Crossposted with TheGreenGrok.
The American public may have it right this time.
Weather is fundamentally strange -- as we go from one season to the next, it's hard to know what to expect. Long-range weather forecasts can help a bit, but it's still a crapshoot when trying to suss out, for example, whether we're headed for a hot or mild summer this year. Even so, we seem to have been subjected to especially bizarre and extreme weather over the past two to three years. Examples include:
- The historic drought and record-breaking heat (and resulting wildfires) that began in 2010 across Texas and the Southwest.
Are these recent events just a bump in the road of weather variability or part of a long-term trend? Are they simply part of the natural variability of our climate or one of many manifestations of global warming?
These are difficult questions to answer. The first question is challenging because weather is so variable and that variability makes it difficult to tease out a long-term trend from all the noise of natural variations.
Nevertheless, scientists love a challenge and have been trying to answer these questions. A growing number of studies do in fact indicate that some aspects of the weather have been increasing in intensity over the past few decades.
For example, a 2010 study of trends in European rainfall events between 1950 and 2008 found that there has been a shift toward longer events and that the tendency with the longer events has been for more intense rainfall. A study from last year found that Northern Hemisphere precipitation in general is becoming more intense. Studies examining heat and drought have found that dry periods are increasing in number and getting longer and that extreme summer temperatures are occurring more often in the United States.
(In a related work just published in the journal Science, Paul Durack of the Lawrence Livermore National Laboratory and colleagues report that trends in the salinity of surface ocean water point to a decadal intensification of the water cycle such that wet places are becoming wetter and dry places are becoming drier.)
The second question is even more difficult to answer: the climate is a measure of the long-term average state of the atmosphere, and so it is virtually impossible to attribute any single weather event, no matter how extreme, to climate change. Nevertheless, inferences can be made, for example, using probabilistic arguments. And for the most part these approaches do in fact indicate that global warming could very well be a significant contributor to many of these events. But note all the caveats: "could... be," "significant," "many." We just can't do better than that.
Even so, a Yale-George Mason poll suggests that a significant number of Americans are pretty well convinced.
John Q. Public Weighs In
Scientists have been known to lament over the fact that the American
public just does not seem to understand what's going on with the
climate. While virtually all of the major scientific associations
including the U.S. National Academy of Sciences, have concluded that
global warming is real, is largely caused by human activities, and is a
serious enough problem deserving of concerted action to mitigate, a
significant percentage of Americans remain unconvinced or unconcerned.
But the recent Yale-George Mason poll suggests the tide may be turning: "three out of four U.S. voters favor regulating carbon dioxide as a greenhouse-gas pollutant," as Reuters reported on the survey. And in the case of extreme weather, it appears that the American public may be out in front of the scientists. According to the poll,
- By a margin of more than two to one (52 percent versus 22 percent), Americans say the weather in the United States has been getting worse, not better.
- About half of all Americans (43-53 percent) say that heavy rains and heat waves and droughts have become more common in their local area over the past few decades.
- A large majority of Americans (59-72 percent) believes that global warming made recent high-profile extreme weather events worse.
So which do you find more bizarre? The apparent trend in weird weather or the swing in public opinion about climate change? And which do you think is more likely to hold?