‘Sea-Level Rise To Make Things Worse In Mumbai Within Decades’

Adam Sobel, an atmospheric scientist at Columbia University, highlights the danger to coastal cities like Mumbai and Kolkata as sea levels continue to rise and climate change affects storm patterns.

New York/Bengaluru: In 2015, India-born author Amitav Ghosh, researching his latest book, wrote to Adam Sobel, an atmospheric scientist at Columbia University in New York. Sobel, 52, studies extreme weather and climate. Could Mumbai be hit by a cyclone, Ghosh asked Sobel. 

In his book ‘The Great Derangement: Climate Change and the Unthinkable’, Ghosh looks at coastal cities around the world, questioning why they were built with scant regard to extreme weather events such as cyclones. One of his main arguments is that colonisation disregarded local knowledge of weather.

Ghosh then asked Sobel to provide a scientific answer: Was Mumbai built the way it was because the odds of cyclonic storms were virtually nil in the Arabian Sea? Sobel decided to conduct a study. Yes, Mumbai could be hit by a cyclone but the probability of that happening in any given year is slim, his team of researchers found. They did not, however, look at the changes in storm patterns due to climate change. 

Global warming has led to changes in ocean temperatures, including in the Arabian Sea, causing both sea-level rise and changes in rainfall over India. With this, the possibility of a cyclone making landfall along India’s western coastline is inching up, a September 2019 report from the Intergovernmental Panel for Climate Change (IPCC)--the United Nations’ body set up to assess science related to climate change--said.

India’s west coast sees less cyclonic activity than the eastern coast along the Bay of Bengal. Of all the cyclones that develop in the Bay of Bengal, over 58% hit the east coast and beyond, while 25% of the cyclones that develop in the Arabian Sea reach the west coast, according to government data. Of those in the Arabian Sea, most head northwards, towards Gujarat, and take place in October and November.

Nearly 5,700 km of India’s 7,500-km long coastline is highly vulnerable to tropical cyclones, according to government data. Some 320 million Indians--or a quarter of the country’s population--are vulnerable to cyclone-related hazards.

A few weeks ago, around the time when world leaders were debating climate action at the UN, IndiaSpend caught up with Sobel at his office in Columbia University. In an interview, Sobel spoke about the latest science on extreme weather events and touched on how coastal real estate prices around the world have begun to respond to what scientific evidence says: Living close to the coast is not a good idea, with sea levels and the frequency of extreme weather events going up. 

Edited excerpts from the interview:

In The Great Derangement, Amitav Ghosh looks at climate change through the lens of stories, history and politics, and elaborates on how local knowledge of the weather and climate was disregarded when a lot of the colonial cities were built. Looking at cities such as New York and Mumbai through the lens of science, do you find merit in that argument? 

That point that Amitav makes in The Great Derangement is one of the most profound ones. It gave me a new understanding of the issue in terms of an appreciation of the historical context.

Climate scientists like me, we talk a lot about sea-level rise. We worry a lot about sea-level rise because it is clearly going to be one of the biggest, the most egregious and obvious ways that climate change will affect people. We have so many people living on low coastlines. Eventually, some of those [cities] are going to be permanently under water, but long before that happens, they are going to be inundated more regularly by extreme events--whether it be storms that in the past wouldn’t have caused so much flooding because the sea levels started lower and so the storm surge didn’t have as much impact, or even just tides.

We talk a lot about how coastal cities are at risk and that’s probably because a huge number of people live in coastal cities--there is a lot of valuable real estate, a lot of valuable economic activity in coastal cities. 

What cities are most vulnerable differs whether we are worried about people or dollars. New York, Shanghai, Mumbai, Kolkata: these are the places. What Amitav pointed out, which I hadn’t appreciated before, was that these are all colonial cities built roughly around the same time in history. 

Before that, if you look at the older cities, they are inland, like Paris and London are. Or Beijing, for instance.

