Top ten weather stories for 2010: story four

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4. Canada’s a “Hottie”!

A map of Canada indicating the whole country as having warmer than average temperatures.

Sun overlooking a body of water.  © 2010

If you were to stick a thermometer into Canada at any time this year, it was sure to say “well done”. That the year began with the mildest winter on record was remarkable in its own right. But what followed was truly phenomenal – we had the warmest spring, the third warmest summer and the second warmest fall on record, making 2010 the warmest year in 63 years.

Temperatures for the 12-month period spanning December 2009 to November 2010 averaged 2.9°C warmer than normal and almost a half degree higher than the previous warmest years (2006 and 1998). It was also the 14th consecutive year with above-normal temperatures. The story was similar across the country. Every region was warmer than normal, with the Arctic, Atlantic Canada and the eastern Canadian boreal forest being the warmest on record and the Great Lakes/St. Lawrence, northern British Columbia and Yukon being the second warmest. This year’s El Niño accounted for much of the warmth in 2010, but La Niña’s emergence before August didn’t seem to subtract from the year’s record warmth.

Winter 2009-2010 was the warmest in Canada since nationwide records began in 1948, logging in at 4.0°C above normal. The national average temperature for spring 2010 was 4.1°C above normal, which was the greatest temperature departure of any season in 63 years of records. The season’s temperature records were shattered across the Canadian North, with some more than 6.0°C higher in certain Arctic areas. Summer was also warm, with the national average 1.3°C above normal, making it the third warmest on record. As the year-end approached, weather data showed that the average temperature from January 1 to November 31 was 2.9°C warmer than normal – the warmest first 11 months on record. Several places registered their warmest year on record in 2010.  Most noteworthy were several weather stations in the North.  For example, at Iqaluit, the average daily temperature was -4.2ºC, almost 5 degrees warmer than normal and 2.4 degrees warmer than the previous record in 2006.  Credit a couple of factors for the warmth in 2010, including a moderate to strong El Niño (a warm Pacific current that lingered for the first few months), less ice in the Arctic and, likely, climate change.

There is no question that the Canadian climate is changing, as all seasons have shown a warming trend since 1948. Change in the Canadian Arctic is the most pronounced as it could eventually leave the Arctic ice-free in the summer months. That’s not likely just a result of warmer Arctic temperatures. It’s not inconceivable that unusual and extreme weather occurring anywhere in the Northern Hemisphere might be linked to the vanishing of ice at the top of the world. Polar ice is one of the major forces that controls and drives climate across the world.

With consistently warmer temperatures, it is becoming increasingly more difficult to grow sea ice in the Arctic Ocean. With one of the warmest fall-winter-springs on record, sea ice never grew thick, hard and far. For example, in January, sea ice grew an average 34,000 square km a day, which is slightly more than one-third the pace of ice growth during the 1980s. Further, with more storms (in part because of more open water), ice now forms less readily. Also of note, new-year ice in the North is increasingly thinner. Multi-year ice – the thick, hard stuff that stops ships – now comprises only 18 per cent of the Arctic ice pack; 30 years ago it was 90 per cent.

According to Environment Canada’s Canadian Ice Service, sea ice in northern Canadian waters started to melt in the spring two to three weeks earlier than normal. The melt continued through the summer, resulting in a record low total ice concentration, with records dating back to 1971. Total accumulated ice in the summer covered about 33 per cent of northern Canadian waters – about 7 per cent less than that of the previous record in 1998 and about 28 per cent less than that of the long-term average from 1971-2000. On September 10, the low point of the ice season in terms of coverage, the ice extent was almost half that of the long-term average (748,100 square km vs. 1,544,800 square km).

For the Arctic Ocean, data from the United States National Snow and Ice Data Center indicated that ice cover was retreating fast in May, an average of 68,000 square km a day and more than in any previous May since satellite monitoring began over 30 years ago. However, 2010 did not produce a record meltdown in the Arctic Ocean. Still, by mid-September, minimum Arctic sea ice levels had reached 4.76 million square km – their third-lowest ice extent in the last 30 years and close to the stunning retreat that occurred in 2007 when ice shrank to 4.28 million square km. Also noteworthy: the minimum ice extent in 2010 occurred on September 19, which was eight days later than average; sea ice volume plunged to a new record low in 2010 according to the University of Washington’s Polar Science Centre; and, for the first time, both Canada’s Northwest Passage and Russia’s Northeast Passage were ice-free at the same time.

Looking back at the year, a warmer Canada is in step with what is happening across the world as reported by the UN’s World Meteorological Organization. Globally, 2010 was the 32nd consecutive year with above-normal temperatures and was also in the top three of the warmest years since observations began 160 years ago. The ten warmest years globally have all occurred since 1990; the top three since 1998. Further, 2001-2010 was the warmest ever for a ten-year period.

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