As communities from the Carolinas to Maine brace for high storm surges, winds and downpours, there’s a growing climate discussion building around #Frankenstorm, which is the favored Twitter handle for the extraordinarily vast and potent nor’easter that is evolving as Hurricane Sandy, already a killer, collides with an Arctic cold front.
You can track specific developments in and around New York here and follow the details of the storm’s track and impacts via Jeff Masters, the Capital Weather Gang and Weather.gov.
But what is the role, if any, of greenhouse-drive global warming in this kind of rare system?
It’s easy to say, as some climatologists have, that “climate change is present in every single meteorological event.” As you’ll hear below, some climate scientists are telling me this event is precisely what you’d expect following a summer in which much of the Arctic Ocean was open water.
But there remains far too much natural variability in the frequency and potency of rare and powerful storms — on time scales from decades to centuries – to go beyond pointing to this event being consistent with what’s projected on a human-heated planet. [*Adam Frank posted a great piece on the NPR blog on other factors complicating this question.]
While the echo of Frankenstein in that Twitter moniker can imply this is a human-created meteorological monster, it’s just not that simple.
There are several areas in which greenhouse-driven warming is thought to be a potential influence. The first is in the buildup of heat in southern surface waters. A paper published earlier this month in the Proceedings of the National Academy of Sciences was the latest to draw this conclusion, in this case through detailed analysis of storm surges recorded by Atlantic coast tide gauges:
We find that warm years in general were more active in all cyclone size ranges than cold years. The largest cyclones are most affected by warmer conditions and we detect a statistically significant trend in the frequency of large surge events (roughly corresponding to tropical storm size) since 1923.
But on longer time scales, the situation is murky because so many factors shape the formation and growth of tropical cyclones. I wrote in 2007 about a Nature paper by Jeff Donnelly of the Woods Hole Oceanographic Institution and others. Here’s the core conclusion:
Over the last 5,000 years, the eastern Caribbean has experienced several periods, lasting centuries, in which strong hurricanes occurred frequently even though ocean temperatures were cooler than those measured today, according to a new study.
That’s the Caribbean, of course.
What about the Northeast? Here’s Hurricane Sandy. Last year was Hurricane Irene and then there was Hurricane Floyd in 1999. But when you look back in time in this region, big questions arise about just what constitutes a superstorm.
As I’ve written before, the great tropical storm and floods that devastated Vermont in November 1927 (and after Irene) appear to have been minor compared to repeated past hill-scouring superfloods, according to an important study of lake-bed sediments revealing storm patterns and intensities in recent millenniums.
Here’s the lede from my story on that paper, published one decade ago:
Four times since the last ice age, at intervals roughly 3,000 years apart, the Northeast has been struck by cycles of storms far more powerful than any in recent times, according to a new study. The region appears to have entered a fifth era in which such superstorms are more likely, the researchers say.
The other questions related to human-driven climate change are focused on the impact of reduced…