So, the empire [British] felt that being on the coastal cities is strategically valuable. The argument was that people who lived in these places for a long time had some kind of respect for the sea, understanding that it was dangerous.

In Mumbai, before the British, they were just a bunch of islands. A couple of them had hills but mostly they were very flat. All this stuff now that’s being developed along Thane creek where they are putting the new airport, that is all very low marshy stuff. Why? Because that’s the only thing that is left. And there is a reason for that. Similarly, if you look at where the slums are, Dharavi for instance, they are basically the old river beds. You can go to Dharavi and see the old customs house. Somebody would have to point it out to you or you wouldn’t know it. It is the 19th century customs house. What a customs house means is that you would come up on a boat in a river and you would pay a tax. And now, there is no river there.

Coastal real estate is really valuable, so you have the richest people on the coast--like in Marine Drive--but it is also kind of the worst. It is risky and marginal land that is not completely stable and safe to build on.

You can build on it and you might be fine for a while, or you might not. 

What kind of future are these cities staring at and how long into the future is it?

It is hard to answer that with precision. The rate of sea-level rise is uncertain. We use [the year] 2100 as a benchmark for no particularly good reason but just to pick some benchmark which is in common use. The estimates of global sea-level rise for 2100 compared to pre-industrial time are between 1-2 feet at the low end and 6 [feet] on the higher end. A metre [3.2 feet] is now a middle-of-the-road estimate. In the previous IPCC report [released in October, 2014], it was the high end. 

One thing that has changed is that not only are the sea levels rising but our estimates of how fast it will rise are also rising. In other words, science changes and it only seems to get worse as science changes--partly because people are conservative and new facts tend to go in the opposite way of conservatism. 

There is uncertainty about the rate of sea-level rise and also it depends on the time frame. It is one of the last things to happen. After you emit the carbon, it takes a while for the temperature rise to happen because the oceans soak up all the heat. 

The sea-level rise takes even longer. So last time in geologic history that there was so much carbon in the atmosphere, the sea levels were much higher. Maybe 10 or 20 [feet].

So that’s probably where we are headed, but it takes a long time to get there. Whether it is 100 years or a 1,000 years to get to values so extreme which will put a lot of cities totally under water, we don’t know yet. It also depends on which city you are talking about. Mumbai is in big trouble, but New York not as much. Miami--I don’t know what they are going to do there because it is difficult to even build coastal walls there.

Miami real estate is still doing well and I do not understand it. Maybe it is still a rational decision to buy in Miami if you don’t plan on keeping it for your descendants. Things are definitely going to get worse in some cities like Mumbai within decades.

Well before these cities actually become uninhabitable because of regular inundation, at some point, the market forces will snap. In other words, it doesn’t have to be the case that the place is actually uninhabitable. It just has to have enough people to realise that it is going to become uninhabitable, that the value of real estate crashes, and then we will see a massive economic crisis. 

Coastal real estate in the US, I think in many regions, is probably doomed. The market forces are going to do it. I can’t tell you if that is going to happen 50 years from now or tomorrow, and it is going to be like the housing price crash.

Your team looked at the possibility of a cyclone making landfall in Mumbai. Could you elaborate on that study?

The one main takeaway is that a major cyclone landfall in Mumbai is possible, although it is not that likely in any given year since it has not happened in the modern history of the city. Since about the 1870s--that’s how far the IMD [India Meteorological Department] data goes back in its modern form--there has not been a catastrophic cyclone. 

If you get a really big cyclone making landfall at the wrong angle to Mumbai, then you can have serious storm surge and it could be bad.

The number one takeaway from our study is that it could happen. It has not happened in anyone’s memory, lifetime or even well-documented history, but it could happen.

There are other takeaways, because our study did not consider climate change at all. We could do that but because we didn’t have a system in place to do that, we did what we could do at that time--this quite a conservative estimate.

How climate change affects cyclone is a little bit different in different parts of the world. Most likely, it would probably shift a bit more towards the Arabian sea from the Bay of Bengal. So, the risk is probably a bit worse than our estimate. We couldn’t say that based on our own work but our reading of the literature suggests that.

