The “end of the world” allegedly predicted by the Mayan calendar in December 2012 may be a myth, but 2012 had no shortage of catastrophes. We had the warmest year in history in North America, with record-breaking heat waves through much of the summer, and drought conditions approaching those of the Dust Bowl years. A July heat wave melted 97% of the surface of the Greenland ice sheet, the worst melting since satellite monitoring began 30 years ago. Arctic sea ice cover in September was at an the all-time low, beating the record set only back in 2007. 2011 was not much better, with Hurricane Irene flooding the Northeast, a large number of killer tornadoes (including deadly storms in Missouri and Alabama), 500-year floods in Nashville and Duluth, and severe wildfires all over the parched Rocky Mountains. It seems that the news is full of one unprecedented weather event after another, and those jokes about snowy winters a few years ago seem lame when most of the U.S. population sweltered through the heat waves of 2012.
And then along came Sandy. Having dodged a bullet with the less-damaging Hurricane Irene in 2011, many people in the path of Sandy were skeptical of the warnings of its power and size, and failed to take the warnings seriously. But Sandy lived up to its reputation and the damaged zone has still not recovered over two weeks later. The scale and degree of the destruction was unprecedented, and the monetary costs of the storm will certainly eclipse Hurricane Katrina or any other natural disaster in U.S. history when the final accounting is all done. More to the point, it was an unusually late storm; the hurricane season is typically done by November. Like Irene, it went much further north than the normal paths of hurricanes, which tend to focus on the southeastern U.S.
Although climate scientists have stressed over and over again that hurricanes like Irene and Sandy are expected product of global climate change, the climate deniers still cling to the technicality that we can’t blame Sandy entirely on climate change. It is true that individual weather events have multiple, complex causes so no single factor can be the sole culprit. And it is true that non-weather events, like an unusually high tide, helped contribute to Sandy’s enormous flooding and wave surge. But as a number of climate scientists have put it, the existence of Hurricane Sandy might have just been another unpredictable weather event, but the much greater size and intensity of Sandy is a result of climate change. As Jonathan Foley, director of the Institute on the Environment at the University of Minnesota, tweeted: “Would this kind of storm happen without climate change? Yes. Fueled by many factors. Is [the] storm stronger because of climate change? Yes.” Or as science blogger Greg Laden wrote:
“There is always going to be variation in temperature or some other weather related factor, but global warming raises the baseline. That’s true. But the corollary to that is NOT that you can’t link climate change to a given storm. All storms are weather, all weather is the immediate manifestation of climate, climate change is about climate.”
As prominent climatologist James Hansen of the NASA Goddard Institute wrote (referring to all the recent record-breaking climate events):
“Our analysis shows that it is no longer enough to say that global warming will increase the likelihood of extreme weather and to repeat the caveat that no individual weather event can be directly linked to climate change. To the contrary, our analysis shows that, for the extreme hot weather of the recent past, there is virtually no explanation other than climate change… The odds that natural variability created these extremes are minuscule, vanishingly small. To count on those odds would be like quitting your job and playing the lottery every morning to pay the bills.”
So why do climate scientists see the fingerprints of global warming in Hurricane Sandy? Consider the following:
1) Warmer oceans: anyone who understands a bit about hurricanes realizes that increased warmth in the tropical oceans promotes more intense hurricanes, and the world’s oceans have warmed dramatically since the first measurements were taken decades ago. Consider the figure below:
As MIT climate scientist Kerry Emanuel (a conservative Republican) first predicted in 1995, and has substantiated with additional new research in subsequent years, this is the main factor promoting more energetic and more damaging hurricanes, and indeed there have been more powerful and costly hurricanes in the past seven years than ever before. Consider the recent history of the Atlantic hurricane seasons. 2005 was the record-shattering year (breaking the previous record held by 2004), with so many storms they ran out of names and went to Greek letters for the first time, saw their first-ever South Atlantic hurricane, and they had to retire five names, including superstorms Katrina and Rita. In 2007, we had two Category 5 storms (largest possible size), and three more names had to be retired. 2008 was the fifth most active season in record, three more names had to be retired, and it was the only month when a major hurricane existed in every month from July to November. 2010 was the second most active hurricane season on record, with eight named storms in September alone. 2011 tied for the third most active season on record, with Hurricane Irene bringing storms much further north than previously. And 2012 is currently tied with 2011 for third most active season on record, with a record eight named storms in August, and Hurricane Sandy—and the season isn’t officially over yet.
