Agence France-PresseMay 7, 2021 10:45:54 AMT
Limiting global warming to 1.5 degrees Celsius could halve sea level rise due to the melting of icebergs in this century, according to a new major study that models how the Earth’s frozen states respond to ever-increasing greenhouse gas emissions. Since 1993, melting ice has affected at least half of the world’s sea level rise, and scientists have previously warned that the vast ice sheets in Antarctica would disappear faster than the worst chances.
An international team of more than 50 climate scientists combined hundreds of molten simulations of Antarctic and Greenland ice sheets containing enough frozen water to lift the world’s seas by about 65 meters (213 feet).
They also included molten modeling of the Earth’s more than 220,000 glaciers, which make up only one percent of the ice on Earth but cause up to a fifth of sea level rise.
The group analyzes the models to obtain probability estimates of how much melting ice would lift the oceans on multiple discharge routes.
They found that if humanity successfully limits warming to 1.5 ° C – the target set by the Paris Climate Agreement – it could halve the impact of ice on sea level rise by 2100.
This is compared to a warming planet of approximately 3 ° C if the countries’ current emission reduction promises were met.
“Global sea levels continue to rise,” said Tamsin Edwards, lead researcher at London’s King’s College Geographical Department.
“But we can halve the impact of ice melting if we limit warming to 1.5 degrees C relative to current promises.”
Uncertainty in Antarctica
A study published in the journal Nature found that the average effect on sea level rise at 1.5 ° C of melted ice by 2100 was 13 centimeters (five inches) compared to the currently projected 25 centimeters.
The analysis showed that the sea level rise caused by the Greenland ice sheet would fall by 70% if the 1.5-C target were reached, and the share of land-based glaciers would roughly halve.
However, the forecasts were less clear and varied widely in Antarctica.
Author Sophie Nowicki of NASA’s Goddard Airport said model uncertainty declined to a large extent to the extent that increased snowfall on a warming continent offset melting from ice racks.
“Greenland is really sensitive to changes in the atmosphere, so in a warmer world, you melt more on the surface of ice sheets,” Nowicki said.
“In Antarctica, it’s very complex. A warm world can mean more snowfall, but it can also mean more melt on the edge of the ice sheet.”
The calculations showed a 95 percent probability that the impact of Antarctica on sea level rise will be less than 56 centimeters by 2100.
But according to the “pessimistic scenario,” the study showed that Antarctica can lift global oceans even more, even if humanity manages to keep warming at 1.5 ° C.
Another study, also published Wednesday in Nature, found that limiting warming to 2 ° C above industrial levels is likely to maintain the current rate of ice melting in Antarctica.
However, if current emission reduction commitments are not strengthened by 2060, the models showed that the continent could add half a centimeter to sea level annually by 2100.
In addition, the study warned that if emissions continue at current levels, the peak will be reached around 2060, leading to the melting of Antarctica, which would be “irreversible over many centuries.”
A study led by a group from the University of Massachusetts Amherst modeled how ice shelves that prevent the Antarctic ice sheet from collapsing into the sea are likely to respond to temperature changes in this century.
With greater warming, the ice racks become thinner and more brittle, the models showed, compromising the accelerated melting and “calving” of the ice sheet, causing large pieces of ice to break into the sea, as has already happened in parts of the Arctic.
“Global warming above 2 ° C increases the risk of crossing the peak – where ice shelves thin or collapse, allowing for significant acceleration in ice loss and sea level rise,” said author Robert DeConto AFP. “When set in motion, ice retreat is unstoppable because sturdy ice racks don’t easily grow in a warming ocean.”