All those low-lying areas along the Thane creek would be at risk. A lot of new development would be at risk.

Source: Earth Observatory, NASA 
The North Indian basin where Arabian sea is one of the least active regions for cyclones in the northern hemisphere and sees on an average 4.8 storms every year.

What does this mean for our policymakers?

The first one is easy to say, but not to do. The city should have an emergency management plan in place in case there is a serious cyclone. As of now, they do not have one. I have read the Mumbai emergency management plans and the Maharashtra one that was written after the 2005 floods [which saw over 1,000 people die as the city received record rainfall], when they started some new efforts. They do not seriously account for risk of a major cyclone. That is probably because it has not happened.

They have a little bit about the cyclone where they say we will evacuate the fishermen in case of a major event, but it does not reckon on the chance of a cyclone. I don’t know what you would do if you have millions of people in low-lying areas at risk, how do you evacuate them in Mumbai.

It is a question of the transit system. You’ve got a couple of roads and then some flyovers, and you will have everybody trying to squeeze in those roads. If you have to evacuate people from the south, how are you going to do it? The trains are already full, you can’t put any more people on those trains. You have maybe a couple of days of warning. IMD can forecast pretty good, just as good as we can.

So, you might have 3-5 days when you might know that there is some risk and 1-2 days ahead of time, you might know you are really in trouble. It is some time, but it is not a lot of time. If you have thought it through ahead of time, then you will make better decisions than if you have not. The city is what it is, it is a challenging environment to know how to deal with it if this were to really happen. But sure, you will do a better job if you have thought ahead of the time.

The forecast will be better because cyclones are more predictable compared to the extreme rain events that cause these floods.

Developing these low-lying areas comes at a huge risk and you just have to be aware of that. I know there is tremendous pressure for the city to develop and there are tons of people and jobs to think of, there is money so you want to have more transportation, better airports and ports, but you are building on very risky places.

I don’t know how to do the cost-benefit calculation. I don’t know what the alternatives are. Not to mention these are environmentally desirable regions--these mangroves and wetlands--and many of the environmental groups are furious. 

You have addressed the U.S. Congress on climate change, but many scientists feel that it is not their job to communicate. From the perspective of speaking to policymakers and how that pushes change, what advice would you give to scientists--especially those in the developing countries where there isn’t a lot of funding for science and there might be a handful of research that focuses on the region? 

I don’t think scientists are the most effective advocates. I think we should be advocates. I disagree with people who think we have no responsibility there, I think we do. At the same time, it has been a historic mistake that people [civil society] think we can be advocates of climate policy in this country [US] because we have not been that effective.

In part because we didn’t realise for generations that it wasn’t a part of science communication, but it is a political street-fight and we are up against a denial movement here, we are not well prepared for that.

We have ways to express ourselves that are very guarded, well prepared and nuanced. That doesn’t work well when your opponent is willing to say anything to win the argument. It is like bringing a pencil to a gunfight.

And the other thing is, I speak from a privileged position and I don’t want to be lecturing my Indian colleagues on how they should behave. That said, it would be good for India if the scientists could learn to be a little more vocal. Not only because of how they would influence policy but also in how they might attract a few more young people in science. Young people are not thinking about doing basic research. 

If the best scientists in India were appearing in the newspapers frequently, that might get a few more good students into the science programmes as well.

That said, some are better at it than the others. I think many people don’t do it because they think their work will be misrepresented and there are political tensions.

Also, the way the journalist translates your information will never be like it is in your scientific paper because they can’t use the same words. You have to get over it.

The wrong question to ask is did they [journalists] get everything right. The right question is whether the article is better or worse if they didn’t talk to me. In other words, you shouldn’t be comparing it to your scientific paper but to an uneducated journalist who didn’t get any help from the scientist. That’s the way to look at it.

(Shetty is a reporting fellow with IndiaSpend.)

