Climate data and scenarios: synthesis of recent observation and modelling results, chapter 3.1


3.1 Temperature scenarios

In the following sections, multi-model climate change projections (relative to the 1986-2005 reference period) are shown for Canada. The format of the figures presented here is as consistent as possible with the analogous figures in the IPCC AR5 Atlas (IPCC, 2013--Annex I), referred to earlier, so as to allow direct comparison.

Time series of temperature anomalies, averaged over Canada covering the historical period (as simulated by the CMIP5 models) and the future (to year 2100), are shown in Figure 5. Results for three future forcing scenarios, RCP2.6, RCP4.5, and RCP8.5 are provided. The individual thin lines are the results of the individual models listed in Table 2 and the heavy line represents the multi-model ensemble average. Temperature anomaly is defined as the temperature relative to the 1986-2005 reference period. The range of values, quantified by the box and whisker plots to the right of each panel, results from both natural climate variability (as simulated by the models) and the differences in the detailed representation of physical processes in each model. As can be seen by comparing these plots to the global mean plots in the IPCC Atlas (IPCC, 2013-Annex I, pp. 1318-1319), the historical and projected changes for Canada are considerably larger (roughly 50 %) than for the global land area.
Figure 5

Figure 5 - Time series of historical and projected temperature change for the December, January, and February (left) and the June, July, and August (right) averages, as simulated by the CMIP5 multi-model ensemble. As in Annex I of the IPCC AR5 (IPCC, 2013), the individual curves represent the simulation results for individual models, while the heavy lines indicate the ensemble average. Results are shown for Canadian land areas only. Change is computed relative to the 1986-2005 period. The spread amongst models, evident in the thin curves, is quantified by the box and whisker plots to the right of each panel. They show, for the 2081-2100 period, the 5th, 25th, 50th (median), 75th, and 95th percentile values.

Long description of Figure 5

This figure has two graphs. The left graph represents a time series of historic and projected temperature change for winter (December, January, and February) as simulated by CMIP5 multi-model ensemble for grids covering Canada. A solid line represents the historic change from 1900 to 2005 and shows an increase from around -1.8°C to around 0°C. The RCP2.6 line then continues to increase until it reaches around 2°C in 2100. The RCP4.5 line continues on from 2005 to 2100 with an end point of around 4°C. The RCP8.5 projection shows a change of around 8.5°C by 2100. The right graph represents a time series of historic and projected temperature change for the summer (June, July, and August) as simulated by CMIP5 multi-model ensemble for grids covering Canada. A solid line represents the historic change from 1900 to 2005 and shows an increase from around -1°C to around 0°C. The RCP2.6 line then continues to increase until it reaches around 1.2°C by 2100. The RCP4.5 continues on from 2005 to 2100 with an end point of around 2.8°C. The RCP8.5 projection shows a change of around 6.3°C by 2100.

Even within Canada, climate change is not projected to be uniform, and so national average values may not be suitable for many applications. Figures 6 and 7 show maps of temperature change from the CMIP5 multi-model ensemble, based on the RCP4.5 scenario. Similar maps for the other RCP scenarios are available from the Canadian Climate Data and Scenarios website. RCP4.5 is used here for illustration purposes (as in the IPCC Atlas) and its use here does not imply that it is more probable than the other RCPs.

Figure 6

Figure 6 - Maps of winter temperature change projected by the CMIP5 multi-model ensemble for the RCP4.5 scenario, averaged over December-February. Change is computed relative to the 1986-2005 baseline period. As in the IPCC Atlas (IPCC, 2013), the top row shows results for the period 2016-2035, the middle row for 2046-2065, and the bottom row for 2081-2100. For each row the left panel shows the 25th percentile of simulated temperature change (25% of individual simulations show warming less than this), the middle panel the 50th percentile (median), and the right panel the 75th percentile. The color scale indicates temperature change in °C with positive change (warming) indicated by yellow through red colors and cooling by blue colors, consistent with the color scale used in the IPCC AR5 Annex I (IPCC, 2013).

Long description of Figure 6

This figure consists of 9 maps of Canada showing projected changes in temperature, driven by RCP4.5, for the winter (December, January, and February), organized in a 3 by 3 grid, with the 25th (left column), 50th (middle column) and 75th (right column) percentiles across the top of each column and the years 2016-2035 (first row), 2046-2065 (second row), and 2081-2100 (third row) down the side to indicate the years for each row. Each map shows an increase in temperature across the country, with the greatest warming in the north and over Hudson Bay. As the percentiles go up, the warming represented in the maps increases. The same is true for time, as the projection goes further into the future, the represented temperature increases, so the map in the top left (25th percentile for 2016-2035), shows the least amount of warming, whereas the bottom right map (75th percentile for 2081-2100), shows the greatest warming.

Figure 7

Figure 7 - Maps of summer temperature change projected by the CMIP5 multi-model ensemble for the RCP4.5 scenario, averaged over June-August. Change is computed relative to the 1986-2005 baseline period. As in the IPCC Atlas (IPCC, 2013), the top row shows results for the period 2016-2035, the middle row for 2046-2065, and the bottom row for 2081-2100. For each row the left panel shows the 25th percentile, the middle panel the 50th percentile (median), and the right panel the 75th percentile. The color scale indicates temperature change in °C with positive change (warming) indicated by yellow through red colors and cooling by blue colors, consistent with the color scale used in the IPCC AR5 Annex I (IPCC, 2013).

Long description of Figure 7

This figure consists of 9 maps of Canada showing projected changes in temperature, driven by RCP4.5, for the summer (June July, and August), organized in a 3 by 3 grid, with the 25th (left column), 50th (middle column) and 75th (right column) percentiles across the top of each column and the years 2016-2035 (first row), 2046-2065 (second row), and 2081-2100 (third row) down the side to indicate the years for each row. Each map shows an increase in temperature across the country, with the greatest warming in the south, and the least over the arctic. As the percentiles go up, the warming represented in the maps increases. The same is true for time, the further into the future the projection represents, the temperature change increases, so the map in the top left (25th percentile for 2016-2035), shows the least amount of warming, whereas the bottom right map (75th percentile for 2081-2100), shows the greatest warming.

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