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.

Patricia’s ultra-fast intensification

I have a piece in CNN today about the incredibly fast jump that Hurricane Patricia made from tropical storm to what some people are saying should be called “category 7”. I point out that this case shows vividly why we need advances in the science of hurricane intensity prediction, at the same time as funding for this work was severely cut earlier this year. And, I compare Patricia to The Hulk.

Earlier, before landfall, Allison Wing and Chia-Ying Lee wrote an expert but accessible analysis of what the storm was doing and how the forecast models failed to capture it.


Sudden excitement in the forecast

Update: Tropical Depression Eleven has already been upgraded and is now Tropical Storm Joaquin.

Some weather models shifted their predictions today from what they had been just before. Now New York City, along with much of the rest of the northeast US, is in the headlights of a weather event with some potential. We are now in the forecast cone of uncertainty of a tropical cyclone: currently it’s Tropical Depression Eleven, could intensify to become Tropical Storm Joaquin. Here is the track forecast map from the National Hurricane Center:


There is still quite a lot of uncertainty with this system, with the GFS model predicting it to be less likely than the ECMWF does that we’ll be hit by this storm. There are faint echoes of Sandy in that model disagreement – the EC predicted landfall earlier than GFS did then too. It doesn’t look like Eleven/Joaquin stands much chance of becoming an event of that magnitude, though, at least not as a wind or surge event (though never say never, or at least not yet).

There does seem to be good potential for heavy rain. Maybe very heavy, as tropical moisture funnels up from the south into a cold front that will be hanging around our region for a few days. NOAA’s precipitation forecast for the next five days puts over five inches of rain on a very large stretch of real estate from the Mid-Atlantic up to northern Maine:


Some model runs are producing numbers as high as double that – around ten inches – for NYC. This is perhaps unlikely, but possible.

The media is starting to pick up on this. Jason Samenow of the Capital Weather Gang has a nice summary; has picked it up; and here is a local NYC TV take on it. From a quick scan, this coverage looks reasonable. It’s giving a sense of what the more extreme outcomes could be, while clearly stating that the uncertainties are still significant. This is as it should be. This is in the “stay tuned” category.

Urgency and Uncertainty in Rolling Stone

Eric Holthaus has a recent piece in Rolling Stone enitled “The Point of No Return: Climate Change Nightmares Are Already Here.” The subtitle is “The worst predicted impacts of climate change are starting to happen — and much faster than climate scientists expected.”

It’s a good article. But it highlights the difficulty of talking about current extreme weather events and their relation to human-induced climate change. On the one hand, the essential message of the piece is to communicate urgency on climate and need for action. This is right and appropriate. And sentence by sentence, the individual statements about specific weather and climate phenomena are accurate (at least those where I have adequate expertise to make an evaluation).

On the other hand, the piece implicitly attributes a lot of individual weather and climate events – all of those it mentions, really, which is a long list – to human induced climate change. Some of those attributions are justified, but others aren’t.

In the cases where the attribution isn’t justified, Holthaus doesn’t explicitly make it, not line-by-line in the sentences talking about those events. I couldn’t find anything outright wrong at that level. The piece was, clearly, researched and written quite carefully and with deep respect for the science. But the attribution is there implicitly, through the piece’s headline, its subtitle, and its overall framing.

I’ve added some annotations at the site Climate Feedback (my annotations and others’ on this piece are not visible yet, as far as I can tell; soon, I think), a new site designed for scientists to evaluate the science content in popular articles on climate. Two of my comments are about Holthaus’ discussion of the ongoing El Niño and positive phase of the Pacific Decadal Oscillation. These two are enough to make the point I’m interested in here.

These two climate phenomena, manifest by slow changes in the sea surface temperature in various parts of the Pacific ocean are indeed having major impacts, as described well in the article. But most climate scientists consider these phenomena to be essentially natural. We can’t be certain that the current instances of El Niño and the Pacific Decadal Oscillation aren’t in any way connected to human induced climate change, but there is no convincing evidence of such a connection, to my knowledge. Holthaus doesn’t say there is one, but to my eye it’s clearly implied. The title and subtitle, as well as the overall framing of the piece, say that it’s a list of impacts of “climate change” – which presumably most will understand to mean “human induced climate change”.

