Greenland Reaches Climate Tipping Point, But It's Not Too Late to Save the Ice Sheet, Say Researchers

Greenland Reaches Climate Tipping Point, But It's Not Too Late to Save the Ice Sheet, Say Researchers

Global warming could trigger runaway melting, raising sea levels, but efforts to limit emissions may still avert the worst climate scenarios.

A new study suggests that Greenland's ice sheet is on track to pass a critical threshold that could trigger runaway melting, but it's also possible that this threshold will be temporarily crossed, cooling the planet and ultimately stabilizing the ice sheet.

The results, published Wednesday in the journal Nature, underscore the importance of limiting the planet's warming to 1.5 degrees Celsius (about 2.7 degrees Fahrenheit) or returning to that level or lower as quickly as possible if humanity overshoots it.

"If we're changing the temperature back quickly enough, we don't necessarily have to commit to making changes to the system," said Niels Bohrs, a climate scientist at the Arctic University of Norway in Tromsø and the study's lead author. "We have time to revert it because of this runaway effect."

Greenland's ice sheet is one of over a dozen theoretical climate tipping points—rapid, irreversible, or abrupt changes—that keep some scientists up at night. And the findings, while troubling, add to the drumbeat of many climate advocates: Urgency is needed, but it's not too late to avoid the worst consequences of climate change.

The study posits that the critical threshold for Greenland's ice sheet lies between 1.7 and 2.3 degrees of global warming. Bohrs said humanity has about 100 years, and possibly more, to cool off and avoid locking in positive feedback loops that could amplify Greenland's melt. Crossing the threshold, even temporarily, is likely to lead to several meters of sea-level rise, but stabilizing the ice sheet would still be possible.

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

"These systems are really complex, and because ice sheets like Greenland are so large, they in some sense respond slowly to changes," he said. "It's not something that you can melt in a year, a decade, or even a century. It buys you a little bit of time."

Scientists estimate that if Greenland's ice sheet were to melt completely, it would raise global sea levels by more than 7 meters (about 23 feet). The melting of a significant portion of this ice sheet would alter coastlines and societies, and this process would take hundreds, possibly thousands of years.

World leaders are working hard to reduce fossil fuel use in their economies, but they still fall short of the temperature-limiting goals considered safer and more tolerable during international climate negotiations. According to a 2022 United Nations report, the planet is expected to warm by roughly 2.8°C above preindustrial levels by 2100.

Under the most ambitious targets set by world leaders, the world will emit enough greenhouse gases to push temperatures past 1.5 degrees Celsius compared to preindustrial times before cooling and stabilizing around that mark.

This study, concerning Greenland's ice sheet, describes what researchers believe could happen in an "overshoot" scenario where humanity crosses the tipping point but eventually reins in greenhouse gas emissions and cools the planet.

Twila Moon, deputy lead scientist at the National Snow and Ice Data Center in Colorado, said the findings are not surprising and reflect patterns seen by other researchers who modeled Greenland's ice sheet behavior.

Moon, who was not involved in the study, said it did a good job of showing "even if there's a temperature deviation, how quickly we can return" and that climate change actions would still matter even if global leaders do not reach their goals. "It's this transition that we as humanity need to make. And even if we don't get to our most ambitious goal, every tenth of a degree really matters," she said of reducing greenhouse gas emissions.

Greenland's ice sheet is already on a long-term path to disappearance. Moon said it has been losing mass every year since 1998, shedding an average of 3.4 Olympic-sized swimming pools' worth of freshwater every second over the past two decades.

The ice sheet loses mass as icebergs break off into the ocean and as surface melting occurs during the summer months in response to warming air temperatures.

According to the study in Nature, more than 20% of the global sea-level rise observed by scientists since 2002 has been caused by the melting of Greenland's ice sheet. Moon said Greenland's contribution to sea-level rise will only increase as average global temperatures rise further. Rising sea levels can cause coastal erosion, flooding, and the intrusion of salty water into freshwater drinking systems, among other problems.

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