There is a story that I hope is not apocryphal, told among anthropologists. It goes like this. A graduate student in Cultural Anthropology went to the field, to a site in the American Southwest, where he intended to document the lifeways of a group of Native Americans living there. On arrival at the field site, he was directed by helpful locals to the home of a very old man who, they said, knew all about the group’s history and culture. This would be a great place to start his research.
It is never too soon to talk about human caused climate change in relation to hurricanes. This is a bed we made and we are now sleeping in it.
Rather than yammering on and on about how a warmer atmosphere is a damper, but also more evaporation-inducing (and thus drying), and energetic atmosphere, and about how warmer air going over warmer sea water produces more and bigger storms globally, and all that, I’ll point you to some resources below.
But first I want to address two misconceptions: 1) that you can never attribute to a particular storm the effects of climate change THIS IS FALSE and 2) that climate scientists believe that Atlantic hurricanes will become less and less of a problem with climate change THIS IS ALSO FALSE.
On the attribution. Let’s say there is a disease with a 50% mortality rate. But then a treatment is invented that reduces that to zero. We use the treatment widely and nobody dies of it any more. Then, you get the disease, are cured, and go on a public speaking tour in which you espouse the greatness of this cure.
But one night, while you are speaking in front of a large audience, someone stands up and says, “Hey, wait one darn minute there! You might have been one of the 50% that would have lived! You can’t say that this cure did ANYTHING. Faker!”
The audience, realizing that the cure does not actually work, stands up and walks out.
Was that fair? Was what just happened in this scenario a honest, thoughtful turn of events?
With climate change it is a little like that. People who want to deny the importance of climate change, including journalists still stuck in the false balance mode (if there are Senators in the Senate claiming that human caused global warming is a hoax, then we must consider that as equally likely as what all the world’s scientists are saying), pull the attribution rabbit out of the hat all the time. Since you can’t yada yada. Even some climate scientists used to say this because the were badly trained in what to say.
Indeed, the binary (cure/not cured) I gave you above is not really like climate change. The fact that ALL the sea surfaces in the tropics and sub tropics — every single square centimeter — are on average (and in fact most of the time, for most of the seconds of most of the days, all year) anomalously warm, all of the tropical weather systems are affected all of the time. Fail to understand that at your peril.
The second falsehood, that Atlantic hurricanes will become less of a problem, is perhaps even more pernicious. There once was a study that seemed to show that some of the climatic conditions that would attenuate tropical cyclones, denying them the chance to form into hurricanes, would become more common in the Atlantic. This is probably true. However, the climatic conditions that cause tropical storms to form and advance to hurricane stage are also increased — different effects — and these effects have the added bonus of causing hurricanes to form much more rapidly and sometimes (perhaps often) grow much larger and, by the way, exist farther north. Indeed, if Florence does reach Category 5 for a short time today or tomorrow, it will be the farthest north Cat 5 hurricane ever in the Atlantic.
Here’s the thing. We will see periods of time when hurricanes that might have formed, say, 20 years ago, won’t. But we will also see periods of time when more and bigger and worser hurricanes form. The actual average number of hurricanes in the Atlantic has not gone down, but rather, stayed fairly stable, over recent decades. The frequency of large and dangerous hurricanes globally has gone up, and that trend is probably observable in the Atlantic.
Point is, we are not seeing a decrease in Atlantic hurricane activity or impressiveness, and we are seeing records being broken with respect to time to formation, size, strength, etc.
Climate Signals has a page on Hurricane Florence. They point out that sea level rise and coastal storms are a significant coastal erosion threat. warmer waters make for more and bigger hurricanes, keeping the hurricanes big longer, and making them form faster. These hurricanes are wetter.
Indeed, we have replaced the term “Biblical Flooding” with “Harvey Size Flooding” since we no longer have to imagine it.
Here is a helpful video:
This graph showing the relationship between sea surface temperature and hurricane activity.
