Scientists predict ‘catastrophic’ consequences of sea level rise over two metres

Scientists predict 'catastrophic' consequences of sea level rise over two metresGlobal sea levels could rise in excess of two metres – causing catastrophic consequences for the world, according to a team of international scientists.

Such a rise could result in the loss of 1.79 million km2 of land, including critical regions of food production, and potential displacement of up to 187 million people.

Traditional methods for predicting rising sea levels from the melting ice sheets in Greenland and the Antarctic are based on numerical modelling.

Such projections remain challenging due to ongoing uncertainty regarding the evolution of the Greenland and Antarctic ice sheets, particularly in response to climate change.

A team of international scientists used a technique called structured expert judgment to ask 22 ice sheet experts to estimate plausible ranges for future sea level rises.

They asked them to consider the projected melting of each of the Greenland, West Antarctic and East Antarctic ice sheets under low and high future global temperature rise scenarios.

Lead author professor Jonathan Bamber, from the University of Bristol, said: "Structured expert judgment provides a formal approach for estimating uncertain quantities based on current scientific understanding, and can be useful for estimating quantities that are difficult to model.

"Projections of total global subsequent sea level rise using this method yielded a small but meaningful probability of subsequent sea level rise exceeding two metres by the year 2100 under the high temperature scenario, roughly equivalent to 'business as usual', well above the 'likely' upper limit presented in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change."

The findings suggest that coastal communities should not rule out the possibility of 21st century subsequent sea level rise in excess of two metres when developing adaptation strategies.

Prof Bamber added: "Such a rise in global sea level could result in land loss of 1.79 million km2, including critical regions of food production, and potential displacement of up to 187 million people.

"A subsequent sea level rise of this magnitude would clearly have profound consequences for humanity."

The structured expert judgment process provided an opportunity for experts to discuss their scientific rationales for the quantitative judgments they make on uncertainties relating to future ice sheet contributions to sea level.

This approach also served to identify some poorly understood but potentially critical processes, such as "marine ice cliff instability", which may act in future as significant tipping points in ice sheet response to temperature rise.

– The study is published in the journal Proceedings of the National Academy of Sciences of the United States of America.

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