In the wake of Hurricane Sandy, liberals have been ever eager to finger climate change as the cause, and claim the tragedy is a dispositive argument for what we need to do about global warming. Here’s the problem, though: As Patrick Michaels has written on NRO, scientists hardly have irrefutable evidence to attribute storms to global warming. There’s some reason to think there’s a connection, but it’s hardly an, er, watertight case.
Or, as a Sunday NPR report Greg Pollowitz pointed out in this space put it:
There is a hierarchy of weather events which scientists feel they understand well enough for establishing climate change links. Global temperature rises and extreme heat rank high on that list, but Hurricanes rank low. As the IPCC special report on extreme events put it “There is low confidence in any observed long-term (i.e., 40 years or more) increases in tropical cyclone activity (i.e., intensity, frequency, duration), after accounting for past changes in observing capabilities.” . . .
This is not to say progress isn’t being made. One thing that does seem clear is that warmer oceans (a la global warming) mean more evaporation, and that likely leads to storms with more and more dangerous rainfall of the kind we saw with Hurricane Irene last year. In addition, a paper published just last month, used records of storm surges going back to 1923 as a measure of hurricane activity. A strong correlation between warm years and strong hurricanes was seen. Thus if you warm the planet, you can expect more dangerous storms.
Sandy was already a dangerous storm just by virtue of being several storms randomly colliding, but it surely did benefit from warmer ocean water, which can supercharge storms. But as one meteorologist explained to the New York Times, “natural variability very likely accounted for the bulk of that temperature extreme.” He went on to explain that, “my view is that a lot of this is chance . . . It relates to weather, and the juxtaposition of weather systems.” Or, as the NPR report put it, “for hurricanes, however, sticking to the science means it is still hard to point to an individual storm and say, yes! Climate change!”
But of course, that didn’t stop Mother Jones from doing just that. Chris Mooney glibly cites his own 2007 book, which discussed the possibility of sea-level rises’ contributing to events like Sandy:
As I wrote:
Even as we act immediately to curtail short term vulnerability, every exposed coastal city needs a risk assessment that takes global warming scenarios into account…Scientists at the NASA Goddard Institute for Space Studies in New York have been studying that city’s vulnerability to hurricane impacts in a changing world, and calculated that with 1.5 feet of sea level rise, a worst-case-scenario Category 3 hurricane could submerge “the Rockaways, Coney Island, much of southern Brooklyn and Queens, portions of Long Island City, Astoria, Flushing Meadows-Corona Park, Queens, lower Manhattan, and eastern Staten Island from Great Kills Harbor north to the Verrazano Bridge.” (Pause and think about that for a second.)
No need to pause and think any longer—last night, just over five years later, much of it came to pass. And indeed, climate change, a topic embarrassingly ignored in the three recent presidential debates, made it worse.
Now those things did pretty much happen — not because of a Category 3 Hurricane and a hypothetical sea-level rise, but because of a tropical storm with an exceptional storm surge, which, it appears, happened to hit New York with full force at the worst moment, last night’s 9 p.m. high tide. And the “1.5 feet of sea level rise” projection that his book considered as a consequence of climate change didn’t cause Sandy, of course, since it hasn’t happened since the 2006 study (though it could, over the next few decades). He goes on:
Last night, southern Manhattan reportedly received a 13.88 foot storm surge, a record high and more than enough to flood much of the city. We’ve all seen the pictures. What’s more, according to Ben Orlove, director of the Master’s Program in Climate and Society at Columbia University, about a foot of that surge would not have been there if not for the sea-level rise already caused by climate change over the course of the 20th century.
Here, Mooney completely loses the thread: Yes, Manhattan experienced a record storm surge last night. But that’s a storm surge, which means increase above whatever the tide would be at a given hour and by definition has nothing to do with sea-level rise. Some parts of New York might be drier right now had the harbor’s level been a foot lower than the last century’s changes have left it, but that’s water under the bridge.
He cites an argument by Ben Orlove, a Columbia anthropologist, that some of the surge is due to climate change, but it doesn’t scan: Orlove explains that sea level in New York harbor has risen one foot over the last century, and “when this foot is added to the four feet of the high tides at the full moon, it reaches five feet, more than half the height of the sea wall.” This is good addition (though Orlove offers no evidence, here, for the one-foot rise’s being due to anthropogenic climate change), but it has nothing to do with what level of storm surge, or sea level, is necessary to devastate Manhattan, or Mooney’s earlier point about potential sea-level rises. Subtract that foot of supposedly man-made increase in the 20th century, and you still have a 13.88-foot storm tide (the high-water mark of high tide plus the storm surge). In fact, Mooney’s NASA estimates actually just demonstrate that much of New York City would be flooded by a Cat-3’s storm surge, but the IPCC’s projected sea-level rises they use wouldn’t worsen the city’s situation much at all.
The doomsday scenario Mooney greets so gleefully didn’t come about because of sea-level rises we could see from global warming in the coming decades or because of change over the last century, but because of record surge from one bad storm at high tide. Sandy showed us what flooding lower Manhattan looks like; it doesn’t prove that burning fossil fuels will make the flooding of lower Manhattan more common.
But can’t we blame Sandy itself on global warming? As explained above, it’s also difficult to draw a plumb line between Sandy and higher global temperatures. Indeed, Sandy was not an exceptionally vicious storm at all: It was the combination of several storms, like 1991’s Perfect Storm, and made landfall in a vulnerable, populated place, like Katrina.
I personally am much more sympathetic to arguments about anthropogenic climate change than many conservatives are, but that’s because I believe such claims have a solid scientific argument on their side. There may be a similarly compelling argument behind higher temperatures causing more damaging storms like Sandy (though there isn’t, yet), but that still wouldn’t make the Sandy hysterics scientific. Climate-change partisans may score short-term points, but ultimately undermine their legitimacy, by claiming tragic, one-off events as points for their cause.