn with regard to the impacts on ocean calcium carbonate saturation state, an important environmental variable for marine organisms such as corals. McNeil and Matear, in a paper published in Tellus, examine the sensitivity of ocean pH and aragonite (a form of calcium carbonate) to climate change feedbacks within a coupled ocean-atmosphere model. The authors also found that future ocean surface pH is independent of the amount of ocean warming, implying that future projections of surface ocean acidification need only consider future atmospheric CO2 levels, not climate change induced modifications in the ocean.
Cheng, C.S., H. Auld, G. Li, J. Klassen and Q. Li, 2007. Possible impacts of climate change on freezing rain in south-central Canada using downscaled future climate scenarios. Nat. Hazards Earth Syst., 7: 71-87.
By the 2050s, south-central Canada could see a significant increase in freezing rain events from December to February and by the 2080s, the increase could be even greater.
Three Environment Canada researchers have published the results of a study investigating the impacts of a warming climate on the occurrence of freezing rain events for the south-central region of Canada (northern, eastern and southern Ontario, plus southern Quebec). Using recognized methodologies, the study first considered daily and hourly historical relationships between weather types and freezing rain events (November to April for the period 1958/59 to 200/01), then used statistically downscaled future climate scenarios from four global climate models (GCMs) under three different emissions scenarios (A2, B2 and IS92a), to assess the possible changes in future freezing rain events for the 2050s and the 2080s. The results showed projected increases in the number of events for all sub-regions during the colder months (December to February), especially in northern Ontario. During the warmer months (November, March and April) small increases in freezing rain events are projected for northern Ontario, decreases are projected for southern Ontario, while no changes are projected for Eastern Ontario and southern Quebec. Where increases in events are projected, the increases are larger in the 2080s than in the 2050s (e.g. a 135% vs 85% increase in events in northern Ontario during the colder months). The results of this study are intended to provide provincial and municipal decision makers with scientific information needed in emergency planning and adaptive capacity improvement.
Cherry, S.G., Derocher, A.E., Stirling, I. and Evan, S.R. 2009. Fasting physiology of polar bears in relation to environmental change and breeding behavior in the Beaufort Sea. Polar Biology DIO10.1007/s00300-008-0530-0.
Polar bear fasting physiology shows promise as an early warning monitoring tool to assess changes in feeding ecology related to environmental stressors such as climate change.
Polar bears are dependent on the reliability of the sea ice platform to hunt seals, their main prey species. Given the recent declines in Arctic sea ice there is interest in investigating what impacts changing sea ice conditions might have on polar bear populations. A recent study, by a team of researchers that includes two Environment Canada scientists, uses values of a physiological biomarker (serum urea to creatinine ratios) to test the hypothesis that polar bear feeding successes differed in response to climate-induced changes in sea ice conditions. In the study, blood samples were collected from two Beaufort Sea polar bear populations in 1985 and 1986, and again in 2005 and 2006 to assess nutritional stress. The study also investigated the relationship between fasting frequency and body mass and looked for broad-scale geographic differences between the two populations. The authors observed that polar bears of all ages, sex and reproductive status in 2005 and 2006 were more likely to be in a physiological fasting state than in the 1980s. This is consistent with reports regarding changes in a range of factors including prey availability, breeding behavior, cub recruitment, and ice and meteorological conditions though the precise cause of the change in fasting status remain unknown. Over time the study found no relationship between the incidence of physiological fasting and body mass since body mass was also low in the 1980s. This may be related to the lowered abundance of ringed seals in the mid 1980s independent of sea ice conditions. The authors recommend the incorporation of serum measurements into long term monitoring programs of polar bears as a way of providing early indications of nutritional stress not otherwise detectable.
Cleland, E.E., Chiarello, N.R., Loarie, S.R., Mooney, H.A. and Field, C.B. 2006.
Diverse responses of phenology to global changes in a grassland ecosystem. Proceedings of the National Academy of Sciences (PNAS) 103:37:13740-13744. There is abundant evidence now in the scientific literature about shifting phenology in both plant and animal species in response to climate warming, but the pattern is not universal, and while accelerated phenology is the dominant response to date, some examples of delayed phenology have been reported. This paper serves to remind that phenological changes are likely to reflect not only changing temperatures but also changes in other environmental conditions. The authors used experimental grassland plots (in California) to expose plants to a range of altered environmental conditions, including warming (+1.5 C), elevated CO2 (680 ppm), enhanced nitrogen deposition (7gN/m2/yr) and increased precipitation (+50% for each rainfall event and an extended wet season). While warming accelerated the onset of flowering in all annual species, both elevated CO2and experimental N deposition caused accelerated flowering in forbs but delayed flowering in grasses. In the latter case, the combination of elevated CO2and warming produced an offsetting response, such that first flowering dates were no different than in controls. Increased precipitation had no effect on first flowering dates in either grasses or forbs, a finding in agreement with previous work.
Cook, K.H. and E.K. Vizy. 2008. Effects of twenty-first century climate change on the Amazon rain forest. J. Climate Vol 21 pp 542-560.
A 70% reduction in the extent of the Amazon Rain Forest by the end of the 21st century is projected by a regional climate model driven by the Canadian Global Climate Model. The projection is based on the IPCC A2 emission scenario, which assumes continued growth in GHG emissions at about present day rates.
The future of the Amazon rain forest in a warming world is a concern for many reasons, one of which is the potential for positive feedbacks to global climate if the forest were to decline substantially. This paper by Cook and Vizy uses a regional climate model (MM5 v.3.6 from Penn State University/NCAR) coupled to a potential (equilibrium) vegetation model to investigate the implications of twenty-first century climate change for tropical and subtropical South America, focusing on the Amazon rain forest. Output for 2081-2100 from the Canadian Global Climate Model (CGCM3.1) forced by the IPCC A2 emission scenario was used to provide the boundary conditions for the regional climate model (RCM) simulation. The RCM was coupled to the vegetation model through an iterative process whereby the initial RCM simulation uses prescribed vegetation but then subsequent runs use the new vegetation distribution resulting from the previous iteration. The process continues until the vegetation distribution stabilizes. Projected changes in vegetation under such an approach assume that climate change is slow enough that the vegetation remains in equilibrium with the climate. The coupled regional model simulation projects a 70% reduction in the extent of the Amazon rain forest by the end of the twenty-first century (2081-2100). Rain forest vegetation disappears entirely from Bolivia, Paraguay and Argentina and most of Brazil and Peru. All of the surviving rain forest is concentrated close to the equator. The decline of the rain forest is due to a reduction in annual mean rainfall and a lengthening of the dry season over much of tropical and subtropical South America.
De Wit, M and J. Stankiewicz. 2006. Changes in Surface Water Supply across Africa with Predicted Climate Change. Science, March 31, 2006 vol 311. 10.1126/science.1119929.
Drainage has been shown in previous studies to have a non-linear relationship with precipitation across Africa, with different regimes distinguished by different threshold amounts of precipitation. In some areas, a small decrease in precipitation would greatly impact surface drainage. This study makes use of the Africa Earth Observatory network's African database and develops a model to predict the perennial water supply across Africa by the end of the century. In regions receiving 1000 mm per year of rainfall, a 10% decrease in precipitation would reduce drainage by 17% whereas regions receiving 500 mm per year would see a drop by 50% of the surface drainage. By using predicted precipitation changes from results of the Climate Change Assessment Project for Africa the authors calculate that a decrease in perennial drainage will significantly affect present surface water access across 25% of Africa by the end of this century. Such a situation would put tremendous stress on populations and water scarcity could become a source of international conflict.
Donaldson, G.C. 2006. Climate change and the end of the respiratory syncytial virus season. Clinical Infectious Diseases 42:677-679.
Analysis of about two decades of hospital admissions (1990-2004) and hospital lab reports (1981-2004) across England and Wales suggest that the season for the RSV virus (which is a prime cause of bronchiolitis and pneumonia amongst small children, but can affect all age groups) has been ending about 2 to 3 weeks earlier for each degree of rise in regional annual air temperatures. In contrast, rising temperatures have not affected the onset of the season.
Elsner, James B. 2006. Evidence in support of the climate change - Atlantic hurricane hypothesis. Geophysical Research Letters 33. DOI: 10.1029/2006GL026869.
A number of recent articles have been published dealing with the putative causal link between climate change and tropical cyclone activity. Another such paper appeared recently, the results of which support a causal link. The author, a geographer at Florida State University, used statistical methods to evaluate the Granger causality of the association between global mean near-surface temperature (GT) and Atlantic sea-surface temperature (SST), and of the association between Atlantic SST and the average intensity of tropical cyclones. For both associations, the period in question covered 1851-2005. One quantity is said to be Granger causal for another when the first quantity can be used to predict the second, but not vice versa. Thus the author evaluated whether GT can be used to predict Atlantic SST, and whether Atlantic SST can be used to predict hurricane intensity, as measured by the power dissipation index (PDI). He found that time-lagged GT could be used to predict Atlantic SST and not vice-versa; similarly, time-lagged Atlantic SST could be used to predict Atlantic PDI and not vice versa. The findings are consistent with the hypothetical causal link from climate change (and therefore GT) through Atlantic SST to increased hurricane intensity.