About 20 million people are currently under a blizzard warning, and double that under a winter weather advisory, for a storm moving into the Northeast today and tomorrow, with snow falling though Wednesday. Thousands of flights have been cancelled. Wind will be at tropical storm force, and occasionally, hurricane force, and coastal flooding is expected to be epic. The total amounts of snowfall will be over a foot for a very large area, and well over that here and there, though this is very difficult to predict.
This is a strong low pressure system that will gather significant energy from a warm sea surface as it moves into the Atlantic.
This is a system that would normally not produce a lot of snow, but the odd configuration of the jet stream (once again) is moving the low pressure system through a pattern that will create an epic blizzard.
Storms of roughly this magnitude, in this the New York City area, have occurred in 1888, 1947, 1978, 1993, 1996, 2003, 2006, 2010. A similar pattern would emerge if the focal area was Boston. Weather Wunderground lists these snow events for New York City, indicating that half of the heavy events since the mid nineteenth century have occurred in the last 12 years:
26.9″ Feb 11-12, 2006
25.8″ Dec 26-27, 1947
21.0″ Mar 12-14, 1888
20.9″ Feb 25-26, 2010
20.2″ Jan 7-8, 1996
20.0″ Dec 26-27, 2010
19.8″ Feb 16-17, 2003
19.0″ Jan 26-27, 2011
18.1″ Jan 22-24, 1935
18.1″ Mar 7-8, 1941
Both the odd jet stream and the warm sea surface temperatures can be pegged as likely effects of anthropogenic global warming (AGW). This added to the clear pattern of more of these storms happening very recently strongly suggest that it is reasonable to characterize this storm as a “global warming amplified storm.” This is not unexpected.
I’m not sure if the sea surface temperatures in the region are at a record high, but they are very high. Over time, North Atlantic sea surface temperatures have certainly risen:
(a) Global annual mean sea-surface temperature (SST) anomalies from HadISST for the period 1870–2008 (Ref. 58)(thin black line). (b) Annual mean North Atlantic SST anomalies for the period 1870–2008 (ref. 58; thin black line). (c) The Atlantic multidecadal oscillation (AMO) index for the period 1870–2008. The modern AMO index4 is defined by subtracting the global mean SST anomalies (a) from the North Atlantic SST anomalies (b). Five-year running means are shown by heavy black lines with fill in all panels.
And here is the current sea surface temperature anomaly map for the region, showing current temperatures off New York and New England in the upper range:
This is inline with predictions the IPCC has been making for some time now. According to climate scientist Michael Mann, “The U.N. Intergovernmental Panel on Climate Change has found that Nor’easters like this one may grow stronger w/ human-caused climate change, as they are driven by the contrast between cold Arctic air masses and ever-warming ocean surface temperatures. We also know that ocean surface temperatures off the U.S. east coast right now are unusually warm, and there is no doubt that a component of that anomalous warmth is due to human-caused climate change. Those warm ocean temperatures also mean that there is more moisture in the air for this storm to feed on and to produce huge snowfalls inland. Climate change is making these sorts of storms more common, much as it is making Sandy-like Superstorms and unusually intense hurricanes more common. Asking whether these storms were caused by climate change, however, is asking the wrong question. What we can say is that they were likely made worse by climate change.”
Kevin Trenbeth, of the National Center for Atmospheric Research notes that the main reason there is a big blizzard coming to the northeast is that it is winter, but “it is warm over the oceans and the contrast between the cold continent and the warm Gulf Stream and surrounding waters is increasing. At present sea surface temperatures are more than 2F above normal over huge expanses (1000 miles) off the east coast and water vapor in the atmosphere is about 10% higher as a result. About half of this can be attributed to climate change.” I would add that the actual anomolies over large areas of the sea where this low pressure system will track are closer to 4 degrees.
There is a live blog at Weather Underground that you may want to keep an eye on, here. There, we see that current predictions for the region are:
New York City, NY: 18 – 24″
Boston, MA: 20 – 30″
Providence, RI: 20 – 30″
The National Weather Service has a page on the storm here.
, on Florence in which Mann points out ways in which climate modeling predicted greater severity of hurricanes. That set of predictions included, by the way, an increased tendency for Atlantic hurricanes to hit the US:
