Tropical migrations

Solomon Hsiang and I have a new paper out in Scientific Reports.A blog post about it by Stacy Morford is on the Lamont site. The paper points out the ramifications of a basic fact about the structure of earth’s temperature for potential climate change-induced migrations of species, including humans. In one sentence: tropical temperature gradients are small so that it takes a long migration to cool off if you start near the equator.

This new paper is a little different than my usual, in that it’s about impacts of climate change rather than about the physics of weather and climate itself. It does connect the physics to the impacts, in that the uniformity of tropical temperatures is a consequence of basic geophysical dynamics and a fact that I have made extensive use of in my normal (purely meteorological) research. It’s a theoretical study and not to be taken as a prediction of any specific migration, but we think the main point is nonetheless relevant to more practical and realistic discussions on this topic.

The lead author, Sol Hsiang, got his Ph.D. at Columbia some years ago in our sustainable development program, and has gone on to become a star in the rapidly growing field of climate impacts. He deserves most credit for this paper; the only reason I could participate in a study like this is because he had the idea and kindly asked me to be involved.

Extreme event attribution

I have not been keeping up here the last few months. To start the catching up process:

During the fall and winter I was part of a committee convened by the National Academies of Science, Engineering and Medicine to perform a study on extreme event attribution. This is the science of making specific, quantitative statements about how a specific individual weather event was influenced by human-induced climate change. It was a wonderful experience working with my colleagues on the committee, most of whom I hadn’t known before, and (not having previously worked on attribution myself and thus not being an expert in it before we started) I learned a great deal. Not just about the subject matter, either – tt was my first NAS committee and very informative to see how the sausage is made. We think the report came out very well, and it seems to have been well received.

The report itself is available for free online in electronic form; hard copies cost money (and aren’t available yet). I wrote an op-ed for the Washington Post’s Capitol Weather Gang (thanks Jason Samenow!) to express some of my own perspective in a more informal way. Climate Central Chief Scientist Heidi Cullen wrote one for the NY Times, and my colleague on the committee (and former AMS President) Marshall Shepherd wrote one in Forbes. There was lots of other media coverage, easily found through your favorite search engine; here’s a piece on the Lamont web page by Stacy Morford.

On Thursday, April 7, I’ll be speaking at an event about the report with committee chair Rear Adm. Dr. David Titley and AP science reporter Seth Borenstein, moderated by Heidi Cullen, at the NAS Koshland Museum.

December 2015’s crazy weather

I’m in Oregon, where December has broken rainfall records east of the Cascades, and the Cascades themselves are deep in snow. I got to see some of it up by Mt. Hood yesterday on a Christmas Day family cross-country ski outing.


Though that was beautiful, I’m still sad to be missing the record-breaking warmth back east. (I like warm weather; it’s not an accident that most of my research over my career to date has been about tropical meteorology.) To help myself experience it vicariously, I wrote an op-ed piece for CNN about what the probable causes are. It has even been translated into Spanish.

Mumbai and Chennai

Last week I had an op-ed piece in the Times of India. It’s about the risk to the city of Mumbai from a tropical cyclone landfall and storm surge.

Mumbai is on the Arabian Sea, where tropical cyclones are relatively rare, and the city hasn’t been struck by a serious one in a very long time – well beyond living memory. If it were, though, the results could be catastrophic, as it’s both very low-lying and heavily developed right to the shore. This is exactly the recipe for an awful disaster: high vulnerability, low awareness of the risk.

I had the opportunity to write this thanks to an invitation from the great writer Amitav Ghosh, who was the guest editor for this issue of ToI. I was thrilled to get an email this past summer from Amitav, in which he said that he had enjoyed my book Storm Surge and wanted to talk to me about climate change and the risk to Mumbai. This was related to a series of lectures he was to give (now has given) at the University of Chicago in which climate change is a central theme, and which will be turned into a book in due time.

Amitav and I subsequently met to discuss the science of climate change and tropical cyclones in my apartment in New York as he was making his way to Chicago. By this time I had begun making my way through his books. They are wonderful. Themes of history, environment, ecology, and climate are woven through them, and cyclones figure prominently as plot elements in at least a couple. I got several copies signed.

So now the op-ed has come out. (The issue also has an interview with Amitav himself, and a piece by Christian Parenti on the relationship between climate and Naxalite violence in India.) Coincidentally, my piece on hypothetical flooding of Mumbai appeared at the same time as a new burst of extreme rainfall was causing very real flooding in Chennai, on India’s opposite coast.


Infrared satellite image from November 17, showing a disturbance that one of the earlier waves of flooding in Chennai.

The Chennai flooding had begun a couple of weeks earlier, when cyclone BOB3 (“BOB” stands for “Bay of Bengal” – this storm was never strong enough to get a proper name) came ashore. This is the storm that had formed in the Bay of Bengal while cyclone Megh was in the Arabian Sea, heading for Yemen. Some forecast models predicted that BOB3 would cross the subcontinent and reach the Arabian Sea itself. But it didn’t do that. It hung around over land as a disorganized disturbance, dumping lots of rain.

Then another major burst on December 1 – a foot of rain fell on that one day. This after 40 inches in November (from BOB3 and a couple of other storms) – three times the average in Chennai for that month, and about equal to New York City’s annual average.

While it was a tremendous amount of rain, some argue that the flooding was made much more severe by careless development of Chennai in recent years, as floodplains and drainage channels have been paved over. The story is similar in Mumbai, where destruction of mangroves and river channelization have been blamed for similarly exacerbating the flood which occurred there in 2005 (also driven by rain, not storm surge, nor related to a cyclone) – and will similarly make things worse if, someday, a cyclone causes a major storm surge there. And to New York City, for that matter, where real estate development is now hot again in some of the areas worst hit by Sandy. I don’t know that op-eds or books can make much difference in the face of such indifference to risk, but it’s worth trying.

Review of Storm Surge by Brian Mapes in BAMS

In current issue of the Bulletin of the America Meteorological Society is a review of Storm Surge by Brian Mapes. It’s a beautiful, thoughtful, insightful review (I say from my totally unbiased perspective). Brian saw everything I had hoped the reader would see in the book. Now, BAMS is not the New York Times; this won’t sell thousands of books. But it means a great deal to get this kind of approval, from such a brilliant colleague, in a core publication of my own field. I didn’t write the book for other meteorologists, really, but if they didn’t like it, I’d know I had done something wrong. Thanks Brian!