Fleury, M., Charron, D.F., Holt, J.D., Allen, O.B. and Maarouf, A.R. 2006. A time series analysis of the relationship of ambient temperature and common bacterial enteric infections in two Canadian provinces. Journal of Biometeorology, Online article DOI: 10.1007/s00484-006-0028-9.
A recent study by Guelph University students investigated the relationship between short-term variations in ambient temperature and the weekly occurrence of the three most commonly reported bacterial enteric infections in Canada: Campylobacter, Salmonella and Escherichia coli. The 9-year study (1992-2000) used minimum, maximum and average weekly temperatures from 92 Alberta and 59 Newfoundland-Labrador stations operated by Environment Canada, with a 0 to 6 week lag period applied to the mean values as a result of the delayed effect of temperatures on foodborne illness. Results showed that although no increased risk of infection was observed for temperatures below -10° to 0°C (with the threshold temperature varying with the type of pathogen), the relative risk of foodborne illness did increase with warmer temperatures. In Alberta, a significant non-linear relationship was observed between temperatures and all three types of pathogens, while in Newfoundland-Labrador, the increase was only observed for Campylobacter. The study supports results obtained in other studies conducted in Australia and Europe.
Ford, J.D., B. Smit and J. Wandel. Vulnerability to climate change in the Arctic: A case study from Arctic Bay, Canada. Global Env. Change. Vol 16, Issue 2, May 2006, Pages 145-160.
In 2005, the ACIA provided evidence that climate change is already occurring at higher latitudes and identified assessing vulnerabilities as a major area for further research. This paper reports on the first component of a comprehensive vulnerability assessment in the Canadian Arctic. Results from climate modelling in the Arctic suggest that the region around the community of Arctic Bay, on Baffin Island, could experience a decrease in maximum ice thickness of 0.5m and a decrease in duration of ice conditions by 2 months towards the end of the century. There are uncertainties regarding future abundance, distribution and access to species important to the local Inuit diet (seals, caribou and narwal). In this study, a conceptual model is used in which exposure sensitivity and adaptive capacity are the central interdependent elements. The Arctic Bay case study was based on a semi-structured interview process of 65 residents regarding their ability to deal with risk. Findings indicate that adaptability is facilitated by traditional Inuit knowledge, strong social networks, flexibility in seasonal hunting cycles, modern technologies, and economic means. Adaptive capacity is undermined by changing livelihoods, the breakdown of intergenerational knowledge transfer, and weakened social networks associated with a wage based economy. The ability to cope with changes therefore will vary among different groups in the community and will be affected by social, cultural and economic conditions.
Ford, J., T. Pearce, B. Smit, J. Wandel, M. Akkurut, K. Shappa, H. Ittusujurat and K. Qrunnut. 2007. Reducing Vulnerability to Climate Change in the Arctic: The Case of Nunavut, Canada. Arctic Vol.60, No.2 p150-166.
Research in two Nunavut communities identifies key areas where Inuit can reduce their vulnerability to climate change.
A study of vulnerability to climate change in the Canadian Arctic was published in the most recent issue of the journal Arctic. The authors begin by identifying an adaptation policy deficit with regard to the vulnerability of Arctic communities to the problems posed by climate change. The paper responds by outlining key areas in which policy can reduce vulnerability, specifically with regard to renewable resource harvesting. "Second generation" adaptation policy research recommends the integration or "mainstreaming" of climate change risk considerations into existing decision making processes to avoid community vulnerability. Case studies conducted in the Nunavut communities of Arctic Bay and Igloolik form the basis of the vulnerability assessments. Inuit have developed various adaptive strategies (with associated costs) in response to climate change risks. Policy interventions relating to cultural preservation, wildlife management and harvester support have the potential to reduce the erosion of Inuit Traditional Knowledge and land-based skills of youth, and maintain social networks and harvesting flexibility. Interventions will be more successful if they are developed in cooperation with local people. The policy options recommended in this paper were developed in collaboration with the two communities and reviewed using radio and "town hall" presentations.
Fyfe, J.C. and Saenko, O.A. 2007. Anthropogenic speed-up of oceanic planetary waves. GRL Vol. 34,L10706, doi:10.1029/2007GL029859, 2007.
A new Canadian climate modelling study suggests that human influences may already be affecting the dynamics of the oceans in a manner that increases the frequency of ocean climate events such as El Niños. The authors of the study predict that further increases in the frequency of such events, as the climate warms, will likely have significant impacts on the interannual variability of our climate - and hence of our weather.
A recent paper by Environment Canada climate modellers John Fyfe and Oleg Saenko, looked at the impact of global warming on ocean dynamics using CGCM3 simulations of past and future climate change. Specifically, Fyfe and Saenko looked at the response to human interference of ocean 'waves' (known as oceanic planetary waves) that constantly move from east to west across the world's oceans as a result of the interplay of the Earth's rotation and shape. These very long waves move very slowly. For example, they can take one to two years to transit the Pacific near the equator, and a decade or so to cross the North Pacific. Past studies have shown that these planetary waves significantly affect the movement of the atmosphere and ocean waters, and are strongly linked to oscillations in ocean climate, particularly that of El Niño-Southern Oscillation (ENSO). Model simulations of future climate change under the SRES A2 emission scenario (a high emission scenario) suggest that the speed of movement of these waves across the planet will increase by 35% by 2100. This is likely to cause a significant increase in the frequency of oscillations such as ENSO, and hence make climate more variable.
Gedney, N., P.M. Cox, R.A. Betts, O. Boucher, C. Huntingford and P.A. Stott. 2006. Detection of a direct carbon dioxide effect in continental river runoff records. Nature 439: 835-838.
This study used the well defined methodology of optimal fingerprinting methodology (widely used in climate change attribution and detection studies) to determine the cause of the observed 20th Century increase in continental river runoff. Four possible contributors were examined: climate change; deforestation; solar dimming (reduced solar radiation reaching the atmosphere); and the direct effects of CO2 on plant transpiration. They found that the 20th Century climate alone was unable to explain the observed runoff trends. However, the trends were found to be consistent with a suppression of plant transpiration due to CO2-induced stomatal closure. This study is important as, although laboratory experiments have shown that enhanced CO2 would decrease stomatal openings of many plant species and thus reduce evapotranspiration, it was unclear whether this would be the case in the field. Furthermore, this study is the first to suggest that raised CO2 levels are already having a direct influence on the water balance at the land surface.
Goulet, T.L. 2006. Most corals may not change their symbionts. Marine Ecology Progress Series Vol 321:1-7.
This paper tests the hypothesis that corals may survive climate change by developing new symbiotic relationships with algal types better suited to the changed environment. This 'adaptive bleaching' hypothesis assumes that a coral species can host multiple algal genotypes. A large dataset collected over 15 years (43 studies of 442 coral species) was used to assess the generality of symbiont turnover among coral species. The results show that only 23% of coral species host multiple zooxanthella clades (a clade is a taxonomic grouping of algae). Most coral species (77%) exhibit fidelity to a single clade, and show no evidence of being able to exchange symbionts in response to either a change in geographic location or environmental stress. The implication of this, the author notes, is that if climate warming continues, coral reefs may undergo a reduction in biodiversity with only those species capable of algal switching and those capable of withstanding the change in water temperatures, able to survive.
Gray, D.R., 2008. The relationship between climate and outbreak characteristics of the spruce budworm in eastern Canada. Climatic Change, 87: 361-383.
A large scale study was done to investigate the relationship between climate and spruce budworm outbreaks in eastern Canada. The results show that outbreak characteristics are strongly related to climate and that these outbreaks will likely be longer and more severe by the end of the century, especially in the southern regions of eastern Canada.
The eastern spruce budworm is one of the most damaging insects to forests of North America. A scientist from the Canadian Forest Service has investigated the relationship between spruce budworm outbreak characteristics and the combination of climate, forest composition and spatial location. The study covered a vast region east of the Manitoba-Ontario border and south of 52°N. For the climatic part of the analysis, the historical climate was derived from the 1961-1990 climate normals, and daily weather variables were simulated using a stochastic weather generator. Thirteen climate variables were chosen a priori for analysis which characterized the summer and winter climates that would be expected to influence insect survival, fecundity etc. and disease development. The projected future climate (2081-2100) was provided by daily simulations produced by the third Coupled Global Climate Model of the Canadian Centre for Climate Modelling and Analysis, under the IPCC SRES-B1 experiment. The historical results show that spruce budworm outbreaks lasted on average about 9 years (with a maximum in New-Brunswick of about 14 years and a minimum in Newfoundland of about 6 years), and that outbreaks were more severe in Ontario (about 57% defoliation) and least severe in Newfoundland (about 34% defoliation). Approximately 54% of the spatial variability in outbreak characteristics can be explained by the spatial pattern of the climate, with summer degree-days having the strongest influence. The analysis showed an average increase in outbreak duration of about 6 years by the latter part of the century, over the whole study area, with the largest increases predicted for eastern Quebec and the Gaspé Peninsula. The analysis also showed an overall increase in outbreak severity of 15%, but with very large regional differences.
Hamann, A. and T. Wang. 2006. Potential effects of climate change on ecosystem and tree species distribution in British Columbia. Ecology 87:11: 2773-2786.
