According to new research just published sea levels could rise nearly twice as much as previously predicted by the end of this century, if carbon dioxide emissions continue unabated, an outcome that could devastate coastal communities around the globe.
The world’s coastal cities have been warned to prepare for the possibility of a sea level rise exceeding two metres by the end of the century, with “profound consequences for humanity.”
A new assessment found runaway carbon emissions and melting ice sheets could result in such a worst case scenario, potentially double the upper limit outlined by the United Nations climate science panel’s last major report.
The startling findings, published in the Proceedings of the National Academy of Sciences (PNAS), paint a far grimmer picture than current consensus predictions, which have suggested that seas could rise by just under a meter at most by the year 2100.
Such big sea level rises so soon would lead to nightmarish impacts, said Professor Jonathan Bamber of the University of Bristol.
“If we see something like that in the next 80 years we are looking at social breakdown on scales that are pretty unimaginable.”
Around 1.79 million square kilometres of land could be lost and up to 187 million people displaced.
“Many small island states, particularly those in the Pacific, will effectively be pretty much inhabitable. We are talking about an existential threat to nation states,” said Professor Bamber.
His team came to their conclusions after taking evidence from 22 leading researchers on how the Greenland and Antarctic ice sheets might respond to future climate change.
Aggregating the responses revealed a one in twenty chance that seas could rise by more than two metres by 2100 if unchecked carbon emissions lead to average global warming of five degrees Celsius, about 2.0°C more than the temperature rises current government pledges would lead to.
“It’s unlikely but it’s plausible. We are talking about a five per cent probability,” said Professor Bamber, of how the ice would react to such extreme warming.
The UN’s Intergovernmental Panel on Climate Change report said in 2013 that the worst case for sea level rise was 98 centimetres by 2100, plus potentially a few tenths of a metre extra from Antarctica if it began collapsing this century.
Professor Bamber said the IPCC was missing possible serious impacts by not looking at plausible but low probability increases.
One factor influencing assessments is that relatively new satellite measurements are showing ice mass loss happening faster than models expected.
Another key issue is the idea that ice cliffs in Antarctica could collapse under their own weight after buttressing ice sheets supporting them are melted by climate change.
The risk of a disastrous two-metre sea level rise could still be avoided if emissions were cut quickly enough, said Professor Bamber.
“We can make some choices but we have to make them very soon.”
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