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Oct 2019

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Sea level increase by 2100 may be double the present estimate

Source: Asia Insurance Review | Jul 2019

International scientists led by the University of Bristol, UK, have had a relook at the Intergovernmental Panel on Climate Change (IPCC) estimates on how much the world’s oceans are likely to rise during this century.
 
Many climate scientists have said that the IPCC estimates about the rise in sea levels in this century, which were a part of the IPCC report published in 2013, were a conservative estimate. They say there is a possibility that the eventual figure could be around double the forecast, threatening hundreds of millions of people with having to abandon their homes.
 
The IPCC report had said, “The continued warming of the Earth, if there are no major reductions in greenhouse gas emission, would see the seas rising between 52cm and 98cm by 2100.”
 
The current study conducted by University of Bristol has been published in a recent issue of the Proceedings of the National Academy of Sciences (PNAS).
 
The oceans could rise by around two meters by 2100
University of Bristol professor and lead author of the study Professor Jonathan Bamber said, “In an extreme case, the sea level rise over the next 80 years could mean that by 2100 the oceans will have risen by around six feet (two metres) − roughly twice the level thought likely till now, with pretty unimaginable consequences.”
 
If emissions continue on their current path, the business-as-usual scenario, the researchers say, then the world’s seas would be very likely to rise by between 62 cm and 238 cm by 2100. This would be in a world that had warmed by around 5 °C, one of the worst-case scenarios for global warming.
 
Critical regions of food production could be lost
“For 2100, the ice sheet contribution is very likely in the range of 7–178cm but once you add in glaciers and ice caps outside the ice sheets and thermal expansion of the seas, you tip well over two metres,” said Professor Bamber.
 
He said, “Such a rise in global sea level could result in land loss of 1.79m sq. km, including critical regions of food production, and potential displacement of up to 187m people.”
 
It is small but statistically significant probability
Professor Bamber said, “When you start to look at these lower-likelihood but still plausible values, then the experts believe that there is a small but statistically significant probability that West Antarctica will transition to a very unstable state, and parts of East Antarctica will start contributing as well.”
 
The chances of sea level rise as devastating as this are small, the Bristol team say − about 5%. But they should be taken seriously.
 
Used a different methodology for their research
The Bristol team used a different way of trying to gauge the possible effect of the way the ice is melting in Greenland, West and East Antarctica, not relying simply on projections from numerical models.
 
Their method used a technique called a structured expert judgement study, which involved 22 ice sheet experts in estimating plausible ranges for future sea level rise caused by the projected melting of the ice sheets in each of the three areas studied, under low and high future global temperature rise scenarios. A 
 
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