In following the news coverage of Hurricane Sandy, I was struck by a strange reversal in reporting from before and after the storm. In the days leading up to landfall, the effect of climate change on the likelihood, strength or impacts of the storm was largely ignored; in accounts of the damage post-Sandy, the subject of climate change has been routinely raised. Maybe it was considered inappropriate to speculate on causes while there was imminent danger, maybe it’s the desire, following great destruction, to have somewhere to affix blame, or maybe I’m simply mistaken and there hasn’t really been a significant change in coverage before and after the storm. But from my perspective, the coverage of the storm has mirrored the general attitude toward climate change in America: 360 days of the year, we can’t afford the time — much less the cost — of reducing our dependence on fossil fuels, but after disaster hits, all resources will be brought to bear with impressive efficiency and generosity. In this election season, it is a seen as a liability to have previously called for cuts to FEMA, but increasing coal production is hugely popular.
Regardless, since times like these are when people are naturally thinking and talking about climate change, let’s tackle the most frequently asked questions:
First, is Hurricane Sandy evidence that the planet is in fact warming? Not really. This storm certainly could have happened if the climate had not been changing over the past century, or even if over that time the earth had been cooling.
For climate change advocates, it’s not even a wise question to raise. The truth is complicated: regarding specific weather events, global warming might be more accurately termed global weirding, producing all sorts of counterintuitive changes, such as warmer winters yet more frequent blizzards, and greater rainfall yet more frequent drought. And a complicated reality isn’t often a winning argument when trying to change someone’s mind. More important, we don’t need confirmation from recent weather to know that climate change is real, or that human activity is the cause; we have decades of long-term climate data and thousands of scientific studies to demonstrate that.
Second, was this bizarre Frankenstorm caused by climate change? That one is a little trickier. Maybe? Definitely partially? Unseasonably warm ocean water certainly contributed to the power of the tropical depression while out at sea. Ocean surface temperatures while the storm was forming were about five degrees higher than normal for that time period. Over the past century global ocean surface temperatures have risen a few degrees, so one could say that global warming caused a portion of the extra five degrees of warmth in the ocean on those critical days. But here we’re back to the problem from before: the conditions that led to the storm are consistent with a warmer planet, but still could have occurred without it. It’s probably reasonable to say that climate change contributed to the intensity of the original hurricane, and the ability of such a storm to form this far north or this late in the season. Beyond that, there just isn’t yet enough evidence to attribute the monstrous aspects of this hybrid storm to climate change.
What is more certain is that the extent of the damage was exacerbated by the effects of climate change. The flooding and beach erosion were largely the result of the storm surge, which was both huge and remarkably long-lasting, bolstered by several high tides occurring close to a full moon. And this storm surge was unequivocally larger due to sea level rise. Global average sea level has risen about eight inches in the past century, but seas are rising (and will continue to) much faster in the Northeast due to changes in wind patterns and natural subsidence of the tectonic plate on which we sit. A recent study from the USGS found that since 1980, seas have risen three to four times faster in the Northeast than the global average.
And finally, will climate change lead to more frequent storms like this in the future? The simple answer is that we truly don’t know. Unlike the basics of climate change, there is no scientific consensus here. Right now, the preponderance of evidence suggests that hurricane frequency on the Eastern seaboard may stay the same, or even decrease, but the average intensity (or frequency of really big ones) could increase. The largest factors going into this mixed forecast are rising ocean surface temperatures that create more energy to form and feed tropical cyclones, offset by changes in atmospheric circulation patterns that change the trajectory of the storms or even cause them to tear apart due to wind shear.
In the end, the single most important thing to take from Sandy relative to climate change is the expanded damage from otherwise normal storms. Coastal erosion and property damage are already set to increase due to loss of wetlands, which buffer beaches by absorbing storm surge energy, and continued coastal development, which results in short-sighted shoreline armoring that protects one property while weakening the resilience of down-current beaches. Add in sea level rise — over the next century expected to be about three feet globally, but much more locally — and the damage grows rapidly. It is true that sea level rise is and will continue to be a small fraction of the total storm surge from a major hurricane. Sandy, for example, reached 13 to 14 feet in New York city and coastal New Jersey. But in many ways, those last few inches (growing to feet at present) are the most important ones, allowing the surge to reach higher and deeper inland, and stay there longer, where human structures and the natural environment are simply less prepared for water.
Jeremy Houser is communications coordinator for the Vineyard Conservation Society, and is currently preparing a research report on climate change impacts on the Vineyard.