We welcome feedback. Please write to respond@indiaspend.org. We reserve the right to edit responses for language and grammar.

New York/Bengaluru: In 2015, India-born author Amitav Ghosh, researching his latest book, wrote to Adam Sobel, an atmospheric scientist at Columbia University in New York. Sobel, 52, studies extreme weather and climate. Could Mumbai be hit by a cyclone, Ghosh asked Sobel. 

In his book ‘The Great Derangement: Climate Change and the Unthinkable’, Ghosh looks at coastal cities around the world, questioning why they were built with scant regard to extreme weather events such as cyclones. One of his main arguments is that colonisation disregarded local knowledge of weather.

Ghosh then asked Sobel to provide a scientific answer: Was Mumbai built the way it was because the odds of cyclonic storms were virtually nil in the Arabian Sea? Sobel decided to conduct a study. Yes, Mumbai could be hit by a cyclone but the probability of that happening in any given year is slim, his team of researchers found. They did not, however, look at the changes in storm patterns due to climate change. 

Global warming has led to changes in ocean temperatures, including in the Arabian Sea, causing both sea-level rise and changes in rainfall over India. With this, the possibility of a cyclone making landfall along India’s western coastline is inching up, a September 2019 report from the Intergovernmental Panel for Climate Change (IPCC)--the United Nations’ body set up to assess science related to climate change--said.

India’s west coast sees less cyclonic activity than the eastern coast along the Bay of Bengal. Of all the cyclones that develop in the Bay of Bengal, over 58% hit the east coast and beyond, while 25% of the cyclones that develop in the Arabian Sea reach the west coast, according to government data. Of those in the Arabian Sea, most head northwards, towards Gujarat, and take place in October and November.

Nearly 5,700 km of India’s 7,500-km long coastline is highly vulnerable to tropical cyclones, according to government data. Some 320 million Indians--or a quarter of the country’s population--are vulnerable to cyclone-related hazards.

A few weeks ago, around the time when world leaders were debating climate action at the UN, IndiaSpend caught up with Sobel at his office in Columbia University. In an interview, Sobel spoke about the latest science on extreme weather events and touched on how coastal real estate prices around the world have begun to respond to what scientific evidence says: Living close to the coast is not a good idea, with sea levels and the frequency of extreme weather events going up. 

Edited excerpts from the interview:

In The Great Derangement, Amitav Ghosh looks at climate change through the lens of stories, history and politics, and elaborates on how local knowledge of the weather and climate was disregarded when a lot of the colonial cities were built. Looking at cities such as New York and Mumbai through the lens of science, do you find merit in that argument? 

That point that Amitav makes in The Great Derangement is one of the most profound ones. It gave me a new understanding of the issue in terms of an appreciation of the historical context.

Climate scientists like me, we talk a lot about sea-level rise. We worry a lot about sea-level rise because it is clearly going to be one of the biggest, the most egregious and obvious ways that climate change will affect people. We have so many people living on low coastlines. Eventually, some of those [cities] are going to be permanently under water, but long before that happens, they are going to be inundated more regularly by extreme events--whether it be storms that in the past wouldn’t have caused so much flooding because the sea levels started lower and so the storm surge didn’t have as much impact, or even just tides.

We talk a lot about how coastal cities are at risk and that’s probably because a huge number of people live in coastal cities--there is a lot of valuable real estate, a lot of valuable economic activity in coastal cities. 

What cities are most vulnerable differs whether we are worried about people or dollars. New York, Shanghai, Mumbai, Kolkata: these are the places. What Amitav pointed out, which I hadn’t appreciated before, was that these are all colonial cities built roughly around the same time in history. 

Before that, if you look at the older cities, they are inland, like Paris and London are. Or Beijing, for instance.

So, the empire [British] felt that being on the coastal cities is strategically valuable. The argument was that people who lived in these places for a long time had some kind of respect for the sea, understanding that it was dangerous.