Bioclimatic envelope studies use climate data as independent predictor variables and biological data as dependent variables in order to generate predictive models for species or ecosystem distribution. Climate change data can be incorporated into such work as well to generate projections of how species or ecosystems may shift in response to future climate change. Authors Hamann and Wang, of UBC, apply such an approach to investigate the potential effect of climate change on forest communities and tree species in British Columbia. Climate change scenarios were provided by CGCM1 (using IS92a), and by CGCM2 and HADCM3 (using the SRES scenarios A2 and B2). Both baseline and future climate data were downscaled to 400-m resolution. Projections of ecosystem change were based on the Biogeoclimatic Ecological Classification system for B.C., with some modifications applied to better accommodate elevation differences within the Alpine Tundra zone. The authors found that tree species (both hardwoods and conifers) with their northern range limit in B.C. gain potential habitat toward the north at a rate of at least 100 km per decade, and increase in number where they already occur. Hardwoods occurring throughout B.C. appear generally unaffected by climate change. However, some of the most important conifer species are expected to significantly decrease in frequency and/or lose a large portion of their suitable habitat. Considerable spatial redistribution of ecosystems is projected, with currently important sub-boreal and montane climate regions rapidly disappearing.
Hansen, J. et al., (2007), Dangerous human-made interference with climate: a GISS modelE study, Atmos. Chem. Phys., 7, 2287-2312.
A well publicized paper by NASA lead scientist James Hansen, and a suite of co-authors, makes headlines with news that the Earth is approaching a dangerous tipping point. The paper itself is a synthesis of new modeling work combined with an analysis of existing science on the impacts of climate change. The news coverage was a little misleading in that the paper does not present any new science for identifying critical levels of climate change. However, Hansen and co-authors present well reasoned arguments supported by science for limiting global warming to about 1°C above the year 2000.
The objective of the Framework Convention on Climate Change (UNFCCC) is to stabilize greenhouse gas (GHGs) concentrations at a level that would avoid dangerous anthropogenic interference with climate. What would constitute 'dangerous' climate change has been the subject of much debate. In a recent paper, a large team of authors from multiple institutes, led by James Hansen of NASA's Goddard Institute for Space Studies, investigate this issue presenting a "mini-synthesis" of their own and other scientists' work on future projections and impacts of climate change, and emission reduction scenarios to limit global warming. The future climate is simulated by the atmospheric climate model GISS modelE coupled with an ocean model for three IPCC emission scenarios which correspond to the near maximum (A2), minimum (B1) and midrange (A1B) scenarios, and for two alternative scenarios; one that keeps further global warming under 1°C and one that keeps it to about 2°C. The global warming in all the IPCC scenarios exceeds 1°C by 2100. The authors focus their discussion of the impacts of climate change to three specific cases: Arctic climate change, tropical storm intensification and ice sheet and methane hydrate stabilities. They conclude that in all three cases, limiting future warming to 1°C above year 2000 significantly reduces the risks of triggering dangerous anthropogenic climate change. The authors also note, that judging from recent Earth history, if the warming is less than 1°C, strong positive feedbacks are not unleashed but, if global warming gets well out of this range, positive feedbacks could set in motion climate changes far outside the range of recent experience. They conclude that a CO2 level exceeding about 450 ppm is 'dangerous' but that limiting atmospheric CO2 to this level, in combination with decreases in non-CO2 forcings, could together be sufficient to avoid dangerous climate change.
Irons, D.B., T. Anker-Nilssen, A.J. Gaston and many authors. 2008. Fluctuations in circumpolar seabird populations linked to climate oscillations. Global Change Biology, 14:1-9.
Two Arctic seabird species are shown to be more sensitive to the rate of change in sea surface temperature than to whether it is warming or cooling.
Most analyses of the effects of global climate change on ecosystems and species have been local in scale. Larger-scale analyses usually require the coordinated efforts of scientists from many countries. Recently, a number of scientists from countries around the circumpolar Arctic teamed up to evaluate the impact of changes in sea surface temperature (SST) on seabird populations, pooling their data on population trends for two seabirds, the Common and Thick-billed Murres. Between them, these two related species inhabit most of the temperate and polar waters of the northern hemisphere, with the Thick-billed Murre favouring colder water habitat while the Common Murre prefers more temperate waters. The researchers investigated how decadal regime shifts in climate (associated with changes in atmosphere-ocean circulation), as measured by changes in SST, have influenced population change in these two seabird species across their entire circumpolar range. In the 1970s, both the North Pacific and the North Atlantic climatic oscillations shifted from a negative to a positive regime with parallel but opposite shifts in SSTs. The mid-1970s regime shift was the largest recorded in the northern-hemisphere. A later regime shift in 1989 was in comparison relatively small. The researchers were able to demonstrate synchronous fluctuations of the two seabird species linked to the two climate regime shifts. They were also able to demonstrate that the magnitude of the SST shift was more important than its direction in determining the rate of population change. Seabirds declined when the SST shift was large, irrespective of the direction of the SST change, and increased when the shift was small. The authors suggest that murres are sensitive to abrupt changes in their environments throughout their range, and that the impact of such changes is more likely related to change in prey availability than to changes in temperature per se.
Jiang, J. and Perrie, W. 2007. The Impacts of Climate Change on Autumn North Atlantic Midlatitude Cyclones. J. of Climate, 20, 1174-1186.
High resolution climate model simulations show that increased CO2 concentrations could cause storms in the northwest Atlantic to move slightly poleward toward the North Atlantic coast, to propagate faster, and to increase in size. No real tendency to become more severe is apparent. These changes could have impacts on coastal areas of North America.
Researchers investigated how autumn mid-latitude storm intensities, frequencies and tracks might change in the future in response to increasing CO2 concentrations. The authors performed relatively high resolution storm simulations using the Canadian MC2 atmospheric model driven by output from the second generation Canadian Coupled Global Climate Model (CGGCM2) under present climate and climate change conditions. The climate change scenario used the IPCC IS92a emission scenario, where CO2 concentrations are near double pre-industrial levels by about mid-century. Changes in mid-latitude storms for the 2040-2059 period are compared to present climate conditions (period 1975-1994). The results of the present study show that despite large-scale changes in environmental conditions between the two climates, future storms show about the same intensities as those of the present. However, in the future climate scenario, storms exhibit a larger horizontal extent, show a tendency to propagate faster and the storm track is shown to move slightly poleward nearer the North Atlantic coast, (a finding consistent with previous studies). A notable feature of this study was the use of a relatively high resolution model (0.25°) over the storm region compared to previous studies of the impacts of climate change on mid-latitude and high-latitude storms, which have tended to use global models.
Jiang, J. and W. Perrie, 2007. The impact of climate change on autumn North Atlantic midlatitude Cyclones, J. Climate, 20(7), 1174-1187.
Northwest Atlantic extratropical storms are projected to shift further north and cover a larger area by mid-century.
A study published in the Journal of Climate explores how extratropical cyclone intensities, frequencies, and tracks may change in the future with global warming. The authors used the Canadian mesoscale compressible community (MC2) model, driven by the Canadian Coupled Global Climate Model (CGCM2), to simulate present extratropical cyclonic activities for the northwest Atlantic, and to model what would happen under the IPCC IS92a emission scenario which represents a doubling of CO2 by 2050. The results show an increase in the storm radius, as well as a noticeable poleward shift by 2050. They also found non-statistically significant increases in storm severity and faster movement of the systems from their genesis area into the northwest Atlantic. A shift in storm track and increase in size of the system would certainly lead to an increase in the number of storms hitting land in the Atlantic region.
Kilpatrick, A.M., M.A. Meola, R.M. Moudy and L.D. Kramer, 2008. Temperature, viral genetics, and the transmission of West Nile Virus by Culex pipiens Mosquitoes, PLoS Pathogens, 4(6): e1000092. doi:10.1371/journal.ppat.1000092.
A recent study shows that higher temperatures helped a new strain of West Nile virus invade and spread across North America and that global warming could sharply accelerate transmission of the virus and possibly lead to more severe epidemics of West Nile virus in some cooler regions.
The first occurrence of West Nile virus (WNV) in the western hemisphere was in New York City in 1999. It has subsequently spread throughout much of the Americas. It is primarily transmitted between birds and Culex mosquitoes. From the period 1999-2007 the WNV has caused a total of 32,135 reported cases, 11,243 cases of encephalitis and 1,125 deaths. In addition, the WNV has evolved over these years and, in 2002, a new strain of the virus emerged and rapidly spread throughout North America, displacing the old strain by 2005. Coincident with the spread of this new strain were two of the largest epidemics of West Nile virus recorded to date in North America, in 2002 and 2003. In this recent study, the authors set out to determine how the new strain of West Nile virus had displaced the first strain, and what effect temperature had on transmission by mosquitoes. They used laboratory tests to determine how soon mosquitoes are capable of transmitting the virus after feeding on infected blood. The results showed that for both strains, increases in temperature greatly accelerated transmission of the virus by increasing the efficiency of viral replication in the mosquitoes. However, the new strain is more efficient at infecting, disseminating and being transmitted than the older strain, and the advantage of the new strain increases with higher temperatures. As a result, regional temperature increases of just a few degrees due to global warming could sharply accelerate transmission of the virus and possibly lead to more severe epidemics of West Nile virus in some cooler regions.
Laidler, G.L. 2006. Inuit and scientific perspectives on the relationship between sea ice and climate change: the ideal complement? Climatic Change (2006) 78: 407-444.
