Last week a severe storm froze Dallas under a sheet of ice, just in time to disrupt the plans of the tens of thousands of (American) football fans descending on the city for the Super Bowl. On the other side of the globe, Cyclone Yasi slammed northeastern Australia, destroying homes and crops and displacing hundreds of thousands of people.
Some climate alarmists would have us believe that these storms are yet another baleful consequence of man-made CO2 emissions. In addition to the latest weather events, they also point to recent cyclones in Burma, last winter’s fatal chills in Nepal and Bangladesh, December’s blizzards in Britain, and every other drought, typhoon and unseasonable heat wave around the world.
But is it true? To answer that question, you need to understand whether recent weather trends are extreme by historical standards. The Twentieth Century Reanalysis Project is the latest attempt to find out, using super-computers to generate a dataset of global atmospheric circulation from 1871 to the present.
As it happens, the project’s initial findings, published last month, show no evidence of an intensifying weather trend. “In the climate models, the extremes get more extreme as we move into a doubled CO2 world in 100 years,” atmospheric scientist Gilbert Compo, one of the researchers on the project, tells me from his office at the University of Colorado, Boulder. “So we were surprised that none of the three major indices of climate variability that we used show a trend of increased circulation going back to 1871.”
In other words, researchers have yet to find evidence of more-extreme weather patterns over the period, contrary to what the models predict. “There’s no data-driven answer yet to the question of how human activity has affected extreme weather,” adds Roger Pielke Jr., another University of Colorado climate researcher.
We do know that carbon dioxide and other gases trap and re-radiate heat. We also know that humans have emitted ever-more of these gases since the Industrial Revolution. What we don’t know is exactly how sensitive the climate is to increases in these gases versus other possible factors—solar variability, oceanic currents, Pacific heating and cooling cycles, planets’ gravitational and magnetic oscillations, and so on.
Read more here.