2) More moisture in atmosphere: Warmer atmospheres carry more moisture, which makes hurricanes wetter and increases the potential of flooding. As climate scientist Kevin Trenberth explained:
“With every degree F rise in temperatures, the atmosphere can hold 4 percent more moisture. Thus, Sandy was able to pull in more moisture, fueling a stronger storm and magnifying the amount of rainfall by as much as 5 to 10 percent compared with conditions more than 40 years ago. Heavy rainfall and widespread flooding are a consequence.”
3) Higher sea levels promotes more flooding due to storm surge: Climate deniers often scoff at the idea that a rise of sea level is so terrifying, but it’s not the average rise of sea level that’s the problem. It’s the fact that if you start with a higher sea level, then the storm surge waves coming off a hurricane like Katrina or Irene or Sandy will flood a much greater region. Consider the figure below:
Long before sea level rises high enough to drown most coastal cities of the world, it will be high enough to make the storm surges more devastating—which will flood the cities in a different way.
4) The Arctic effect: The real surprise of Hurricane Sandy was another, unexpected effect of the warming and melting of the Arctic ice cap. As the Arctic warms, it changes oceanic circulation patterns, and causes the jet stream to shift southward. This southerly deflection of the colder jet stream air as it collided with the warm tropical air of Hurricane Sandy was one of the main reasons for the intensity of the storm, and why it dropped so much moisture in so little time.
So there you have it. Sandy could have been an ordinary storm in an earlier time before climate change, but it became a “Frankenstorm on steroids” thanks to warmer oceans, moister atmospheres, higher sea level, and the shifting of the jet stream due to Arctic warming. Thus, we got the conditions for “the perfect storm.” And climate scientists tell us that this is only the beginning of a new norm of superstorms, year after year. In the words of climatologist Dave Roberts:
“There is no division, in the physical world, between “climate change storms” and “non-climate change storms.” Climate change is not an exogenous force acting on the atmosphere. There is only the atmosphere, changing. Everything that happens in a changed atmosphere is “caused” by the atmosphere, even if it’s within the range of historical variability.”
And as Stephan Lewandowsky put it,
“We are living with climate change. It is happening now. Debating the extent to which Frankenstorm Sandy was put on steroids by climate change is a distraction. Nearly all weather events now have a contribution from climate change and it is up to us to manage and reduce that risk with mitigative action.”
And if you don’t believe climate scientists, you might consider the actions of the insurance industry. Insurers have no ideological axe to grind, but must prepare for realistic conditions in the future so they can insure their losses. The large international re-insurer Munich Re warned:
“Nowhere in the world is the rising number of natural catastrophes more evident than in North America.” … While many factors have contributed to this trend, including an increase in the number of people living in flood-prone areas, the report identified global warming as one of the major culprits: “Climate change particularly affects formation of heat-waves, droughts, intense precipitation events, and in the long run most probably also tropical cyclone intensity.”
Apparently, the recent spate of extreme weather convinces people much more than scientists talking about their data and issuing dire warnings, or climate deniers trying to obscure the nearly unanimous message of the climate science community. A poll taken the day before the November 6 election showed that 68% of Americans now regard climate change as a “serious problem,” up from only 48% in 2011, and 46% in 2009. Even Republican politicians like New Jersey Gov. Chris Christie and New York City Mayor Michael Bloomberg were warning about the dangers of climate change. It may be too much to expect the Congress to act upon this information when it is paralyzed by partisanship, but sooner or later the popular concern about tragic weather events and loss of life and property will force us to vote in politicians who respect what scientists have long been saying.