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Climate tipping points near for Greenland, but it’s not too late to save ice sheet, researchers say

Evan Bush
Wed, October 18, 2023

New research suggests the Greenland ice sheet is on track to cross a critical threshold that could cause runaway melting, but that it’s also possible the threshold will be crossed temporarily, cooling down the planet and ultimately returning the ice sheet to a stable state.

The findings, published Wednesday in the journal Nature, underscore the importance of limiting the planet’s warming to 1.5 degrees Celsius (about 2.7 Fahrenheit) — or returning to that level, or below, as quickly as possible if humanity exceeds it.

“If we change the temperature back fast enough, we don’t necessarily commit to a system change,” Nils Bochow, a climate scientist at the Arctic University of Norway in Tromsø and the lead author of the study, said in an interview. “We have time to reverse temperatures from this runaway effect.”


The Greenland ice sheet is one of more than a dozen theoretical climate tipping points — rapid, irreversible or abrupt changes — that keep some scientists up at night. And the findings, while alarming, add to a drumbeat refrain from many climate advocates: Urgency is essential, but it’s not too late to avoid the worst of climate change.


The research suggests the critical threshold for the Greenland ice sheet is between 1.7 and 2.3 degrees C of global warming. Bochow said humanity would have 100 years — perhaps more — to cool down and avoid locking in positive feedbacks that would intensify Greenland’s melting. He said that crossing the threshold, even temporarily, would likely cause several meters of sea level rise, but it would still be possible to stabilize the ice sheet.

Benjamin Keisling, an assistant research professor at the University of Texas Institute for Geophysics, who was not involved in the research, said the ice sheet’s size gives humanity a chance to shift course.

“These systems are really complex and because ice sheets like Greenland are so big, in some ways they’re sluggish to changes,” he said. “It’s not something you can melt over the course of a year or decade or century. That actually buys you some time.”

Scientists think the Greenland ice sheet, if melted completely, would contribute more than 7 meters (about 23 feet) of sea level rise to the world’s oceans. Melting a large portion of that ice sheet would reshape coastlines and societies in a process that would take hundreds or perhaps thousands of years.

World leaders are struggling to cut fossil fuels from their economies, and they remain off pace on goals to limit warming to levels considered safer and more tolerable during international climate negotiations. A 2022 U,N, report found the planet was on track to warm about 2.8 C above preindustrial times by 2100.

Under global leaders’ most ambitious aims, the world will emit enough greenhouse gases to raise temperatures above 1.5 degrees C above preindustrial times, before cooling and stabilizing around that mark.

This study describes, for the Greenland ice sheet, what researchers think could happen in an “overshoot” emissions scenario, in which humanity crosses a so-called tipping point but ultimately reins in greenhouse gases and cools the planet.

Twila Moon, the deputy lead scientist at National Snow and Ice Data Center in Colorado, said the findings were not surprising and reflected patterns observed by other researchers who have modeled the behavior of the Greenland ice sheet.

Moon, who was not involved in the study, said it did a nice job showing that “even if there’s a temperature offshoot, how quickly we can come back” and that climate action will remain meaningful even if world leaders miss their aims — a fate that looks increasingly realistic.

“This is a transition we must take, as humanity. And even if we don’t reach our most aspirational target, every tenth of a degree is really going to matter,” she said about reducing greenhouse gas emissions. “It’s valuable to be thinking about overshoot scenarios right now.”

The Greenland ice sheet is already on a prolonged path of decline. It has lost mass every year since 1998, Moon said. Over the past 20 years, it has lost the equivalent of 3.4 Olympic swimming pools of freshwater, on average, each second.

The ice sheet is losing mass as icebergs calve into the ocean and also because of summertime surface melt, which is a response to warmer air temperatures.

More than 20% of sea level rise documented by scientists since 2002 has been caused by ice sheet melt in Greenland, according to the Nature study. Greenland’s contribution to sea level rise will only grow as global average temperatures warm, Moon said. Sea level rise can cause coastal erosion, flooding and saltwater inundation of freshwater drinking systems, among other problems.

Action now will reduce the impact of sea level rise for future generations.

“Sea level rise for the next couple of decades is pretty baked into the system based on our past emissions. Where we see the influences of our actions today is in the 2060s, 2070s and beyond,” Moon said.

This article was originally published on NBCNews.com

Reversing warming may stop Greenland ice sheet collapse: study

AFP
Wed, October 18, 2023 

The melting of Greenland's vast ice sheet is estimated to have contributed more than 20 percent to observed sea level rise since 2002 (Kerem Yücel)

Breaching the global warming limits of the world's climate goals could see the melting of Greenland's ice sheet add more than a metre to rising sea levels, according to new research on Wednesday.

But the study by an international team of researchers found there would still be hope to prevent a collapse of the ice sheet -- if warming is reversed and brought back to the safer level.

The melting of Greenland's vast ice sheet -- the world's second-largest after Antarctica -- is estimated to have contributed more than 20 percent to observed sea level rise since 2002.

Rising sea levels threaten to intensify flooding in coastal and island communities that are home hundreds of millions of people, and could eventually submerge whole island nations and seafront cities.

