As the war over warming perception spills into a new decade, the last month of 2009 provided fresh ammo for the prevailing view. According to a preliminary report from the World Meteorological Organization (WMO), the “noughties” may have been the warmest decade on record.
And despite the rare sprinkling of snow we woke up to one December morning in the Bay Area, the report also says that 2009 will likely go down as one of the hottest years in modern history. Based on climate data from January to October, the WMO says that 2009 will likely be the fifth warmest since scientists began keeping records in 1850.
If that last claim seems improbable, you’re likely in Canada or the United States: The data shows that every continent but North America saw above-average temperatures in 2009, and that parts of Asia and Africa experienced their warmest year yet.
Dean Moosavi, a professor at the University of Massachusetts, Dartmouth, chalked the apparent discrepancy up to the Pacific ocean phase known as La Nina, and said it’s important to note the difference between weather and climate. “Snow in Houston this week, for example, is not proof of the absence of global warming any more than a large drought in the summer is proof that global warming is occurring,” Moosavi wrote in an email to Climate Watch. “You have to look over much longer periods of time…decades at the least before you can see a climatic trend of significance.”
This is perhaps a good place to acknowledge the oft-heard claim that the planet has actually been cooling down for more than a decade. In an article published in NOAA’s online magazine ClimateWatch (not affiliated with KQED Climate Watch), David Easterling of NOAA’s Climatic Data Center explains the statistical quirk that produces that mirage.
But Moosavi says he’s not quite ready to make a pronouncement. “I am not yet convinced that the 2000′s were warmer than the 90′s at this point,” Mossavi wrote. “Given the political and economic stakes of a statement of this type…I would be very cautious before declaring the 2000′s the warmest decade.”
Stanford’s Mark Jacobson, on the other hand, was less equivocal: “As 8 of the 10 warmest years in the history of surface measurements are in the 2000′s, it is clear that the 2000s was the warmest decade on record,” he wrote in an email.
The WMO findings come on the heels of a pair of reports that indicate that despite the global recession, average temperatures are on track to rise between 4 and 6 degrees Celsius by the end of the century.
For some perspective, the California Climate Change Center’s 2006 report on the risks of global warming predicts that a 6 C increase would have a devastating effect on the state. The report projects that a 10.5 F increase (just a little under 6 C) would result in up to 100 extra days of “extreme heat” in Los Angles and Sacramento, a 90% reduction in the Sierra snowpack and a 2-to-3-foot increase in sea levels.
The half-dozen climate scientists contacted for this post agreed that the 6 C prediction was within the realm of possibility, and most had the same answer when asked how the world should combat this risk. Stanford professor Ken Caldeira chose to respond in capital letters: “WE HAVE TO ACT NOW.”
“The question isn’t so much whether we need to take action this year or next, but rather how much more expensive and difficult are the solution and the impacts, if we delay,” Chris Field, director of the Carnegie Institution’s Department of Global Ecology, said. “Delaying action on climate is sort of like delaying action on paying your credit card bill. You may get by for a few months, but the problems get worse through time and more expensive to address.”