When Hurricane Katrina ravaged New Orleans in 2005, it was the most graphic evidence many Americans had seen so far of what scientists had been saying for years: as carbon emissions from the burning of fossil fuels build up in the atmosphere, more and more heat energy will be trapped near the Earth’s surface, increasing the odds of catastrophic weather events. Though the debate continues as to whether or not conditions that led to Hurricane Katrina were actually caused be climate change, most scientists agree that intense, life-threatening storms will become more common as climate change continues.
Now, in the fallout from the second worst US weather disaster in recent years, it’s worth asking whether climate change had a part to play. Did warmer conditions in the planetary atmosphere and changed local weather patterns contribute to damage caused by tornadoes in the South last week?
The answer isn’t entirely obvious. Some scientists have hastened to point out that no solid link can be drawn between climate change and this particular batch of tornadoes. But what’s clear is the group of storms that hit Alabama and surrounding states were caused by an unusual set of weather conditions. Moist, warm air rose high into the atmosphere where it combined with drier, colder air currents to create the conditions that lead to tornado formation. This happened in just the right time and place for the jet stream—a permanent wind that stretches across the North American continent—to nudge pockets of reactive air into the spiraling motion needed to produce tornadoes.
As a result, at least a hundred individual tornadoes descended on Alabama, Mississippi, Arkansas, Tennessee, Georgia, Louisiana, and Virginia. At least 310 people were killed, and the storms caused billions of dollars in property damage. It’s the worst tornado outbreak since 1974 and the worst weather-related disaster in the US since Hurricane Katrina. The tornado swarm also seems to be part of a much larger rash of recent extreme weather events around the world, from runaway forest fires in Russia last summer to massive floods that hit Australia in December.
No single one of these weather events can be traced to climate change with 100% certainty. In fact, because of the mixture of local conditions that lead to storms, droughts, and flooding, it’s unlikely scientists will ever be able to “prove” a link between extreme weather and human activity. But a NASA study in 2007 predicted climate change would lead to more tornadoes and lethal storms in the United States, and ignoring this warning in light of recent events would seem foolhardy. Whether or not last week’s tornadoes were caused by climate change, extreme weather is on the rise.
When you look at a single storm or drought, it’s always possible to find factors besides climate change that might be responsible for what seems like an unusual event. For instance, meteorologists say what appears to be an uptick in US tornado activity could simply be due to improved methods for tracking and recording storms. But last week’s tornado outburst wasn’t something that could have been missed without modern storm-tracking technology. It was an extremely unusual and deadly weather event, and the worst US tornado incident in more than a quarter century. Similarly, Russia’s forest fires last summer were worse than any seen in that country for many decades, if ever. Floods in countries from Australia to Pakistan to Brazil have broken records and caused irreparable damage throughout the past year. Any one of these events might be traced to factors besides climate change. But the overall increase in destructive weather seems undeniable.
When it comes to extreme weather, it might be wise to apply the precautionary principle, which states that when substantial evidence exists for a link between a certain policy and danger to human life, absolute proof shouldn’t be needed to prompt a change in policy direction. Today, the US policy of burning fossil fuels unabated has increased the probability of life-threatening storms. By the time the link between climate change and any one weather event can be absolutely established, it may be too late to do anything—as horrifically demonstrated in the South last week.
Photo credit: flickr.com/photos/69149038@N00/1147034479/sizes/m/in/photostream/