The melting of the Greenland ice sheet could over time raise global sea levels by at least 25 centimeters, even if humans immediately stop burning the fossil fuels that are warming the planet to dangerous levels, according to a new study published in last Monday (29).
The study, published in Nature Climate Change, focuses on what the researchers call a “compromised” sea level rise, a measure that takes into account warming that has already occurred.
This approach differs from most previous research, which relied on computer modeling and generally predicted much smaller losses from the Greenland ice sheet. The latest assessment by the UN’s Intergovernmental Panel on Climate Change (IPCC), for example, projects something between 5 cm and 12 cm of sea level rise by 2100.
The new study’s forecast of 25 cm rise, which does not provide a timeline, could be much higher if temperatures continue to rise, as they almost certainly will, said Jason Box, a glaciologist at the Geological Survey of Denmark and Greenland, who was the main author of the work.
Box said the computer modeling typically used by glaciologists until now was “not up to the task” of representing how fast the ice sheets are melting. His team research studied satellite measurements taken between 2000 and 2019.
In the new study, the researchers examined what’s known as a weather snow line, or the boundary between a snow-covered and a snow-free surface, in the ice sheet.
The line varies annually in reaction to colder or warmer temperatures, and when one area grows larger than the other the ice sheet moves away from “equilibrium”. In a high-melt year, the snow line is pushed higher up on the ice sheet, which means that the area that accumulates snow is smaller, resulting in a smaller ice sheet.
The main problem with the new study is the lack of a time horizon associated with predictions, said Sophie Nowicki, an ice sheet expert in the geology department at the University at Buffalo, who was not involved in the research. Do you get to that number in 2100, she wrote in an email, “or in thousands of years?”
A good analogy for the study, she said, is the typical growth and weight charts you see when you take your kids to the doctor for an exam. Charts give an indication of how tall your child will be, but they are not good at predicting a growth spurt or the precise timing of growth.
The approach is “more grounded in what has already happened” than previous modeling of the ice sheet, and takes us beyond what has been done before, said John Walsh, chief scientist at the University of Alaska at Fairbanks, who was not involved in the study. study.
The findings indicate that even the most conservative estimate of ice melt can have dangerous effects for humans, Walsh said. While 25 cm may not seem like much on average, sea level does not rise equally everywhere. Some regions, especially lower coastal areas, can be hit by disproportionately devastating floods.
Translated by Luiz Roberto M. Gonçalves
