When global warming stops, seas will still rise, warn researchers – CNA
The 1.5C warming limit enshrined in the Paris Agreement that nations will try to keep in play at the COP26 climate summit in Glasgow next month translates into nearly three metres over the long haul.
Unless engineers figure out how to quickly remove massive amounts of CO2 from the atmosphere, that amount of sea level rise is not a matter of “if” but “when”, according to the study.
These are the optimistic scenarios.
“The headline finding for me is the stark difference between a 1.5C world after sharp pollution cuts versus a world after 3C or 4C of warming,” Strauss said.
“At Glasgow and for the rest of this decade, we have the chance to help or to betray a hundred generations to come.”
National carbon-cutting pledges under the 2015 Paris treaty would, if honoured, still see Earth warm 2.7C by 2100. If efforts to reign in greenhouse gases falter, temperatures could rise 4C or more above mid-19th century levels.
This much warming would add six to nine metres to global oceans over the long haul, and force cities currently home to nearly a billion people to either mount massive defences against future sea level rise or rebuild on higher ground.
In China alone, land occupied today by 200 million people would fall below high tide in a 3C scenario. And the threat is not only long-term: absent massive sea walls, Chinese cityscapes home to tens of millions could become unliveable within 80 years.
“1.5C of warming will still lead to devastating sea level rise, but the hotter alternatives are far worse,” said Strauss.
“We’re in bad shape but it is never too late to do better, and the difference we could make is enormous.”
At higher levels of warming, the danger increases substantially of triggering the irreversible disintegration of ice sheets or the release of natural stores of CO2 and methane in permafrost, scientists warn.
Capping global warming as low as possible also buys us time to adapt.
“It is almost certain that seas will rise more slowly in a 1.5C or 2C warmer world,” Strauss said.
Researchers from Princeton University and the Potsdam Institute for Climate Impact Research in Germany contributed to the study.