Parts of the Arctic are now predicted to be rain-dominated as early as 2060, two decades faster than previously expected
30 November 2021
Climate change could see the Arctic switch from being dominated by snow to rain up to two decades earlier than previously thought, with major consequences that risk accelerating global warming and devastating local wildlife.
Snow accounts for almost all current precipitation in the Arctic, but the region is warming faster than the rest of the world and is expected to become predominantly rainy this century. The transition has already begun: rain fell at Greenland’s highest summit this year, for the first time on record.
Now, an international team has found that the switch from snowy to rainy conditions across the Arctic could happen in 2060 rather than 2080. It will occur first in autumn, the season expected to see the biggest changes.
“It is all linked to the whole climate crisis, which is contributing to a much greater increase in rainfall. That has huge ramifications for all life in the Arctic and I’m not trying to be doomist,” says team member Michelle McCrystall at the University of Manitoba, Canada.
Reindeer and caribou herders in the Arctic face a huge impact as rain falling on snow can cover vegetation in ice, leading to the mass starvation of the herbivores, she says.
The switch to a mostly rainy Arctic would have global impacts too. It is expected to accelerate the thawing of frozen ground, releasing the greenhouse gases locked within, and speed up the already rapid loss of Arctic sea ice. Such positive feedbacks would fuel even faster climate change, the driver of the transition from snow to rain.
“Generally speaking, if the warming will cause earlier onset of Arctic rainfall that would obviously be bad for all kinds of reasons,” says Richard Bintanja at the University of Groningen in the Netherlands. A 2017 study he co-wrote warned of “widespread, long-lasting and possibly even irreversible consequences” from the transition.
The impact of a rainier Arctic on Greenland may be a mixed picture, say McCrystall and her colleagues. While rain will speed up melting at the edges of its ice sheet and drive sea level rise – a significant threat for coastal communities around the world – greater snowfall is expected in parts of Greenland that may offset some of the ice sheet’s loss of mass.
The earlier switch to a rain-dominated Arctic emerged after the team ran a new generation of more-sophisticated climate models, known as CMIP6, projecting the future based on historical observations of precipitation, surface air temperatures and other data.
Qinghua Ding at the University of California, Santa Barbara, who wasn’t involved in the research, says the shift to an earlier rain regime is to be expected, as the CMIP6 models treat the climate as more sensitive to the greenhouse gases we are pumping into the atmosphere.
One worrying finding of the new paper is that the switch to rain in many parts of the Arctic will now happen even if the world holds global warming to its goal of 1.5°C, rather than 2°C as previously thought. However, western European and Russian areas of the Arctic will still only transition to rain with 2°C of warming, showing that changes can be avoided if countries rein in their emissions.
Laura Landrum at the University Corporation for Atmospheric Research, US, who was not involved in the study, says it shows how limiting global warming to 1.5°C rather than as much as 3°C could have “profound” regional differences for the switch from snowy to rainy.
“We can make changes [to the outcomes],” says McCrystall. “It’s a call to action. Let’s do something about this, because it is going to affect everybody.”
Journal reference: Nature Communications, DOI: 10.1038/s41467-021-27031-y
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