In Mumbai, before the British, they were just a bunch of islands. A couple of them had hills but mostly they were very flat. All this stuff now that’s being developed along Thane creek where they are putting the new airport, that is all very low marshy stuff. Why? Because that’s the only thing that is left. And there is a reason for that. Similarly, if you look at where the slums are, Dharavi for instance, they are basically the old river beds. You can go to Dharavi and see the old customs house. Somebody would have to point it out to you or you wouldn’t know it. It is the 19th century customs house. What a customs house means is that you would come up on a boat in a river and you would pay a tax. And now, there is no river there.

Coastal real estate is really valuable, so you have the richest people on the coast--like in Marine Drive--but it is also kind of the worst. It is risky and marginal land that is not completely stable and safe to build on.

You can build on it and you might be fine for a while, or you might not. 

What kind of future are these cities staring at and how long into the future is it?

It is hard to answer that with precision. The rate of sea-level rise is uncertain. We use [the year] 2100 as a benchmark for no particularly good reason but just to pick some benchmark which is in common use. The estimates of global sea-level rise for 2100 compared to pre-industrial time are between 1-2 feet at the low end and 6 [feet] on the higher end. A metre [3.2 feet] is now a middle-of-the-road estimate. In the previous IPCC report [released in October, 2014], it was the high end. 

One thing that has changed is that not only are the sea levels rising but our estimates of how fast it will rise are also rising. In other words, science changes and it only seems to get worse as science changes--partly because people are conservative and new facts tend to go in the opposite way of conservatism. 

There is uncertainty about the rate of sea-level rise and also it depends on the time frame. It is one of the last things to happen. After you emit the carbon, it takes a while for the temperature rise to happen because the oceans soak up all the heat. 

The sea-level rise takes even longer. So last time in geologic history that there was so much carbon in the atmosphere, the sea levels were much higher. Maybe 10 or 20 [feet].

So that’s probably where we are headed, but it takes a long time to get there. Whether it is 100 years or a 1,000 years to get to values so extreme which will put a lot of cities totally under water, we don’t know yet. It also depends on which city you are talking about. Mumbai is in big trouble, but New York not as much. Miami--I don’t know what they are going to do there because it is difficult to even build coastal walls there.

Miami real estate is still doing well and I do not understand it. Maybe it is still a rational decision to buy in Miami if you don’t plan on keeping it for your descendants. Things are definitely going to get worse in some cities like Mumbai within decades.

Well before these cities actually become uninhabitable because of regular inundation, at some point, the market forces will snap. In other words, it doesn’t have to be the case that the place is actually uninhabitable. It just has to have enough people to realise that it is going to become uninhabitable, that the value of real estate crashes, and then we will see a massive economic crisis. 

Coastal real estate in the US, I think in many regions, is probably doomed. The market forces are going to do it. I can’t tell you if that is going to happen 50 years from now or tomorrow, and it is going to be like the housing price crash.

Your team looked at the possibility of a cyclone making landfall in Mumbai. Could you elaborate on that study?

The one main takeaway is that a major cyclone landfall in Mumbai is possible, although it is not that likely in any given year since it has not happened in the modern history of the city. Since about the 1870s--that’s how far the IMD [India Meteorological Department] data goes back in its modern form--there has not been a catastrophic cyclone. 

If you get a really big cyclone making landfall at the wrong angle to Mumbai, then you can have serious storm surge and it could be bad.

The number one takeaway from our study is that it could happen. It has not happened in anyone’s memory, lifetime or even well-documented history, but it could happen.

There are other takeaways, because our study did not consider climate change at all. We could do that but because we didn’t have a system in place to do that, we did what we could do at that time--this quite a conservative estimate.

How climate change affects cyclone is a little bit different in different parts of the world. Most likely, it would probably shift a bit more towards the Arabian sea from the Bay of Bengal. So, the risk is probably a bit worse than our estimate. We couldn’t say that based on our own work but our reading of the literature suggests that.