The paper, by a Canadian researcher, provides a baseline for exploring Inuit and scientific understanding of the relationship between climate change and sea ice in the Canadian Arctic. These systems of knowledge may be complementary and new modes of communication and collaboration may allow for more comprehensive assessments of community vulnerability and adaptive strategies.
Laštovicka, J., R.A. Akmaev, G. Beig, J. Bremer and J.T. Emmert. 2006. Global Change in the Upper Atmosphere. Science, Nov 24 2006.
Qian, L., R. Roble, S.C. Solomon, and T.J. Kane. 2006. Calculated and observed climate change in the thermosphere, and a prediction for solar cycle 24. GRL, Vol 33. L23705
The importance of global climate change in the upper atmosphere is drawing more attention today since the change in density of the air in the thermosphere is having a measurable affect on the drag of satellites. Two recent papers report on the secular change of the thermosphere neutral density (temperature) over the past three decades. Qian et al., show that in the upper atmosphere, the radiative effects of carbon dioxide have cooled the atmosphere to the point that the density of the air increased by 1.7% per decade at 400 km up to the year 2000. Laštovicka et al.,, however, show that this value is not constant but varies from 2.2 to 2.9% per decade at solar minimum while during solar maximum it varies by about 0.7% per decade. The authors' modeling work shows that during the next solar cycle, the thermospheric neutral density should increase by 2.7% per decade at 400km, which is larger than the trend over the past three decades. The clear message from these two papers is that the anthropogenic emissions of greenhouse gases impact all levels of the atmosphere, affecting not only life on the surface but also the space-based technological systems on which we increasingly rely.
Lobell, D.B., M.B. Burke, C. Tebaldi, et al., 2008. Prioritizing climate change adaptation needs for food security in 2030. Science Vol 319 February 1 pp607-610.
Probabilistic projections of climate impacts on agricultural production, in regions where food security is at risk, reveals that some high risk areas and crops can be identified with considerable confidence. Such projections provide decision-makers with useful information for developing appropriate risk management strategies.
A study published recently in the journal Science provides an approach to prioritizing climate change adaptation needs for food security. The study assessed climate risks for crops in 12 major food-insecure regions identified by the UN Food and Agriculture Organization. Three specific criteria for assessing climate related crop risks were selected: 1) the importance of a crop to the diet of the food-insecure population, 2) the median projected impact of climate change on crop production in 2030 (multi-model evaluation), 3) the 5th and 95th percentiles of projected impacts representing worst and best case scenarios, respectively, from among the ranked projections. Probabilistic projections of climate change impacts on crops are provided using statistical crop models developed from historical analyses of crop harvest and climate relationships, combined with future temperature and precipitation projections from 20 GCMs. Projections of average temperature change for 2030 were around +1°C in most regions, while results for precipitation change showed far more variability among regions, and greater uncertainties within regions. High risk areas are identified as being those crop-region combinations of high importance for which impacts are projected to be consistently negative, and included South Asia wheat, Southeast Asia rice, and Southern Africa maize. These cases generally arose from a strong historical dependence of crop harvest on temperature combined with projected warming large enough to overwhelm precipitation change uncertainty. However, the full suite of probabilistic projections provides useful data for developing alternative approaches to adaptation based on different risk management priorities.
Lobell, David, B. and Field, Christopher, B., 2007. Global scale climate-crop yield relationships and the impacts of recent warming. Environmental Research Letters 2(1): 014002, 7 pages.
Negative impacts on crops associated with recent warming between 1980 and 2002 have very likely offset some of the yield gains associated with rising CO2 and technological advances.
A recent paper by researchers in California evaluated the global-scale net effect of climate change on crop yields for the world's six most widely grown crops (wheat, maize, barley, rice, soy and sorghum). The authors used simple measures of growing season temperatures and rainfall - spatial averages based on the location and coverage of each crop - and showed that nearly 30% of the year to year variation in global average crop yields could be explained by these simple measures. The study also showed that the negative impact of climate warming on yield was most pronounced for wheat, maize and barley over the period of 1980 to 2002 and less so for the other three crops and decades. Negative yield impacts for wheat, maize and barley were deemed to be small but significant, with substantial absolute losses in global production resulting from recent warming. Therefore, the authors conclude that warming from 1981-2002 has very likely offset some of the yield gains from rising CO2 and technological advances and other non-climatic factors. This conclusion suggests that some caution should be used in accepting model assessments showing global crop benefits for warming up to about 2°C.
Malcolm, J.R., C. Liu, R.P. Neilson, L. Hanson, and L. Hannah. 2006. Global warming and extinctions of endemic species from biodiversity hotspots. Conservation Biology 20: 2: 538-548.
This study, by University of Toronto scientist Jay Malcolm and international colleagues, assesses climate change impacts on terrestrial biodiversity at the global scale. The authors focus on the vulnerability of 25 global biodiversity hotspots - areas that are home to a disproportionate number of the world's species and have experienced considerable habitat loss already. They used equilibrium distributions of the major vegetation biomes under a doubling of CO2 concentrations and, based on changes in areas and distributions of the major biomes within the hotspots, used species-area relationships to project numbers of extinctions of endemic plant and vertebrate species from these hotspots. Output from 14 models combinations were used: seven GCMs and two global vegetation models. Projected percent extinctions ranged from <1 to 43% of the endemic biota, with results depending largely on assumptions about species' migration capabilities, breadth of tolerance for habitat change, specificity of habitat requirements and the vegetation model used. Among these four sensitivity factors, biome specificity had the greatest influence on projected extinctions. Only a few hotspots showed climate change related habitat loss that was significantly different than random same-biome collections of grid cells. The implications of this are that while biodiversity hot spots may not be more vulnerable to climate change than other areas, the high species extinction rates projected for hotspots could be equally applicable to other areas as well, where species have restricted geographic ranges (i.e. biome specificity).
Mareuil, A., R. Leconte, F. Brissette and M. Minville, 2007. Impacts of climate change on the frequency and severity of floods in the Châteauguay River basin, Canada. Can. J. Civ. Eng. 34: 1048-1060.
A recent study looking at the potential effects of climate change on the flood regime of the Châteauguay River basin in Southern Quebec provides some evidence of reduced flood risk in the future, although results vary quite significantly depending on the GCM used.
In a recent paper, the potential effects of climate change on the flood frequency and severity (peak flows) in the Châteauguay River basin (CRB) are investigated through a series of hydrologic modelling experiments (model HSAMI) driven by three GCMs (HadCM3, ECHAM4 and CGCM2). Monthly temperature and precipitation values, both for current (1960-1990) and future (2040-2060, under the SRES-B2 scenario) climate were extracted from the GCMs, then were used to drive a stochastic weather generator (WeaGETS) that produces daily times series of precipitation and minimum and maximum air temperatures. A total of 200 climate scenarios were produced using WeaGETS and linked to the HSAMI hydrological model: 50 for the current climate and 50 for the future climate for each of the three GCMs. For each scenario, maximum spring and summer-fall flow values were extracted and a flood frequency analysis was performed, for flood return periods between 2 and 500 years. The results show that changes in the future hydrological regime of the CRB depend strongly on the GCM used, with future spring peak flows almost similar to the current ones with HadCM3, but statistically reduced with ECHAM4 (by an average of 30%) and CGCM2 (8% on average). The reductions in peak spring flows occurred even though future climate with all three models was generally wetter in spring (as well as warmer). The results obtained support the hypothesis that spring flow variability depends more on temperature than on the precipitation regime. All the GCM-derived scenarios project an earlier onset of the spring melt and of the spring peak flow. As for summer-fall peak flows, the results also differ depending on the GCM, with future peak flows changing very little with HadCM3, statistically reduced with ECHAM4 (12% on average), and reduced (6%) but not in a statistically significant way (except for return periods of 100 and 500 years), with CGCM2. There is less confidence in the summer-fall projections, however, given the known underestimation of extreme precipitations events by WeaGETS.
Mendelsohn, R. and Reinsborough, M., 2007. A Ricardian analysis of US and Canadian farmland. Climatic Change 81: 9-17.
The effects of climate change on agriculture will vary significantly between Canada and the United States, with Canada benefiting from increased precipitation while American farms would be highly sensitive to higher temperatures.
A joint Canada-US study was undertaken to hypothesize the climate response of croplands to a hypothetical warming scenario based on present data. Using a Ricardian model technique to assess the effects of climate on cropland value, and climate data from 1961 to 1990, the authors found that the effects of warming on farm value would vary considerably between the two countries. Results showed that although the response of Canadian farms to warmer temperatures is unclear, they would benefit from increased precipitation. While American farms may also benefit from increased precipitation, land value will be significantly decreased by the negative effects of warmer temperatures. The results suggest that for agriculture, midlatitude regions are more vulnerable to warming than polar ones but it also raises questions as to whether certain variables may be overlooked by the model.
Moore, S.E. and H.P. Huntington. 2008. Arctic marine mammals and climate change: impacts and resilience. Ecological Applications, 18(2) Supplement, 2008, pp. S157-S165.
A special issue of Ecological Applications is dedicated to assessing the effects of climate change on Arctic marine ecosystems and mammals. The papers review the current status of marine mammals, assess the overall impacts and species resilience, and examine potential conservation measures.
