Warming Causes Weather Disasters

LONDON (AlertNet) – Scientists tackled the highly debated, and somewhat perplexing, relationship between climate change and weather disasters at the recent launch of a U.S. magazine series on the subject, concluding that an indisputable connection exists between the two.

“The link between climate change and extreme weather is not so much theoretical as observational,” Fred Guterl, executive editor of monthly magazine Scientific American, told reporters on a conference call late last month.

“It’s possible to look at this and really begin to see, in a way that you can measure, that this is not really just business as usual in terms of weather. There really is a climate signal.”

The three-part series in Scientific American by science journalist John Carey was funded by the Pew Center on Global Climate Change, which is based in Arlington, Virginia.

In conjunction, Pew Center experts Jay Gulledge and Dan Huber have released a report that attempts to demystify the impacts of climate change on global weather conditions, and were also on hand to discuss their findings.

Gulledge explained to journalists that much of the confusion surrounding global warming and extreme weather events – including floods, droughts and heat waves – stems from the public’s desire for definitive cause-and-effect answers and scientists’ unwillingness to provide them.

“The question, ‘Did climate change cause this event?’ is just a scientifically illogical question. It doesn’t comport with the definition of climate because that is an average over time,” he said.

Because the word “climate” refers to a mean value, one cannot draw a straight line between global warming and a certain hurricane, for instance, he explained.

The paper puts it like this: if the norm used to be one hurricane per year and then after global warming started, there were two hurricanes per year, scientists cannot determine which was caused by climate change because the two are indistinguishable. The effect of climate change is the increase in the average number of hurricanes.

“The upshot is that one event doesn’t actually have information about climate change and vice versa,” Gulledge said. “So it becomes this question that people focus on that science fundamentally has no answer for.”

But that does not mean extreme weather events in the recent past are not, at least partially, the product of global warming.

WEATHER EQUIVALENT OF SPEEDING

The Pew Center report refers to the barrage of weather disasters that plagued the world last year. 2010 tied with 2005 as the warmest year globally since 1880, with 19 countries reaching their highest temperatures ever, the largest number of new records in a single year.

Parts of Pakistan endured Asia’s hottest temperatures in history; Russia lost 56,000 people to an unprecedented heat wave; and China’s Yunan province saw its worst drought in 100 years. It was also the wettest year since 1990, bringing deadly floods to Pakistan, Brazil, Australia, and many areas of the United States.

Yet while climate change did not directly cause these events, it is responsible for their elevated frequency and heightened intensity, according to the report.

“Just as speeding increases the risk of a deadly auto accident, but cannot be conclusively assigned as the cause of an accident, a particular heat wave is not directly caused by global warming, but has a higher risk of occurrence and of being intense because of global warming,” the analysis states.

Floods and droughts occurred long before any human-induced changes to the surface temperature of the earth. But recent large-scale shifts – over the past 50 years, total rainfall has risen by 7 percent and temperatures continue to reach new highs – have made extreme weather events in general more common and more dangerous.

“What matters is that there is a statistical record of these events occurring with increasing frequency and/or intensity over time, that this trend is consistent with expectations from global warming, and that our understanding of climate physics indicates that this trend should continue into the future as the world continues to warm,” the report says.

Rather than trying to predict the details of specific catastrophic events, policymakers should collaborate with scientists to understand these evolving trends in weather patterns, which will undoubtedly play a role in future disasters as global warming continues, the researchers recommend.

“The signal of climate change is emerging from the noise of immense variability of weather,” Scientific American’s Carey said. “If you look at an individual event, it wasn’t caused by climate change, but the intensity, the size, whatever, was caused by climate change.”

Soumya Karlamangla is an AlertNet Climate intern.