All those low-lying areas along the Thane creek would be at risk. A lot of new development would be at risk.

Source: Earth Observatory, NASA 
The North Indian basin where Arabian sea is one of the least active regions for cyclones in the northern hemisphere and sees on an average 4.8 storms every year.

What does this mean for our policymakers?

The first one is easy to say, but not to do. The city should have an emergency management plan in place in case there is a serious cyclone. As of now, they do not have one. I have read the Mumbai emergency management plans and the Maharashtra one that was written after the 2005 floods [which saw over 1,000 people die as the city received record rainfall], when they started some new efforts. They do not seriously account for risk of a major cyclone. That is probably because it has not happened.

They have a little bit about the cyclone where they say we will evacuate the fishermen in case of a major event, but it does not reckon on the chance of a cyclone. I don’t know what you would do if you have millions of people in low-lying areas at risk, how do you evacuate them in Mumbai.

It is a question of the transit system. You’ve got a couple of roads and then some flyovers, and you will have everybody trying to squeeze in those roads. If you have to evacuate people from the south, how are you going to do it? The trains are already full, you can’t put any more people on those trains. You have maybe a couple of days of warning. IMD can forecast pretty good, just as good as we can.

So, you might have 3-5 days when you might know that there is some risk and 1-2 days ahead of time, you might know you are really in trouble. It is some time, but it is not a lot of time. If you have thought it through ahead of time, then you will make better decisions than if you have not. The city is what it is, it is a challenging environment to know how to deal with it if this were to really happen. But sure, you will do a better job if you have thought ahead of the time.

The forecast will be better because cyclones are more predictable compared to the extreme rain events that cause these floods.

Developing these low-lying areas comes at a huge risk and you just have to be aware of that. I know there is tremendous pressure for the city to develop and there are tons of people and jobs to think of, there is money so you want to have more transportation, better airports and ports, but you are building on very risky places.

I don’t know how to do the cost-benefit calculation. I don’t know what the alternatives are. Not to mention these are environmentally desirable regions--these mangroves and wetlands--and many of the environmental groups are furious. 

You have addressed the U.S. Congress on climate change, but many scientists feel that it is not their job to communicate. From the perspective of speaking to policymakers and how that pushes change, what advice would you give to scientists--especially those in the developing countries where there isn’t a lot of funding for science and there might be a handful of research that focuses on the region? 

I don’t think scientists are the most effective advocates. I think we should be advocates. I disagree with people who think we have no responsibility there, I think we do. At the same time, it has been a historic mistake that people [civil society] think we can be advocates of climate policy in this country [US] because we have not been that effective.

In part because we didn’t realise for generations that it wasn’t a part of science communication, but it is a political street-fight and we are up against a denial movement here, we are not well prepared for that.

We have ways to express ourselves that are very guarded, well prepared and nuanced. That doesn’t work well when your opponent is willing to say anything to win the argument. It is like bringing a pencil to a gunfight.

And the other thing is, I speak from a privileged position and I don’t want to be lecturing my Indian colleagues on how they should behave. That said, it would be good for India if the scientists could learn to be a little more vocal. Not only because of how they would influence policy but also in how they might attract a few more young people in science. Young people are not thinking about doing basic research. 

If the best scientists in India were appearing in the newspapers frequently, that might get a few more good students into the science programmes as well.

That said, some are better at it than the others. I think many people don’t do it because they think their work will be misrepresented and there are political tensions.

Also, the way the journalist translates your information will never be like it is in your scientific paper because they can’t use the same words. You have to get over it.

The wrong question to ask is did they [journalists] get everything right. The right question is whether the article is better or worse if they didn’t talk to me. In other words, you shouldn’t be comparing it to your scientific paper but to an uneducated journalist who didn’t get any help from the scientist. That’s the way to look at it.

(Shetty is a reporting fellow with IndiaSpend.)

We welcome feedback. Please write to respond@indiaspend.org. We reserve the right to edit responses for language and grammar.


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