Desk Report
Publish: 12 Oct 2021, 05:25 pm
Sea level rise || Representational Image || Photo; Collected
Even if humanity beats the odds and caps global warming at
1.5 degrees Celsius above preindustrial levels, seas will rise for centuries to
come and swamp cities currently home to half-a-billion people, researchers
warned Tuesday.
In a world that heats up another half-degree above that
benchmark, an additional 200 million of
today's urban dwellers would regularly find themselves knee-deep in seawater and more vulnerable to devastating
storm surges, they reported in Environmental Research Letters.
The worst-hit in any scenario will be Asia, which accounts for
nine of the ten mega-cities at the highest risk.
Land home to more than half the populations of Bangladesh
and Vietnam fall below the long-term high tide line, even in a 2C world.
Built-up areas in China, India and Indonesia would also face
devastation.
Most projections for sea-level rise and the threat it poses
to shoreline cities run to the end of the century and range from half a metre to less than twice that, depending on how quickly carbon pollution is reduced.
But oceans will continue to swell for hundreds of years
beyond 2100 -- fed by melting ice sheets, heat trapped in the ocean and the
dynamics of warming water -- no matter how aggressively greenhouse gas
emissions are drawn down, the findings show.
Not 'if' but 'when'
"Roughly five per cent of the world's population today
live on land below where the high tide level is expected to rise based on
carbon dioxide that human activity has already added to the atmosphere,"
lead author Ben Strauss, CEO and chief scientist of Climate Central, told AFP.
Today's concentration of CO2 -- which lingers for hundreds
of years -- is 50 per cent higher than in 1800, and Earth's average surface temperature
has already risen 1.1C. That's enough to eventually push up sea levels nearly
two metres (more than six feet), whether it takes two centuries or 10, Strauss
said.
The 1.5-C 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."
Buying time
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 3-C 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.
Subscribe Shampratik Deshkal Youtube Channel
Topic : Global Warming Sea level rise
© 2024 Shampratik Deshkal All Rights Reserved. Design & Developed By Root Soft Bangladesh