The rapid shift in environmental conditions is challenging the adaptive capacity of Arctic marine mammals especially those reliant on sea ice (polar bear, walrus and ringed and bearded seals). The synthesis paper of this special issue of Ecological Applications constructs a conceptual model of the potential impacts of climate change on arctic marine mammals based on sea ice loss or gain. The authors examine the possible responses to sea ice change of these four ice-obligate species together with seven ice-associated species (other seals and some whales) and five seasonally migrant species (other whales). The ice-obligates rely on sea ice as a platform for hunting, breeding and resting and their species fitness has been correlated to seasonal and temporal extent and thickness of sea ice. The polar bear provides the clearest example --reduction in sea ice removes their hunting and resting platform and reduces survivorship for ringed seals, their primary prey. For bowhead whales, an ice-associated species, loss of sea ice may enhance their feeding opportunities with the possible influx of more prey. To investigate resilience of the 16 species in this paper the authors divide the Arctic into four sectors reflecting the regional nature of temperature and sea ice changes. This analysis showed that species within the Canadian Archipelago may be more resilient to climate change due to fewer ice free days and the occurrence of sea ice refugia than those in other regions. Given that there is insufficient knowledge regarding population dynamics and that satellite techniques are limited to providing broad scale observations, the traditional knowledge of subsistence communities can provide a first-line of investigation into changes in marine mammal populations. Future research directions point to indicator development using sentinel species based on population census, satellite tracking, and monitoring through documenting local harvest and knowledge.
Ogden, N.H., A. Maarouf, I.K. Barker et al., 2006. Climate change and the potential for range expansion of the Lyme disease vector Ixodes scapularis in Canada. Int. J. Parasitology 36:63-70.
Canadian researchers investigated the potential expansion of the geographic range for the Lyme disease vector I. scapularis in the future under climate change. Mean annual degree days > 0°C (DD>0°C) were previously found to be a useful index for mapping temperature conditions suitable for I. scapularis. Using both the CGCM and HadCM3 models and the A2 and B2 emissions scenarios, authors mapped the DD>0°C in Canada and found that a range expansion is evident as early as the 2020s in southern Saskatchewan, Manitoba, Ontario, Quebec, most of New Brunswick and all of Nova Scotia and PEI. By 2050, both models and both emissions scenarios projected a potential range covering most of Canada east of the Rockies and south of 50°N. After the 2050 period, the differences between the A2 and B2 emissions scenarios were evident with the B2 scenario showing a lower rate of range expansion. In the 2080 time period, temperatures in most of central and eastern Canada south of 53°N and Newfoundland were projected to be suitable for I. scapularis. Authors conclude that this range expansion is likely to lead to an associated expansion in the risk of Lyme disease in Canada.
Parkins, J.R. and N.A. MacKendrick. 2007. Assessing community vulnerability: A study of the mountain pine beetle outbreak in British Columbia, Canada. Global Env Change 17: 460-471.
An assessment of community vulnerability to the Mountain Pine Beetle outbreak in British Columbia shows that risk varies between communities with some displaying vulnerability to physical risk while others are more vulnerable to economic risk.
Researchers with the Canadian Forest Service have developed a vulnerability assessment model that brings together theoretical ideas from the climate science literature and the community capacity literature, in an effort to determine vulnerability at a community level. This model was then applied to the mountain pine beetle (MPB) outbreak in British Columbia. The authors argue that this assessment of vulnerability at the community scale is preferable because the community or local scale is that at which policy action takes place, and that community-scale assessment also provided information on variations in vulnerability that can be lost at national or regional scale studies. For instance, the study found that for several communities, although a high level of physical risk from devastation by an MPB outbreak was apparent, vulnerability was tempered by political and economic factors. Meanwhile, in other communities, a high level of economic risk heightened vulnerability. The main thrust of this paper was to present to readers a detailed framework for local vulnerability analysis that showed the myriad of factors at the local level which influence vulnerability.
Parmesan, C. 2007. Influences of species, latitudes and methodologies on estimates of phenological response to global warming. Global Change Biology 13: 1860-1872.
A new study indicates a consensus may be forming around the estimated mean global advancement in the timing of spring events across all taxa, with that estimate being between 2.3 and 2.8 days per decade advancement. Significant differences in the magnitude of the response were evident across species, with amphibians in particular showing the strongest response by far.
Many studies have been published documenting changes in phenology among plant and animal species in response to regional climate warming. Although the vast majority of such studies demonstrate that species are responding as expected, the magnitude of the response varies by an order of magnitude across species. There is the possibility that some of this difference in response among species may be due to differences in study design and statistical analysis methodology. This study set out to explicitly test this hypothesis using the only two existing, quantitative, globally comprehensive datasets of phenological responses to recent climate warming - papers published by Root et al., and by Parmesan and Yohe, both in 2003. Specifically, Parmesan set out to determine the cause of the more than two-fold difference in estimates of the mean global advance in timing of spring events between the two studies: 2.3 days per decade found by Parmesan and Yohe and 5.1 days per decade found by Root et al., The results showed that the difference in estimated response is primarily due to the use of different criteria for incorporating data by the two studies. Once these differences are accounted for, the studies generated more similar conclusions despite analyzing substantially different datasets. The author then presents analysis of a new, expanded dataset of 203 species. These and the other results together indicate a consensus estimate of mean response between 2.3 and 2.8 days per decade advancement of spring events across all taxa globally. Amphibians had a significantly stronger shift toward earlier breeding than all other taxonomic groups, advancing more than twice as fast as trees, birds and butterflies, and nearly eight times as strong as that for herbs, grasses and shrubs. The author suggests this may be due to the sensitivity of amphibians to changes in precipitation as well as changes in temperature. Of particular interest is that although the study did show a stronger response at higher latitudes, latitude did not explain much of the variability in phenological response.
Rahmstorf, S., 2007. A semi-empirical approach to projected future sea-level rise. Science. 315, 368-370.
Study suggests sea-level rise could be almost double IPCC forecast for the next century.
German scientist Stefan Rahmstorf, in a Science magazine article, correlates the changes in temperature with the changes in sea-level rise over the period 1880-2001 to show a rise of about 3.5 mm/year per °C. Assuming little change in the physics behind the trend over the next hundred years, and using IPCC temperature projections, he uses this relationship to project a range of sea-level rise by 2100 of between 0.5m and 1.4m. By comparison, the IPCC Third Assessment Report presented projections of sea-level rise, based on global climate model results, of between 0.09m to 0.88m by 2100. The above differences suggest a continued need for improvement in understanding the aggregate impacts of the various processes that contribute to sea-level rise.
Reagan, M.T. and G.J. Moridis. 2007. Oceanic gas hydrate instability and dissociation under climate change scenarios. GRL Vol 34, L22709, doi:10.1029/2007GL031671.
Shallow methane hydrate deposits in the arctic are shown to be the most sensitive to ocean warming.
Methane gas hydrates locked in sediments under the ocean floor are known to constitute a very large reservoir of carbon (methane) which, if released in response to ocean warming, could produce strong positive feedbacks on the climate system. A study published in GRL investigated the dynamic response of three different types of hydrate deposits to three ocean warming scenarios over the next 100 years. The three simulated deposits were representative of: typical deep-ocean stable hydrate; warm, shallow, Gulf of Mexico deposits; and cold, shallow deposits on the arctic continental shelf. Increases in temperature at the seafloor of 1°C, 3°C and 5°C over 100 years were simulated. The deep cold hydrates (at 1000m depth) were shown to be stable to all three temperature change scenarios. The shallow deposits were shown to be responsive to ocean warming, undergoing rapid dissociation and producing significant methane fluxes into the ocean. The strongest reaction was from the shallow, cold deposits representative of arctic continental regions where methane fluxes were shown to be 5 to 8 times larger than the rates of benthic sediment methane oxidation. Hence much of the methane reaches the top of the sediments and escapes into the sea water above. The results of this study confirm the stability of deep ocean hydrates but underscore that the greatest potential impact of ocean warming would be on shallow hydrates, particularly in arctic regions, where warming is expected to be strong, and deposits are both thick and shallow and readily destabilized. The consequences of such methane fluxes to ocean ecosystems is not known and further work is needed to estimate the quantity of methane releases that would reach the atmosphere.
Reid, S., B. Smit, W. Caldwell and S. Belliveau. 2006. Vulnerability and adaptation to climate risks in Ontario agriculture. Mitig Adapt Strat Glob Change DOI 10.1007/s11027-006-9051-8.
Through the use of focus groups and interviews, Ontario researchers investigated the vulnerability and potential for adaptation to climate change among farmers in Perth County, Ontario. Weather conditions, including excessive precipitation and drought, timing of precipitation and growing season temperature, were regularly cited as being important for crop success, along with non-climatic forces such as commodity price. Perceptions of climate change were also surveyed and this revealed that climate change is seen as a long term issue and many respondents (42%) were entirely unconcerned with the issue at present. While farmers in Perth County have considerable capacity to adapt to current climate variability, some changes in climate, such as new pest outbreaks or increased frequency or severity of drought, would severely test their adaptive capacity. The authors conclude that enhancement of the region's ability to deal with climate change would likely require action beyond the control of individual producers to include the involvement of public agencies, awareness raising initiatives, policy review, insurance programs and technological developments.
Rignot, E. and Kanagaratnam P. 2006. Changes in the Velocity Structure of the Greenland Ice Sheet. Science 311: 986-990.
