07 November 2012

Did climate change contribute to Sandy? Yes

Dr Bob Corell, Dr Jeff Masters and Dr Kevin Trenberth, Politico, November 5, 2012

As Hurricane Sandy battered the East Coast this week, meteorologists and climate scientists were repeatedly asked to explain what role climate change played in amplifying the storm.
     We did our best to answer: We know that a warming climate puts more energy into storms, including hurricanes, loading them with more rainfall and the stronger winds pushing more of a storm surge. That makes flooding more likely. We also know that storm surge now rides higher on sea levels that have risen over the last century due to global warming, amplifying losses where the surge strikes. On the stretch of the Atlantic Coast that spans from Norfolk to Boston, sea levels have been rising four times faster than the global average.
     Overall, we know that climate change has stacked the deck so that this kind of event happens more frequently. That answer, however, prompts a deeper, more unsettling question that many want to know: is climate change worsening some recent extreme weather events like super storm Sandy?
     The short answer is yes. Climate scientists broadly agree that the extreme weather we’ve seen over the past few years is exactly what we’d expect to see in a changing climate. And it’s not just Sandy; we’re on track to have the hottest year in more than a century of record-keeping in the continental United States, the country has suffered one of the most crippling droughts in history, as well as one of the worst wildfire years in history. Last year, when Hurricane Irene hit the United States, meteorologists called it “unprecedented,” yet Sandy has already outpaced the damage from Irene.
     We’ll probably never know the exact point when the weather stopped being entirely natural. But we should consider Sandy—and other recent extreme weather events – an early taste of a climate-changed world, and a grim preview of the even worse to come, particularly if we continue to pump more carbon pollution from smokestacks and tailpipes up into the atmosphere.
     Last weekend, millions of Americans prepared for the storm by turning to meteorologists to tell them where the storm would hit. The meteorologists relied on detailed computer models to form an accurate prediction of where it would hit and how strong it would be.
     We climate scientists use models too, and our results are remarkably consistent and remarkably dire. For example, our models predicted an increase in extreme precipitation with global warming, and that’s exactly what we have witnessed. In the northeast U.S. extreme precipitation has gone up 67 percent in recent years, due to the same rain-loading action that pumped up both Sandy and Hurricane Irene. Our models also predicted more heat waves, and again that’s exactly what we have gotten as the most extreme summers are now much more frequent around the world, setting the stage for intense heat waves.
     This new world is expensive – damage from Sandy will be in the billions of dollars, with estimates as high as $50 billion. In 2011, the United States broke a record for the most billion dollar weather disasters in one year, fourteen, totaling $47 billion dollars.
     It’s time to stop asking when climate change will arrive. It’s here, and we need to move aggressively to curb carbon emissions while also preparing for a changed world. We are at nothing less than a critical juncture.
     In addition to more extreme weather, failing to change our ways will mean extreme costs. Not acting on climate change could cost our nation more than 1 percent of GDP by 2025, or $218 billion a year, according to an analysis by Frank Ackerman, an economist at Tufts University. And it skyrockets from there, possibly to an estimated $1.8 trillion by 2100.
     Fortunately, scientists have outlined what is needed to meet this challenge. We need to cut industrial carbon pollution. There are several ways to achieve that goal, many of them also money-savers, and as scientists we stand ready to help policymakers figure out the best, most cost-effective ways to do so.

Dr. Bob Corell is a senior policy fellow for the American Meteorological Society and former Chair of the United States Global Change Research Program.
Dr. Jeff Masters is the founder and Director of Meteorology for Weather Underground and a former NOAA Hurricane Hunter.
Dr. Kevin Trenberth is a Distinguished Senior Scientist in the Climate Analysis Section at the National Center for Atmospheric Research.