I’m being critical on this issue because it’s one I struggle with myself, and because Holthaus is a thoughtful, serious and committed writer on climate, one who actively seeks criticism from scientists (I understand that he asked Climate Feedback to evaluate his piece). And because while I read the piece as making some implied claims that are outside what science can justify, I agree completely with its bottom line, and appreciate the force with which it comes across.

Human-induced climate change is real, is a grave threat to human society, and is already having significant impacts now. Some of the events Holthaus describes almost certainly do have some imprint of human influence: heat waves and ocean acidification, for example. And natural and human influences can’t be completely untangled. While the heat, drought and wildfire in the west now are likely caused in large part by natural variations in the Pacific sea surface temperature (El Nino and Pacific Decadal Oscillation), greenhouse gas warming adds extra heat, making the impacts worse.

And regardless of the causes of individual extreme weather and climate events now, the disasters they cause still tell us something about our vulnerabilities, and that is relevant to the longer-term climate change question. The human influence will grow larger in the future, as warming proceeds. It will eventually make some kinds of extreme events significantly, detectably more frequent or more intense, even if we can’t clearly detect that influence in individual events of that type happening now. (Tropical cyclones are a good example of this.) The current events can rightly be seen as harbingers, if nothing else.

Holthaus writes quite a bit about the recent paper by James Hansen and colleagues, which warns that sea level rise may occur much sooner and more severely than most of us had thought. This paper is controversial, and not yet even through peer review. But in my view it deserves the coverage it gets, here and elsewhere – its predictions may or may not be right, but it seems pretty clear that we can’t rule them out. Contrary to denialist lines of argument, the uncertainties in climate projections should make us more worried, not less.

What if Holthaus had made a more concerted effort to avoid any implication of human influence on events to which it wasn’t justified? In a piece with the title and subtitle that this one has, the simplest way to do that would have been not to write about those events at all. That would have meant leaving out some of the most serious and visible disasters going on right now in the US, where the main readership for this piece presumably is. Alternatively, the piece could have had a different title and subtitle (my guess is that these were written by an editor rather than by Holthaus himself), one that communicated that the piece was about events of both natural and human origins. Either way, would the sense of urgency have been diluted?

Professional scientists are sometimes criticized for under-communicating the urgency and reality of climate change, especialy when we talk about current extreme events. This criticism is often fair in my view. We talk so much about the uncertainties that we leave nonscientist audiences with the feeling that we don’t know anything. We do this, I think, because we are used to talking to each other. Being clear about uncertainties is an inherent part of scientific practice. Also, our colleagues already share our knowledge and understanding of the big picture on climate change – the consensus is real – so we don’t feel a need to restate that. We fail to recognize that that underlying knowledge is not shared outside our professional circles, and that it’s often appropriate to emphasize what we do know more than what we don’t.

Journalists, on the other hand, are often criticized by scientists (and others) for overstating the connection of extreme events to climate change by glossing over uncertainties – as I have done here, in my first few paragraphs above. This is also often fair, and as with scientists, similarly traceable to the daily realities of their jobs. Journalists are under great pressure to make it current, make it exciting, keep it simple. It’s easy to see how that leads to a little exaggeration and overstatement, whether by implication or outright.

If there’s a perfect solution I don’t know it. I’m glad that writers like Holthaus (and many other good ones) are grappling with the science and doing their best to keep it accurate while still getting the essential message on climate into the popular press. I don’t love everything about this Rolling Stone piece but I think we need more like it anyway.

Full disclosure: Eric Holthaus is an alumnus of Columbia University, where I teach, though I didn’t teach him when he was here and haven’t met him in person to my knowledge. He has interviewed me a couple of times for other pieces he has written, though not for this one in Rolling Stone. He wrote a very kind review of my book when it came out last fall.