Rignot and Kanagaratnam used satellite radar interferometry data to measure the change of glacial velocity of Greenland between 1996 and 2005 due to the artic warming in the last decade. Results indicate that the flow of several large glaciers accelerated, which extended from southeast and northwest in 1996 to 2000 to central east and west in 2005. Moreover, the affected area expanded rapidly from below 66°N to 70°N during the study period. This glacier acceleration drains the Greenland Ice Sheet to the sea. In addition to increasing surface melting and runoff under a warmer climate, all these factors enhance further melting of the Greenland Ice Sheet. The authors estimated that the ice loss of Greenland doubled in the last decade from 90 to 220 km3/yr, which is equivalent to 0.23 to 0.57 mm/year of sea-level rise. As current models do not include the factor of current glacial acceleration in Greenland, Rignot and Kanagaratnam believed that model projections can only provide lower limits to the potential contribution of Greenland to sea level rise.
Scheffer, M., V. Brovkin and P.M. Cox. 2006. Positive feedback between global warming and atmospheric concentration inferred from past climate change. GRL 33, L10702, doi: 10.1029/2005GL025044.
An important uncertainty in climate change projections relates to effects of increasing temperature on the carbon cycle, and hence on atmospheric CO2 concentrations. A limited number of coupled climate-carbon models have taken this ecosystem feedback into account, with results suggesting an overall amplification of the effects of rising levels of GHGs (i.e. a net positive feedback effect). However, the magnitude of this feedback remains poorly understood. In this paper, Scheffer et al., compare changes in temperature during the Little Ice Age reconstructed from paleo data with concurrent changes in CO2 concentrations (allowing for a 50 year lag) to estimate the possible range for this feedback. They assume the changes in CO2 concentrations were entirely a response to the changes in temperatures. Allowing for uncertainties in temperatures change estimates, this implies that biological feedbacks cause a change in atmospheric CO2 concentrations of between 12 and 41 ppmv per C. They estimate that including the ecosystem feedback in warming projections could increase potential warming over the next century due to human emissions of greenhouse gases by an additional 15-78%.
Schwartz, Mark W., Louis R. Iverson, Anantha M. Prasad, Stephen N. Matthews and Raymond J. O'Connor, July, 2006. Predicting extinctions as a result of climate change. Ecology 87(7): 1611-1615.
It has previously been demonstrated that climate change may have a very large impact on biodiversity. In this study, the authors attempt to characterize the efficacy of using bioclimatic models to assess climate change's possible extinction potential. This is done with a special focus on species with small geographic distributions. Previous work has demonstrated that species with small geographic distributions are predicted to experience a higher degree of range displacement, and therefore higher risk of species extinction. This phenomenon is examined in this study, as well as the tendency of bioclimatic models to exhibit poor fit for narrowly distributed species. Data for 142 tree and 116 bird species are used with climate, vegetation and environment variables to develop regression models for habitat suitability. These models are then used with doubled-CO2 climate projections from the Hadley and Canadian Climate Center GCMs to determine the effect of range size on model fit. The authors find that range size for both trees and birds was correlated significantly with overlap of current and predicted future ranges. Species with small current ranges are more likely to have future distributions that are separated from their current distribution, and are therefore at a higher extinction risk. Range size was also positively associated with model fit, with small-range species showing poorer model fit. The authors suggest some reasons for this effect of range on model fit. The small number of observations possible with narrowly distributed species creates low statistical power; also, some narrowly distributed species can be constrained primarily by non-climatic factors, reducing the ability of bioclimatic models to successfully explain their distribution. The authors point out the conservation dilemma illustrated by their models: sparse and endemic species are among the most likely candidates for climate change-related extinction, but also the ones that are most difficult to model accurately.
Scott, Daniel and Brenda Jones, 2006. The Impact of Climate Change on Golf Participation in the Greater Toronto Area (GTA): A Case Study Journal of Leisure Research 38(3): 363-380.
This paper, by two University of Waterloo geographers, includes the development of a statistical model relating weather to golf participation in the GTA, and the use of that model to make estimates of golf participation under two different climate change scenarios. The authors first obtained two years of golf participation data for a local golf course, and then data on weather variables from the Pearson airport weather station. These variables were used to derive an equation relating number of rounds played in a given day to maximum and minimum daily temperatures, daily precipitation and day of the week. The regression model was then run with observed 1961-1990 weather data to obtain a climatological baseline (which the authors emphasize was not meant to represent a model of actual 1961-1990 golf participation). Finally, the regression model was run with weather variables obtained by downscaling GCM outputs from two different scenarios (NCARPCM B21 and the more extreme CCSRNIES A11) for the 2020s, 2050s and 2080s. Downscaling was done using the Long Ashton Research Station stochastic weather generator. Importantly, several weather variables (including timing of precipitation and wind speed) were found to be relevant to golf participation but were not included in the model because they could not be obtained from downscaled GCM outputs. In addition, the inclusion of day of the week in the regression model is questionable, since frequency of any given day of the week will be invariant under climate change (although extending season length may result in some impact due to the inclusion of different days of the week). In both scenarios, number of rounds played for a given season length increased under climate change, from 5.5% in the 2020s under the mild scenario to 28.4% in the 2080s under the more extreme scenario. When the adaptation measure consisting of extended season length was taken into account, rounds played increased by 23% in the 2020s under the mild scenario and 72.7% in the 2080s under the more extreme scenario. By the 2080s in the most extreme scenario, the potential exists for a year-round golf scenario (with some intermittent play in the coldest months), as is the case in the considered geographical analogue of Columbus, Ohio. The authors point out that many non-climatic factors will influence golf participation in the future, but their results may nevertheless be useful and extended generally to other climatically-similar regions like Southern Quebec.
Scott, D., Jones, B. and Konopek, J. 2006. Implications of climate and environmental change for nature-based tourism in the Canadian Rocky Mountains: A case study of Waterton Lakes National Park. Tourism Management 28: 570-579.
A recent Canadian paper considered the impacts of climate change on visitation rates over the next century for Waterton Lakes National Park (WLNP) in Alberta. The study indicated that until at least the mid-century, the warming effects of climate change would benefit the tourism industry but that in the latter part of the century, visitation is expected to decrease due to changes in the attractiveness of the Park's landscapes.
Canadian researchers analysed monthly recorded visitation data for Waterton Lakes National Park (WLNP) in Alberta, for the 1996-2003 tourist seasons as well as monthly climate data from the Lethbridge meteorological station. From these data, a regression-based climate-visitation model was developed and used in conjunction with future climate simulations to project climate change impacts on tourism for this National Park. The study also used visitor surveys to evaluate how climate change related impacts on the natural landscape would affect future visitation rates. Model results showed that for the 2020s, and 2050s, an increase in visitation is projected (6-11% and 10-36% for the two time periods respectively) due primarily to a lengthening of the warm-weather tourism season. Despite some landscape changes, the visitor survey revealed that these would likely have minimal impact on visitation for these time periods. Toward the end of the century, however, the impact of changing landscapes on tourism becomes more significant. While the climate-visitation model showed an even greater increase in visitation for the 2080s (11 - 60%) based on changes in climate, 56% of respondents indicated that they would no longer come to the park or would visit less often if the very substantial landscape changes projected for the 2080s were realized. This included a loss of glaciers, a tripling of grassland habitat and major increases in the risk of forest fires (with associated campfire bans). The results suggest them that long-term environmental changes may diminish the attractiveness of the Park in ways that may offset potential gains in visitation from an extended warm-weather tourism season.
Smol, J.P and M. S. V. Douglas. Crossing the final ecological threshold in high Arctic ponds. PNAS Early Edition doi_10.1073_pnas.0702777104.
High Arctic ponds cross another ecological threshold with reduced water levels and desiccation with consequences for Arctic biodiversity.
Two Canadian scientists have conducted systematic monitoring of 24 high Arctic ponds from 1983 to 2006 at Cape Hershel on Ellesmere Island. These ponds, being located on granite, are not subject to permafrost melt and have been a permanent feature of this landscape for millennia functioning as biodiversity hotspots. Earlier research of these high Arctic lakes by the authors showed ecological changes that began in the 19th century consistent with regional warming indicating longer ice free periods, and with associated limnological changes. The research in this paper found evidence of lower water levels and, in some ponds, complete desiccation, as well as changes in water chemistry. Over the study period, pond water exhibited increasing conductivity reflecting increased evaporation relative to precipitation. Consequences for the biota in the ponds and the surrounding wetlands are likely to be severe. By linking the long term data with current observations of lake desiccation, the authors conclude that trends that began in the 19th century greatly accelerated in recent decades in response to strong regional warming. This paper does not, however, discuss the causes of regional warming trends although other work has indicated an anthropogenic component to recent Arctic warming. The authors propose that a key "tipping point" has been passed: once-permanent Arctic ponds are now ephemeral with cascading effects through the Arctic ecosystem (e.g. waterfowl habitat and breeding grounds, invertebrate population dynamics, drinking water for wildlife).
Stammer, D. 2008. Response of the global ocean to Greenland and Antarctic ice melting. JGR Vol 113, C06022, doi:10.1029/2006JC004079. 16 pp.
Water from melting of Greenland's ice cap is shown to remain for the most part in the Atlantic Ocean over a 50-year period, with only limited effects elsewhere. Ice melting from Antarctica is expected to propogate even more slowly through the global ocean.
