What Role Did Climate Change Play in Superstorm Sandy?
BY Anya Khalamayzer
Superstorm Sandy, a “perfect storm” that was caused by an unusual combination of seasonal weather phenomena converging above the Northeast, has stirred some conversation in the media about whether the storm was caused, or made worse, by climate change.
Scientists have long warned about the risk of a deadly hurricane over the Tri-State area, which would suggest Sandy could be an expected weather event. But recent studies, including a report co-authored by MIT climate scientist Kerry Emanuel in February 2012, note that climate change could combine with the effects of storm surge to cause 100-year-flooding to occur every two decades in New York, suggesting that an event like Sandy may be more than just a long-expected storm.
Insurance, climate and modeling experts weigh in on the role climate change may have played in Superstorm Sandy.
Robert Detlefsen, Ph.D., vice president of public policy, National Association of Mutual Insurance Companies: “The problem that arises when we start talking about whether climate change ought to be considered a separate determining factor in the likelihood of extreme weather events is that nobody knows how particular geographic regions will be affected in the near-term. I would question the assertion of people who have definitively stated that Sandy was caused by climate change as there are many factors responsible for causing any weather event.
“However, one hopes that that we have learned our lesson and will take further steps to determine the laws regulators must adjust in order to allow coverage to continue being written in at-risk areas. The North Atlantic seaboard will be hit by major windstorms in the future, but our society has a short memory, so as other issues come to dominate the news insurers hope policymakers don’t lose sight of the need to address what came to the fore when Sandy came to town.”
Tom Larsen, senior vice president and product architect, Eqecat: “Were the effects of Sandy exacerbated by climate change? Yes, absolutely. Was Sandy caused by climate change? That remains unclear. It certainly wasn’t predicted by our models. There is speculation that steering pressure coming from the north was linked to melting Arctic sea ice, however there is insufficient data- compelling but not convincing- to give us great certainty about it.
“Sea level rise due to climate change does influence how far a storm surge travels. Sandy set a new record at the Battery Park indicator for the first time in 50 years with a 14 foot surge, or four feet higher than the last one set by Hurricane Donna. Melting sea ice has caused a sea change of six to eight inches, which is just a fraction of that total shift. Also, while we did have abnormally warm Atlantic waters at this time of year, it was just one necessary ingredient for a storm like this.”
Dr. Bob Corell, senior policy fellow, American Meteorological Society: “You can’t simply state that climate change caused Sandy, but it made her more intense. It’s very important to make the connection between weather extremes and the warming of the planet, because warmer water contains energy that drives hurricanes.
“Cyclonic storms pick up that energy as they come across the Atlantic from the African coast on their way to the Caribbean, where measurements taken over the past several decades show that water surface temperature has warmed by as much as two degrees.
“That may not sound like much, but it is a huge amount of energy when it is spread over an ocean and sucked into the atmosphere. Put another way, we will have far more Category Three to Five storms than we used to. Sandy was only a Category One storm, but it combined with two other systems that were amplified by the warm atmosphere to become the hybrid that it was.”
Cynthia McHale, insurance program director, CERES:“Many models have been created to understand New York City’s vulnerability to sea level rise, and it has been predictable and predicted that at some point lower Manhattan would be flooded.
“No one knew when it would be hit or how badly. There were many factors in play, including sea level rise and the increased risk of intense Caribbean hurricanes due to higher ocean temperatures. Some scientists also tied in cold air coming up from the Arctic early in the season.
“Underwriters and reinsurers think of the worst-case risk scenario and how it will affect the corporate capital for which they’re on the line. In this case, there was enough concern to say that there is likely to be severe, weather-related flooding down the coast, even without concrete evidence for climate change. And the fact that the term is so politicized steers the industry away from it without first understanding what the risks are.”
Dr. Tim Doggett, principal scientist, AIR Worldwide: “A number of factors influence how active a season is, including sea surface temperatures and wind shear, and whether these are affected by man-made climate change remains uncertain. 2012 was an indeed active in terms of number of tropical storms that formed in the Atlantic basin, but only an average season in terms of the number of storms that actually made landfall in the U.S.
“While there are theories that climate change may increase losses from natural catastrophes in certain regions of the world, as of yet, there is no definitive indication that the frequency of landfalling hurricanes is increasing. AIR scientists have found that variations in Atlantic sea surface temperatures account for less than 1 percent of the variability in U.S. hurricane landfalls. Instead, mid-level steering currents, which are highly variable and unpredictable because they are determined by short-term weather patterns, are responsible for some 80% of the variation in storm tracks.”
Kerry Emmanuel, climate scientist, MIT (from an interview with Slate): “Sandy is an example of what we call a hybrid storm. It works on some of the same principles as the way hurricanes work but it also works on the same principles as winter storms work. Hurricanes and winter storms are powered by completely different energy sources. The hurricane is powered by the evaporation of sea water. Winter storms are powered by horizontal temperature contrasts in the atmosphere. So hybrid storms are able to tap into both energy sources. That’s why they can be so powerful.
“My profession has not compiled a good climatology of hybrid events […] We don’t have very good theoretical or modeling guidance on how hybrid storms might be expected to change with climate. So this is a fancy way of saying my profession doesn’t know how hybrid storms will respond to climate. I feel strongly about that. I think that anyone who says we do know that is not giving you a straight answer. We don’t know. Which is not to say that they are not going to be influenced by climate, it’s really to say honestly we don’t know.”
Chris Hackett, policy expert, director of personal lines, Property Casualty Insurers Association of America (PCI):
“Rather than looking at the specific cause of any one event, events like Sandy and Irene last year drew attention to the need for stronger building codes […] As communities look to rebuild, it’s also an opportunity to revisit responsible land use policies around the coast- what changes could be made for when next Sandy comes through the area? It’s probably not a matter of if but when, even if it doesn’t occur in the next 10, 15 or 20 years.
“It’s difficult to pinpoint whether any particular weather event is related to climate change, because you don’t know if it had. It’s not about climate change; it’s about taking care of people’s needs. I’m not sure that models can predict 15 years ahead. We try to work more from actual historical loss data when setting rates as opposed to projecting into the long-term future of weather events in any geographical area.”