This year is on track to enter the almanac as one of the three warmest years on record globally, along with 1998 and 2005, according to a preliminary analysis by the World Meteorological Organization.
Not only that, but 2010 stands a decent chance of capturing the record, depending on temperature data from November and December, according to Michel Jarraud, secretary-general of the WMO. Global average temperatures for the first 10 months of the year are running slightly ahead of those for the same period in '98 and '05, he noted during a press briefing Thursday at UN-sponsored climate talks under way in Cancun, Mexico.
Preliminary temperature data for November are comparable to temperatures seen in November 2005, indicating they have remained near record levels as the year winds down.
Even if 2010 fails to capture the top spot, the first decade of the 21st century already has gone into the books as the warmest since 1850, when the instrument record began.
The data are part of the WMO's annual roundup of global weather activity, especially extreme events such as floods, heat waves, deep cold snaps, and severe storms.
Some climate scientists caution that any one year's worth of events is driven more by natural variability than by long-term warming triggered by the released of carbon dioxide from burning fossils fuel. But when 2010's extreme events are seen in that broader context, they appear to fit long-term patterns the climate models have generally projected for a climate system responding to increasing atmospheric concentrations of greenhouse gases.
A range of studies have documented an increase in extreme heat events, a decrease in extreme cold events, and an increase in rainfall and snowfall intensity globally during the past 50 years, atmospheric scientist Gerald Meehl, with the National Center for Atmospheric Research in Boulder, told the House Energy and Environment subcommittee last month.
On the basis of physical principles alone, "we could expect to see just these kinds of changes in extremes in a warming climate," he testified.
In the US alone, he noted, the past decade saw high temperature records being set twice as often as low-temperature records, whereas in a climate without the additional greenhouse gases humans have pumped into the atmosphere, the ratio would average over the long term about 1 to 1. So far in 2010, the ratio was closer to 3 to 1, he said. Meanwhile, precipitation intensity has increased over the past 50 years, traced to the additional moisture the atmosphere can hold when it warms.
Some of the events in 2010 the WMO found noteworthy:
• Unusually heavy monsoons in Pakistan that brought the worst flooding in that country's history. The floods forced 20 million people to leave their homes and covered a significant portion of the country's farmland. At least 1,500 people were killed in the flooding, according to international relief groups.
• A record-smashing heat wave in Russia last summer. Moscow posted its highest temperature on record, at just over 100 degrees Fahrenheit, and recorded 33 consecutive days during which temperatures topped 86 degrees F. Both the heat wave and Pakistan floods resulted from the same large-scale weather pattern that stalled over that part of the globe, Dr. Jarraud notes.
• An unusual northern-hemisphere winter in which Canada posted its warmest and driest winter on record – some 7 degrees F above the long-term average –while the US recorded its coldest winter in 25 years, with storms dumping heavy snows across much of the continent, including a season record snowfall for Washington, D.C. Central Russia also experienced a colder-than-normal winter, although not outside historical experience. Likewise for much of Europe. But Canada's unusual warmth also extended east across Greenland and the Arctic above Scandinavia, offsetting the chill at lower latitudes. A large portion of Asia, as well as North Africa and northern Brazil, also experienced above-normal temperatures for the December-to-February period.
The winter weather in the US and Europe prompted some people in those areas to question whether global warming had taken a break. Noting people's tendency to gauge global climate change by checking their local weather, Jarraud cautioned, "don't focus only on one place to draw a general conclusion; you have to look at the global picture."
The WMO built its interim report for 2010 from data gathered by the National Oceanic and Atmospheric Administration, NASA, and data from Britain's Hadley Center and the Climate Research Unit at the University of East Anglia. The latter was ground zero for a controversy last year triggered by an unauthorized release of e-mails that spotlighted a seamier side to scientific behavior. Subsequent investigations found no evidence that scientific results were tainted by practices and attitudes the e-mails portrayed.
Still, the WMO this year has used data from a fourth institute, the European Center for Medium-Range Forecasting, as a reality check on the other three, as well as for preliminary data for November.
The WMO plans to provide a final report on 2010's weather patterns and how they compare with long-term climate "normals" next February.