In a shift, some climate scientists link extreme weather to global warming – ‘We’ve juiced the world’s climate system’

By Monte Morin, Los Angeles Times
12 October 2012 The worst drought in half a century has plagued two-thirds of the nation, devastating farms and stoking wildfires that scorched almost 9 million acres this year. Withering heat blanketed the East Coast and Midwest, killing scores of people and making July the hottest month ever recorded in the U.S. And in the Arctic this summer, polar snow and ice melted away to the smallest size ever observed by man. Extreme events like drought, heat waves, intense rainfall, flooding, and fires have prompted many people to reconsider the connection between the weather and the changing climate. Now, a handful of scientists are among them. In a break with the mainstream scientific consensus, a few prominent climate scientists now argue that there have been enough episodes of drought and intense heat in the last 10 years to establish a statistical pattern of extreme weather due to global warming. One of those scientists is NASA climatologist James Hansen. In a study published last month in the Proceedings of the National Academy of Sciences, he noted that dramatic events like droughts and heat waves affected just 1% of Earth’s surface between 1950 and 1980; in the last 30 years, that figure has jumped to 10%. “We can state, with a high degree of confidence, that extreme anomalies … were a consequence of global warming because their likelihood in the absence of global warming was exceedingly small,” he and his colleagues wrote. Hansen isn’t the only one who suspects that the signature of climate change can be seen in recent weather trends. Around the world, “the incidence of drought is consistent with what the climate models are predicting,” said John Seinfeld, an atmospheric researcher at Caltech. “It certainly doesn’t appear to be out of line to conclude that this last summer could be statistically attributed to global warming.” In the U.S., the summer ranked as the third-hottest in the nation’s history. Among laypeople, the perception that extreme weather is getting worse — and that it’s linked to climate change — is increasingly taking hold. Nearly 75% of Americans now say global warming is affecting the weather in the U.S., according to a poll released this week by scientists at Yale University. The poll found that about 60% of Americans reported experiencing an extreme heat wave or drought this year, while an equal percentage said weather had worsened over the last several years. A companion poll reported earlier this year that 8 in 10 Americans had personally experienced at least one extreme weather event in the last year, and more than one-third said they had suffered as a result. Jerry Lubell narrowly missed being one of them this summer, as a 100-foot wall of flames approached his Colorado Springs, Colo., home. The fire spared his house but left him shaken. “It has me thinking,” said the retired nuclear engineer, a longtime skeptic of the idea that human activity is behind global warming. “I haven’t changed any fundamental opinions yet, but I might.” Climate scientists overwhelmingly agree that the planet is getting hotter and that mankind’s use of fossil fuels is largely responsible. When fossil fuels are burned, carbon dioxide is produced and traps heat within the atmosphere. The more that’s added, the hotter it gets. It’s not the only greenhouse gas, but it’s the one many scientists focus on because it stays in the atmosphere for hundreds or thousands of years. The average global temperature has risen by 1.6 degrees Fahrenheit over the last century, a period that gave rise to mass-produced automobiles and commercial aviation, among other developments. Altogether, modernization has led to an 800% increase in global fossil fuel consumption since 1900, with a corresponding jump in emissions of heat-trapping greenhouse gases. As the temperature rises, evaporation increases and draws more water from soil. Experts predict that moist areas of the planet will become wetter, while dry areas will become drier. […] Asking whether the summer’s record heat was evidence of global warming is like asking whether steroids helped a baseball player hit a home run in the bottom of the ninth inning during the World Series, said Anthony Leiserowitz, an environmental scientist with the Yale Project on Climate Change. If the player was able to hit home runs before he took steroids, it would be impossible to know whether any particular home run could be traced directly to performance-enhancing drugs. However, at the end of the season, it would be clear that the player hit home runs with greater frequency. “That’s what we have here,” Leiserowitz said. “We’ve juiced the world’s climate system by putting these gases in the atmosphere.” […]

Some climate scientists, in a shift, link weather to global warming