The recently increasing melt rates from both the Greenland and Antarctic ice sheets have spurred much discussion about the potential consequences for global sea level rise. Implicit in such discussions is the notion that it will take some time for additional melt water from the ice sheets to move through the various ocean basins, but the time component of global sea level rise is not often discussed. A paper published recently in the Journal of Geophysical Research examines this issue in particular, investigating the transient response of regional and global oceans to enhanced freshwater input associated with melting of the Greenland and Antarctic ice sheets. The investigators use the MIT ocean general circulation model for their experiments. Their experiments consisted of a control run and two subsequent runs in which the freshwater forcing was perturbed locally in two separate regions, one centred around Greenland and one around Antarctica. In both perturbation runs, freshwater anomalies were added through-out a 50-year simulation period mimicking enhanced run-off of Greenland and Antarctic melt water. The results of this work confirmed earlier studies suggesting that the global ocean is less sensitive to perturbations to the southern ocean than to the North Atlantic. Timescales for a first response of the Atlantic to increased freshwater runoff from Greenland were shown to be just a few years for the subpolar North Atlantic and 5-10 years for the Atlantic and global ocean. However, no equilibrium was reached at the end of the 50-year run and within this time period, most of the sea level increase associated with freshwater input from Greenland remained in the Atlantic Ocean. This, the authors note, is an important result since it suggests that melting of Greenland's ice cap is much less of a threat to tropical islands in the Pacific than it is for the coasts of North America and Europe.
Stirling, I., and Parkinson, C.L. 2006. Possible Effects of Climate Warming on Selected Populations of Polar Bears (Ursus maritimus) in the Canadian Arctic Arctic Vol. 59, No. 3 p. 261-275.
In 2005, harvesting quotas for polar bears in Nunavut were increased, on average by 28 percent, based on evidence that populations were growing. Inuit tradition knowledge - primarily increased sightings near settlements - was a key piece of evidence. This study used satellite sea-ice cover data (1979-)and female polar bear mass data (1980-) for five Canadian polar bear populations (Western Hudson Bay, Foxe Basin, Baffin Bay, Davis Straight, and Eastern Hudson Bay) to draw the following conclusions about the relationship between sea ice and future population health. In three of the five regions, statistically significant and progressively earlier sea-ice break-up is occurring. Population and harvest data for Western Hudson Bay and Baffin Island indicate that polar bear populations are likely to be declining. In four of the areas, the number of "problem" bears correlates with earlier season ice breakup and the physical condition of the bears. The increased sightings might therefore relate to hunger and not population increases. Preliminary evidence for Western Hudson Bay and Davis Straight suggests that harp seals (prey species) may also be affected by climate changes and are no longer increasing. The evidence, taken together, suggests that a precautionary approach ought to be followed for polar bear harvests.
Stramma, L., G.C. Johnson, J. Sprintall, and V. Mohrholz. 2008. Expanding oxygen-minimum zones in the tropical oceans. Science Vol 320, 2 May 2008, pp655-658.
Areas of the tropical oceans with depleted oxygen concentrations are shown to have expanded over the last 50 years. Changes in dissolved oxygen concentrations have fundamental implications for the survival and fitness of marine organisms.
Dissolved oxygen concentrations are a critical factor in determining the distribution of marine organisms since organisms become stressed or die when oxygen levels drop below critical thresholds. Climate models predict an overall decline in oceanic dissolved oxygen concentration and an expansion of the oxygen minimum zone (OMZ) with global warming. This study reports on observed changes in dissolved oxygen concentrations in select areas of the tropical oceans. Historical data were augmented with data recently collected from those few ARGO floats outfitted with oxygen sensors. Tropical ocean OMZs in the central and eastern tropical Atlantic and equatorial Pacific Oceans appear to have expanded and intensified (i.e. oxygen minimum concentrations are lower than before) during the last 50 years. Of particular interest is that the decline in oxygen content has been most intense in the tropical Atlantic where, compared to the Pacific and Indian Oceans, low oxygen areas (hypoxic areas) are comparatively small at present. This would suggest that the Atlantic has the potential for large increases in hypoxic areas with potentially negative consequences for marine organisms in the region. The results of this study support climate model predictions that oxygen-depleted zones in the ocean will expand under global warming conditions; however, this study does not attribute the observed changes to global warming. The authors attribute the expansion of the OMZs to a combination of thermal, dynamic and biogeochemical factors.
Suttle, K.B., Meredith A. Thomsen, Mary E. Power (2007), Species Interactions Reverse Grassland Responses to Changing Climate, Science, vol. 315, pp.640-642.
An experiment in grassland fields in Northern California has shown that for altered rainfall regimes under a changing climate, the timing of seasonal rainfall has a larger effect than the amount of rain. Surprisingly, the study also found that more rain at the beginning of a usually dry season can lead, after a few years, to a decline in the diversity and abundance of the species.
A five year experiment in Northern California was done to get a better understanding of grassland species' (plants and invertebrates) response to climate change. The experiment reproduced two very different projected future precipitation regimes: one with additional rainfall during the current winter rainy season and, one with increased spring rainfall extending into the currently very dry summer. The results show that while adding more rain in winter produced only moderate changes in plant production, extending the rainy season in spring produced much more dramatic changes in the entire grassland community. These changes were positive in the first two years, with large increases in plant production and diversity. However, as altered conditions persisted over the years, steep declines in plant species richness were observed, affecting the diversity and abundance of invertebrate herbivores, predators and parasitoids. The authors conclude that any prediction of ecological effects under different climate scenarios will require multi-year experiments to get a better understanding, not only of individual species which have a fast direct response to climate change, but also of the effects of altered interactions between species within an ecosystem.
Tarnocai, C. 2006. The effect of climate change on carbon in Canadian peatlands. Global and Planetary Change 53:222-232.
Tarnocai uses the updated Peatlands of Canada Database (published in 2002 by the Geological Survey of Canada) and a peatland sensitivity model (under a 2xCO2 scenario; see Kettles and Tarnocai, 1999) to assess the sensitivity of various peatland classes to climate change and to evaluate the amount of organic matter in sensitive peatlands. Peatlands contain about 147Gt of soil carbon, which is about 56% of the organic carbon stored in all Canadian soils. The author finds that approximately 60% (675 thousand km2) of the total area of Canadian peatlands, and 51% (75Gt) of the organic carbon in all Canadian peatlands, fall in the two highest sensitivity classes (those expected to be 'severely' or 'extremely severely' affected by climate change). About half of this organic carbon is in perennially frozen peatlands, while the other half is in unfrozen peatlands. The author suggests that with warmer temperatures, the thawing of ice-rich peat will likely lead to water saturated conditions and release of methane through anaerobic decomposition, while thawing of peatlands containing little ice is more likely to lead to dry soil conditions and release of carbon dioxide.
Turetsky, M.R., R.K. Wieder, D.H. Vitt et al., (2007). The Disappearance of Relict Permafrost in Boreal North America: Effects on Peatland Carbon Storage and Fluxes, Global Change Biology, 13:1922-1934.
A study investigating the consequences of surface permafrost degradation in boreal peatlands in Canada shows that the net effect of changes in carbon sequestration and methane emissions is likely to be neutral for at least 70 years, after which a small net C sink is expected.
For many thousand of years, boreal peatlands, which are a common type of wetland in boreal regions, have been an important reservoir (sink) for atmospheric carbon. In Northern regions, peatlands are often underlain by permafrost and, as a consequence of the warming climate, permafrost features are degrading, leading to increased saturation of soil layers and peat surface collapses. The consequences for changes in carbon storage are of great interest because of the potential for feedbacks on the climate system. In this study, a team of scientists studied peatland sites at the southern edge of permafrost occurrence in Western Canada, to determine the influence of different permafrost regimes on peat accumulation rates and on CO2 and CH4 fluxes. Three peat landforms were assessed: unfrozen bogs, areas of degraded permafrost and bogs with localized permafrost features. They found that peat accumulation rates are larger in unfrozen bog (and those with degraded permafrost) than in permafrost peat landforms, which suggests that surface permafrost degradation stimulates net carbon storage in peatlands (through enhanced plant productivity), particularly in the first 60-100 years post-thaw. However, they also found that water-saturated conditions created by surface permafrost degradation stimulated CH4 emissions. The authors estimate that these emissions, in terms of radiative forcing, could offset the enhanced peatland carbon sink for at least 70 years following permafrost degradation. Over longer time scales, with expected changes in vegetation, soil conditions and carbon cycling, the authors suggest that the degradation of permafrost in Canadian boreal peatland is likely to represent a small net C sink.
Vautard, R., Yiou, P., D'Andrea, F. et al., 2007. Summertime European heat and drought waves induced by wintertime Mediterranean rainfall deficit. Geophysical Research Letters, Vol 34, doi:10.1029/2006GL028001
A European study indicates that the risk of extreme summer heat and drought waves in continental Europe is increased when preceded by winter rainfall deficits over Southern Europe.
