Read more: “Climate change: It’s even worse than we thought“
In 2010, Russia sizzled as the temperature hit nearly 40 °C in several cities. In 2011, the “Groundhog Day blizzard” dumped astonishing amounts of snow across the eastern US and Canada. This year, too, has been , from summer deluges in the UK to a storm knocking out power to millions in the US – and of course, the devastation wrought by superstorm Sandy.
Such events fit a pattern. In a warming world, shifting rainfall and increased evaporation will lead to more droughts. A warmer atmosphere holds more water, making rainfall at times more intense.
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It is difficult, though not impossible, to say how individual events are influenced by climate change. It is simpler to tell whether the overall numbers are increasing. Even at the time of the last IPCC report in 2007, the trends for , and intense rainfall were already clearly upward.
Not only are these trends continuing, but the weather is also becoming even more extreme than was predicted. For instance, a study this year of ocean-salinity data from between 1950 and 2000 by the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO) found that the global water cycle – the rate at which water evaporates and falls as rain – has increased at . Work by researchers from Taiwan and China found that the increase in rainfall intensity over the past three decades has been . As for extraordinary heatwaves such as those in Europe in 2003 (see “Climate downgrade: Heat stress“) and 2010, .
Climate scientist of Rutgers University thinks warming in the Arctic (see “Climate downgrade: Arctic warming“) could be part of the explanation. As temperature differences between the north pole and the tropics fall, the polar jet stream, which pushes weather systems around, is meandering more and slowing down. This means weather patterns are more likely to get “stuck” in place. “Following the record-shattering loss of Arctic sea ice this summer, I would expect the jet stream to dish up a smorgasbord of extreme weather events all around the northern hemisphere,” says Francis. Such a blocking pattern , perhaps implicating Arctic ice loss.
Studies of past climate suggest future weather could get even wilder. Between 5 million and 3 million years ago, for instance, the world was 2 °C to 4 °C warmer than today. According to a study by and his colleagues, published in 2010, rising numbers of hurricanes altered the distribution of heat in the oceans and ultimately , with warmer tropics and far more hurricanes occurring over a much wider area than today. “I think it plausible that hurricane feedback could influence the way climate changes over the next few hundred years,” says Emanuel. “I only wish we understood the problem better.”