A study published in the journal Nature on Wednesday used two models to simulate how Greenland's ice sheet would respond to future temperature increases over timescales ranging from hundreds to thousands of years.

Researchers suggested abrupt ice sheet losses would be triggered if global average temperatures reached a range of 1.7C-2.3C above pre-industrial levels.

That would risk a permanent "tipping point" that would see near-complete melting of the Greenland ice sheet over hundreds or thousands of years and could lift oceans by seven metres (23 feet), redrawing the world map.

But if the temperature increases were rolled back to the Paris deal 1.5C limit quickly enough -- by removing planet-heating pollution from the atmosphere using vast reforestation or technologies to capture carbon and permanently store it -- then the worst could be avoided.

"We found that the ice sheet reacts so slowly to human-made warming that reversing the current warming trend by cutting greenhouse gas emissions within centuries may prevent it from tipping," said study co-author Niklas Boers from the Potsdam Institute for Climate Impact Research.

"Yet, also just temporarily overshooting the temperature thresholds can still lead to a peak in sea level rise of more than a metre in our simulations."

- Tipping points breached -

Other tipping points in the Earth system may be breached far sooner, the researchers said, including rainforests and ocean current systems that change in much shorter timeframes.

"The Greenland ice sheet is likely more resistant to short-term warming" than previously thought, said Nils Bochow, a researcher at the Arctic University of Norway and lead author of the study.

But the researchers stressed that returning temperatures to below the "safe" threshold for the Greenland ice sheet would be far harder than keeping them below the limit in the first place.

World leaders will gather in Dubai from November 30 for crunch UN talks on slashing planet-warming greenhouse gas emissions, adapting to and financially bracing for the impacts of climate change.

Technologies to reduce temperatures on such a vast scale may not exist, Bochow told AFP.

"We should try everything today to keep the temperatures in a safe range rather than betting that we can reduce them later," he said.

Greenland's melting ice could ruin the Earth's coastal cities. A new study offers hope.

Doyle Rice, USA TODAY
Thu, October 19, 2023

There may be hope for the Greenland ice sheet after all.

In fact, according to a new study published Wednesday, the massive ice sheet is likely to be more resistant to global warming than had been thought before.

"We found that the ice sheet reacts so slowly to human-made warming that reversing the current warming trend by cutting greenhouse gas emissions within centuries may prevent it from tipping," said study co-author Niklas Boers from the Potsdam Institute for Climate Impact Research in Germany.

Nils Bochow, a researcher at the Arctic University of Norway and the lead author of the study, told NPR that "the Greenland ice sheet is more resilient than we thought."

But this doesn't mean we should forget about global warming: The study authors clearly state that the ice sheet's slow reaction doesn't imply that humanity should slow down in its fight against climate change.

What is the Greenland ice sheet?

The Greenland ice sheet covers about 80% of the world's largest island, and is 656,000 square miles – an area about three times the size of Texas, according to the National Snow and Ice Data Center. At its thickest point, the ice sheet measures almost 2 miles thick and contains about 696,000 cubic miles of ice.

If the entire Greenland ice sheet melted, global sea level would rise about 24 feet, the Center said. Such an amount would inundate coastal cities worldwide.

The ice sheet is estimated to have contributed more than 20% to the observed sea-level rise since 2002, as a result of melting due to rising temperatures, according to the journal Nature.

More: Greenland sees hottest temps in 1,000 years. How its melting ice sheet has major impact on sea level

What did the researchers discover?

Basically, "their work shows the worst-case scenario of ice sheet collapse and consequent sea-level rise can be avoided – and even partly reversed – if we manage to reduce the global temperatures projected for after 2100," said Bryn Hubbard, a professor of glaciology at Aberystwyth University in Wales.

"Moreover, the lower and sooner those temperatures fall, the more chance there is of minimizing that ice melt and sea-level rise," said Hubbard, writing in the Conversation.

Researchers used computer models to simulate what might happen to the ice sheet under various temperature scenarios in the decades and centuries to come. They found that that even if critical temperature thresholds are temporarily crossed, a possible tipping of the ice sheet and therefore drastic sea level rise over hundreds of thousands of years could still be prevented, the Potsdam institute said in a statement.

To make this happen, greenhouse gas emission reductions would have to occur as soon as possible following the future spike in temperature, so that the temperature can be stabilized at no more than 1.5 degrees Celsius above pre-industrial levels, in the long term.

”Our results underline that even if we do not manage to stay below 1.5 or 2 degrees (Celsius) of global warming within the coming decades, and temporarily cross the critical temperature threshold of the Greenland ice sheet, we still have a chance to act," said Bochow.

Timing, though, is critical, according to the study. If the return to cooler temperatures after an ‘overshoot’ of the threshold takes more than a few centuries, then the ice sheet will still likely contribute several meters to global sea-level rise.

More: Greenland was once actually green, study says. That's an ominous climate change scenario.

This article originally appeared on USA TODAY: Study on Greenland's ice sheet offers hope on global sea-level rise