In the first major paper of its kind, a new study in the February 17 Nature has found that heavy precipitation is at least partly due to the growing concentration of manmade greenhouse gas emissions in the atmosphere. A team of scientists from Canada and Scotland used powerful computers to analyze the causes behind the rise in storms and heavy snowfall over the past half century. They found that the likelihood of extreme precipitation on any given day rose by 7% between 1951 and 1999—the years covered by the study. That's outside the bounds of normal variability, and the increase only make sense if rising greenhouse gas emissions and climate change are taken into effect. "Human influence on the climate system has the effect of intensifying precipitation extremes," said Francis Zwiers, a climate researcher at Environment Canada in Toronto and the study's lead researcher.
That conclusion shouldn't be that surprising—climatologists have predicted an uptick in extreme weather events as greenhouse gas concentrations in the atmosphere increase. Since warmer air can carry more water vapor, a warmer planet should see heavier rain and other precepitation—and that's what we've begun to see with actual weather. As an accompanying article to the Nature studies points out, for every 1 C in warming near the Earth's surface, scientists expect a 2-3% increase in total global precipitation.
But it's not global precipitation patterns that should really worry us—it's local rainfall, either too much or too little. We need scientists to be able to tell us whether a certain flood or a certain drought actually can be tied to global warming. And in another study published in Nature this week, that's exactly what a team of climatologists set out to do. With help from computer time donated by the public, the researchers analyzed the severe rains that flooded England and Wales in 2000, leading to some of the worst flooding in British history. They looked at the climate as it actually existed at the time, and then compared it to hypothetical climates as they would have been if human beings had never begun adding greenhouse gases into the atmosphere. The researchers concluded that the chances of such a major flood happening at that time were roughly doubled by the rise in greenhouse gases. "Greenhouse gas emissions due to human activity have affected the odds of floods in England and Wales," said physicist Pardeep Pall of the Swiss Federal Institute of Technology (ETH Zurich), who led the Nature research.
Given the billions of dollars for climate adaptation at stake, it's vital for scientists to deliver more rapid and accurate analysis of extreme weather events—like climate change CSI. But we're not there yet—the Nature study of the 2000 floods took a decade of work and incredibly complex computer simulations. But we'll need better analysis not just to predict coming extreme weather events and prepare for them—something that could have averted much of the damage from the terrible floods in Pakistan last summer—but in assigning cause and blame. That will matter for the business world—insurance companies will want to know just what caused devastating floods or storms as they pay out their claims. But it will also impact international climate negotiations. If developing countries—already on the front lines of global warming—can prove that carbon emissions from rich countries are causing what we once referred to as natural catastrophes, they may well be justified in demanding the equivalent of carbon reparations.
http://ecocentric.blogs.time.com/2011/02/17/new-studies-show-that-climate-change...So the science mounts ... when will the hard right embrace science and back Greens policies like a 40% cut in CO2 pollution. If they don't it's enough evidence to call the Liberals and the National Party's financially reckless.
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Climate Change Is the Culprit in Extreme Rain (Read 36589 times)
