In 2010, the evidence for global warming just keeps piling up
Wednesday, October 6, 2010
The first six months of the year were warmer than any previous January-June period on record. Add to that a new report confirming that global surface temperatures during the past decade between 2000 and 2009 were the warmest of the past century
by HENRY HENGEVELD
It looks like 2010 will become another year for the climate record books – locally, nationally and globally.
Take this summer, for example. By early August, there had already been 15 days with local day-time temperatures in the Greater Toronto Area soaring past 30 C. High humidity helped push the humidex into the mid-40s for a good number of those days. Humid nights with temperatures remaining well above 20 C – already eight such nights so far – made for uncomfortable sleeping conditions, at least for those of us without air conditioning.
Many Ontarians found this heat hard to take, and grumbled! Mind you, there are always those who fared far worse. In mid-summer, massive floods in Pakistan affected more than 13 million of its citizens. Heavy rains also caused massive landslides in China, killing hundreds.
Meanwhile, an intense heat wave throughout most of June and July, with daily temperatures hovering some 4 to 8 C above normal and at times exceeding 40 C, caused large scale droughts across Russia, while triggering massive forest fires and generating severe smog conditions around Moscow.
Reports from local hospitals indicated a large increase in admissions from respiratory, heart and heat-related ailments, and suggested that Muscovites were dying at double the normal rate. Crop analysts were also predicting significant losses in agricultural yields.
By comparison, a few restless nights and sweaty days are a relatively minor inconvenience.
However, what makes the warm summer in Ontario so unusual is that it followed directly on the heels of very unusual winter and spring seasons. In the Great Lakes region, spring temperatures averaged 3.8 C above and precipitation 33.5 per cent below normal, making this spring the warmest and second driest since national record keeping began 63 years ago.
The Great Lakes basin also experienced a winter season (December to February) that was the ninth warmest and fourth driest on record. Furthermore, long-range seasonal forecasts prepared by Environment Canada project that the warm weather over Ontario will continue into the coming fall months.
The rest of the country seems to have followed suit. Between December and May, temperatures across the nation have averaged about 4 C above the norm, making this the warmest Canadian winter and spring seasons on record. While the average precipitation across the country during the spring season was not abnormal, the winter season, with precipitation averaging 22 per cent below normal, was also the driest ever.
Global temperature analysts indicate that most regions of the world are also experiencing unusually warm conditions. Reports in early August concluded that the average global surface temperatures during the first six months of 2010 were warmer than any previous January-June period during the past 130 years of record keeping.
Barring the early onset of an intense La Niña during the remainder of the year, experts were predicting that 2010 would set new high temperature records.
Meanwhile, satellite data indicate that average Arctic sea ice extent for this past July was 1.71 million square kilometres below the 1979-2000 mean, almost reaching the record set in July 2007. The linear rate of decline of July ice extent over the period 1979 to 2010 is now 6.4 per cent per decade.
In mid-July of this year, the U.S. National Oceanic and Atmospheric Administration (NOAA) released a new report that helps put the unusual climate conditions of the first half of 2010 into context with respect to the global climate of the past century and beyond.
The large international team of scientists involved in the study came from 48 different countries. They collectively examined 10 different climate indicators, including surface air temperatures over global land masses and over oceans, sea surface temperatures, ocean heat content, temperature and humidity of the troposphere, the size of glaciers, the extent of snow cover over the Northern Hemisphere and of sea ice in the Arctic.
Each indicator involves independent data sets and analysis techniques, yet all indicators tell the same story. Temperatures are rising throughout the climate system, the heat stored in oceans is increasing, the troposphere is becoming moister, and glaciers, snow cover extent and Arctic sea ice cover are all retreating.
The report also confirms earlier reports that global surface temperatures during the past decade between 2000 and 2009 were the warmest of the past century, and that average temperatures have risen by 0.2 C during each of the past three decades. Furthermore, there is strong evidence that extreme weather events, particularly heat waves, severe droughts and disastrous floods, have also become more frequent.
That report concluded that global warming is now "undeniable." While other reports by well-respected scientific agencies have said as much in the past, NOAA's conclusion is supported by some of the most convincing evidence yet accumulated.
The unusual climate conditions during the first six months of 2010 appear to be piling on some more of this evidence.
Henry Hengeveld is Emeritus Associate, Science Assessment and Integration Branch/ACSD/MSC, Environment Canada.
