From the Times of India: Historically, biggest disasters are ones that are rare, says scientist Adam Sobel

Historically, biggest disasters are ones that are rare, says scientist Adam Sobel

From the Times of India

Adam Sobel, director and chief scientist of Columbia University’s Initiative on Extreme Weather and Climate, was boarding a plane from New York last Monday when he heard the forecast: Cyclone Ockhi was heading to Mumbai too. Fortunately, the cyclone weakened as it progressed. But the moment was still eerie—for Sobel and his team, including Zachary Burt, are studying the likelihood and potential impact of a cyclone hitting Mumbai, something that has not happened in recent history. Sobel, who will give a lecture on Tuesday at the city’s Columbia Global Centre, spoke to TOI:

On the current cyclone risk for Mumbai: Estimates of cyclone risk both from our model and from [the MIT model] tell us that in the historical climate, a major cyclone landfall in Mumbai, that is strong enough to generate a significant storm surge, is at least a several-hundred-year-event. That means the probability in a single year is a fraction of a percent. But if you look at Sandy, that was also a couple-of-hundred-years event for New York. The similarity with New York is quite spooky. There are one or two cyclones a year in the Arabian Sea, but they tend to go west to the Arabian peninsula or north to Gujarat.

Gujarat has had several landfalls in the last 20 yearsbut they never make that right turn to Mumbai. The same thing was true in the Atlantic, the hurricanes never took a left turn to New York until Sandy. Ockhi did take that right turn last week but weakened before landfall.

On the city’s vulnerability: Vulnerability is high as the city is flat, it’s right by the sea, it has huge populations at low elevations, and high-value real estate. Flooding events like in 2005 have demonstrated the vulnerability… Historically, the biggest disasters are the ones that are sufficiently rare that the place develops without worrying about it. But then it happens. If it was a common occurrence, the city would have developed differently.

On the lessons from Hurricane Sandy: The biggest single message would be that while Mumbai has many issues, and some events are more probable than others, it is not that unreasonable to think about emergency management planning. New York had reports going back at least 20 years on what an event [like Sandy] would look like, where the water would come in, because as in Mumbai, storm surge is more important than winds. They knew to shut the subways ahead of time because they would flood, and where to evacuate people from and how long it would take. All the hard-hit areas in New York were former wetlands, barrier islands, and landfill (reclamation), of which there is more in Mumbai.

On post-Sandy measures: There have been lots of measures, and a lot of federal money coming in, for flood-proofing like flood walls, elevations, barriers. A couple of places in Staten Island that were built on wetlands and were washed out during Sandy are being restored to wetlandsthe state is buying residents out. But that’s the exception. By and large the areas hardest hit are not being abandoned, they are being redeveloped. In some cases, in smarter ways by elevating the house or not putting utilities in basements. Many scientists think we would be better off if there was a managed retreat [from the coastline]. But that’s hard to do. Politically and economically, the waterfront is valuable. And some people don’t want to move out.

Global warming increasing cyclones in Arabian Sea

* Global warming has increased the probability of cyclonic storms in the Arabian Sea in the post-monsoon period, according to a recent study published in ‘Nature Climate Change’

* Scientists led by Hiroyuki Murakami of Princeton University used advanced climate models to look at conditions in the pre-industrial period and more recently

* They found that anthropogenic global warming had increased cyclonic storms in the region, and would likely continue to do so

* Warming was one of the major contributors to storms in 2014 and 2015, the study found

* Cyclone Nilofar caused flash floods in Oman in 2014, while Cyclone Chapala and Megh made landfall in Yemen in 2015

* Murakami and others had earlier predicted a 46% rise in cyclones in the Arabian Sea, and a 31% decline in the Bay of Bengal

* Historically, the Arabian Sea has seen fewer cyclones than the Bay of Bengal