Failure to Meet Paris Accord Goals Will Lead to ‘Irreversible’ Sea-Level Rise, Scientists Warn

Using a first-ever physics-based model of Antarctic ice sheets, researchers found sea levels will rapidly increase beyond control by the end of the century if greenhouse gas emissions aren’t sufficiently curbed.

In understanding the impact of climate change on sea-level rise, Greenland’s Helheim Glacier is a possible analog for the future behavior of the much larger glaciers on Antarctica. (Photo courtesy of Knut Christianson)

(CN) — Researchers testing a set of Paris climate accord targets with Antarctic ice models made an alarming discovery: unchecked global warming could push sea levels past a tipping point in just 40 years.

After that, an irreversible, multigenerational surge would accelerate — and inundate. 

Under the Paris accord, nations agree to cut greenhouse gas emissions on a scale that would stem global warming to 3.6 degrees Fahrenheit above pre-industrial temperatures.

The accord also includes proposals or pledges for wholesale adoption of renewable energy systems and other policy changes that could lead to net-zero emissions and bring warming to just 2.7 degrees Fahrenheit above pre-industrial temperatures by the end of the century.

The pledge six years ago by more than 190 nations including the United States could prevent the worst effects of climate change, including catastrophic collapse of ecosystems and heavy damage to cities around the world.

Current greenhouse gas emission-tracking models show us, however, that global warming is on pace to exceed an increase of 5.4 degrees — far above even the basic threshold of the Paris climate agreement.

University of Massachusetts Amherst researchers aimed to test the impact of various global warming scenarios — based on Paris accord climate targets — on ice loss in the Antarctic region and the subsequent rise in sea-levels.

The Antarctic ice sheet — the planet’s largest reservoir of land ice — is a reliably sensitive indicator of global climate shifts and is already losing ice at a terrifyingly rapid pace.

The study, published Wednesday in the journal Nature, is the first to test whether nations’ successful or failed implementations of Paris accord climate targets would stem or accelerate the loss of land ice in the Antarctic region.

Lead researcher Rob DeConto of UMA and his colleagues tested three scenarios: warming at 2.7 degrees, 3.6 degrees and 5.4 degrees Fahrenheit, respectively.

If nations meet the 2.7 or 3.6 degree warming limit targets, Antarctic ice loss would transfer between 2.4 and 4.3 inches of ice water into the oceans by 2100, according to the study published Wednesday in the journal Nature.

But if the current pace holds and global climate reaches or exceeds a 5.4-degree increase, the Antarctic region would see a huge spike in ice loss. 

Without immediate, large-scale policy changes, scientific interventions including geoengineering would be ineffective at stopping a nearly 7 to 8-inch deposit of Antarctic ice melt into the oceans by 2100, the study found.

“More fossil-fuel-intensive scenarios result in even greater acceleration,” the study authors wrote. “Ice-sheet retreat initiated by the thinning and loss of buttressing ice shelves continues for centuries, regardless of bedrock and sea-level feedback mechanisms or geoengineered carbon dioxide reduction. These results demonstrate the possibility that rapid and unstoppable sea-level rise from Antarctica will be triggered if Paris Agreement targets are exceeded.”

The findings show that unchecked greenhouse gas emissions would push sea-level rise beyond a tipping point by 2060 and into an irreversible slide toward sustained sea-level increase.

“These results demonstrate that current policies allowing +3 degrees Celsius or more of future warming could exceed a threshold, triggering extensive thinning and loss of vulnerable Antarctic ice shelves and ensuing marine ice instabilities starting within this century,” researchers wrote in the study. “Resulting ice loss would be irreversible on multi-century timescales, even if atmospheric temperatures return to preindustrial-like values.”

Looking at longer timescales, researchers found that Antarctica could contribute 3.3 feet of sea level rise by 2300 under a 3.6 degrees or less warming scenario within the Paris accord targets.

Under extreme warming scenarios with no cap on emissions, sea-levels could see catastrophic increases of 33 feet or more by 2300, the study found. 

DeConto said in a statement released with the study that allowing extensive Antarctic ice loss would trigger another massive deposit of ice water into the ocean.

“If the world continues to warm, the huge glaciers on Antarctica might begin behaving like their smaller counterparts on Greenland, which would be disastrous in terms of sea level rise,” DeConto said.

Researchers did not immediately respond to a request for further comment on the study.

The study was supported by funding from the National Science Foundation and the NASA Sea Level Change Science Team.

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