Heatwaves are expected to increase in the future with global warming but the mechanisms by which extreme events, such as the European heat wave of 2003, develop are still under investigation. A recent paper looked for linkages between hot summers in Europe and regional climate anomalies in the preceding seasons. The authors used historical weather station data from across Europe to investigate the climate of the ten hottest summers between 1948 and 2005. All hot summers showed a simultaneous rainfall deficit. Furthermore, the analysis of rainfall during the preceding winter and spring seasons showed no rainfall anomaly over Northern Europe but a significant deficit over the Mediterranean areas. The authors suggest that this flow northwards in early summer of dry, warm and less cloudy air masses induces a positive feedback on the climate. That is because local evapotranspiration is increased and more water is removed from the soil. The robustness of the northward propogation of Mediterranean drought is then confirmed by the authors with regional climate model simulations over Europe. The results showed that winter rainfall deficit in Southern Europe is a necessary but not sufficient condition for the development of general summer heat and subsequent episodic heat waves in central and northern Europe.
Vecchi, G.A. and B.J. Soden (2007). Effect of remote sea surface temperature change on tropical cyclone potential intensity. Nature, 450 (7172), 1066-1070, plus supplementary information.
Local changes in sea surface temperature may have a larger effect on the response of tropical cyclone activity than the more uniform pattern of greenhouse gas-induced warming.
The response of tropical cyclone activity to global warming has been widely debated in the last few years. While it is recognized that warmer sea surface temperatures are favourable for the development and intensification of tropical cyclones, the vertical properties of the atmosphere are also important. In this recent study, Vecchi and Soden use climate models and observational reconstructions to explore the relationship between changes in sea surface temperature (SST) and tropical cyclone "potential intensity" (PI), a measure that provides an upper bound on cyclone intensity and can also reflect the likelihood of cyclone development. For regions between 30°N and 30°S, they find that regions that warm more than the tropical average are characterized by increased PI, and vice-versa. However, they also find that localized SST changes, often driven by internal modes of climate variability (e.g. ENSO) are more effective at altering PI (per unit local warming) than relatively uniform temperature changes. Thus, even in the presence of warming ocean temperatures, the internal modes of climate variability should have a substantial impact on tropical cyclone activity.
Velicogna, I. and J. Wahr. 2006. Measurements of Time-Variable Gravity Show Mass Loss in Antarctica. ScienceExpress 2 March 2006, 10.1126/science.1123785.
Using the Gravity Recovery and Climate Experiment (GRACE) satellite, this study gives, for the first time, a comprehensive survey of the entire Antarctica ice sheet. Based on 34 monthly estimates of gravity fields, between April 2002 and August 2005, the authors estimate the mass change of the Antarctic ice sheet, as a whole, and of East Antarctic ice sheet (EAIS) and West Antarctic ice sheet (WAIS) separately. The authors correct the GRACE fields for internal errors, then for external leakage like continental hydrology outside Antarctica and ocean mass variability, and finally for post-glacial rebound (PGR) effects, which are as large as the ice variability (in the order of 192 ± 79 km3/year). They find that the Antarctica ice sheet mass decreased significantly between the summers of 2002 and 2005, at a rate of 152 ± 80 km3/year. This rate of loss corresponds to 0.4 ± 0.2 mm/year of global sea level rise. The results for EAIS and WAIS are respectively, for the same period, of 0 ± 56 km3/year and 148 ± 21 km3/year. This confirms the results of other studies that have showed important mass losses of WAIS.
Wang, M. and E. Overland. 2009. A sea ice free summer Arctic within 30 years? GRL Vol 36, L07502, doi.10.1029/2009GL037820. 5pp.
A new study that takes current sea ice conditions as a starting point projects a largely sea ice free Arctic in late summer in about 30 years.
September 2008 was a milestone in that it marked two consecutive years of extreme minimum Arctic summer sea ice coverage since satellite records began. The average of the two minima is 4.5 M km2, a value that is 37% below the average sea ice extent for the period 1980-1999. These extreme summer sea ice losses are occurring much sooner than most global climate models project. Of particular interest, is the fact that many of those same model projections show an increase in the rate of sea ice loss when sea ice extent is reduced to about the levels we are currently seeing (i.e. about 4.5 M km2), suggesting that Arctic sea ice may be near a 'tipping point". Wang and Overland investigate future sea ice decline using only that subset of six global climate models that, in their estimation, best simulate current conditions. Projections based on two emission scenarios (SRES A1B and A2) were used to estimate the time required for sea ice extent to reduce to 1.0M km2 using the past two years of ice cover as a starting point. (1.0M km2 is representative of a nearly ice free ocean allowing that some ice will remain in the regions north of Greenland/Canada.) They find that the expected time frame to reach a virtually ice free Arctic in September is about 30 years, with little difference in the trajectories of sea ice decline for the two emission scenarios. Natural variability is still expected, however, to play a strong role in the future timing of a September sea ice free Arctic.
Wilbanks, T.J. and J. Sathaye. 2007. Mitigation and Adaptation Strategies for Global Change 12: 957-962.
Integrating mitigation and adaptation into a single portfolio of climate change response options is now well recognized. Preliminary findings about the nature of such portfolios include the need to emphasize options that offer synergies, recognition of the potential for unintended indirect consequences, and consideration of capacities for implementation.
A special issue of the journal Mitigation and Adaptation Strategies for Global Change (volume 17) is focused on the practical reality of integrating mitigation and adaptation in climate change response policy. A summary paper by Wilbanks and Sathaye takes the findings of the 16 peer-reviewed articles and draws some preliminary findings about appropriate mitigation and adaptation portfolios. First it is important to differentiate between options that offer complementarities and synergies (e.g., tree planting and other biomass sink preservation/conservation as examples of adaptation options that also reduce emissions) rather than those that have secondary climate change impacts (e.g., if climate change stimulates disease vector transmission, a response might be to add filters and space conditioning to protect against those vectors, which could require more energy). Several articles point to the opportunity of integrating sustainable development pathways into this portfolio of mitigation and adaptation options. Finally, the need to consider not just the what to do but also the capacity for implementation is considered, an area that is made more difficult by the varying geographic scales of these options - mitigation policies are often discussed and implemented at a global or national scale whereas adaptation is more relevant and necessary at a local scale. This series of papers advances the discussion of the integrating of mitigation and adaptation options from a theoretical discussion to a practical one.
Wright, R.F. et al., 2006. Modelling the effect of climate change on recovery of acidified freshwaters: Relative sensitivity of individual processes in the MAGIC model. Science of the Total Environment 365(1-3): 154-166
While acidified ecosystems in Europe and North America are predicted to recover based on decades of legislated cuts to SO2 and NOx emissions, most characterizations of this process have neglected to take climatic factors into account in modelling acidified ecosystem dynamics. Based on studies which have shown links between climatic factors and surface water trends, the authors present the results of a modeling exercise aimed at determining which climate-related model parameters are most relevant to ecosystem recovery. For fourteen sites in multiple countries (including Plastic Lake in Central Ontario), the authors systematically vary 8 climate-linked inputs into the MAGIC surface water acidification model. No attempt is made to model a coherent climate scenario; instead, the parameters are altered one-by-one to determine which are the most significant determinants of acid neutralizing capacity (ANC), nitrate concentrations and percent base saturation (%BS). The authors determine that none of the 8 inputs had any significant effect on NO3 concentrations (one of the three indicators examined), and that changing pCO2 (amount of carbon dioxide in soil) had almost no effect at any site on any indicator. ANC and %BS values at coastal sites were affected by seasalt concentrations, and deposition of Saharan dust was not significant to sites in Southern Europe (where its effect had been hypothesized). The most significant change in ANC (increase) and %BS (decrease) was observed with alterations in dissolved organic acid levels in soil solution. This is thought to be due primarily to leaching of base cations. One additional highlight was the tendency of increased decomposition of organic matter to increase NO3 concentrations. The authors state that downscaled GCM outputs are required for actual realistic predictions of future impacts of climate change on recovery of acidified ecosystems.
Xiao, J. and Q. Zhuang (2007), Drought effects on large fire activity in Canadian and Alaskan forests, Environ. Res. Lett., Vol 2, No. 4, 6 pages.
A new study demonstrates that drought significantly affected forest fire activity across Canada and Alaska over the past five decades. Future fire regimes in Canada and Alaska will likely depend on how drought patterns in this region change under global climate change scenarios.
Previous studies have shown that forest fire activity in Canada and Alaska, including fire occurrence and area burned, increased during the last four decades of the 20th century and that the area burned is linked to warming trends, and a combination of other factors that includes climate, lightning strike frequency, topography and forest cover. In a recent study, Xiao and Zhuang went a step further to understand the factors that contribute to fire activity in these regions. They used the Palmer Drought Severity index (PDSI) and historical large fire databases from 1959 to 1999 to examine the relationship between moisture conditions and fire activity across Canada and Alaska, focusing on large fires since if they represent only about 3% of the total number of fire (in Canada), they account for 97% of the total area burned. They also conducted spatial analyses of fires, droughts, temperature and precipitation for a number of large fire years and small fire years. Their results show, as in previous studies, that the annual area burned in Canada and Alaska exhibited a strong upward trend over the period 1959-1999, and that the number of fire events significantly increased. During the same period, they found that the percentage area experiencing drought over these regions exhibited a striking upward trend. They also found that the effects of temperature and precipitation vary spatially and temporally and that the concurrence of high temperature and low precipitation, or their separate effects, could all lead to drought and, thereby influence fire occurrence. They conclude that future fire regimes in forested regions over Canada and Alaska will likely depend on drought patterns under global climate change scenarios.
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