Limiting warming to the target of “well below 2°C” may not be enough to prevent the disappearance of summer sea ice, scientists are warning.

As Reuters reports, a review of ice projections leads some scientists to believe that Arctic sea ice could vanish in summers even if governments meet the target set in the Paris Agreement on climate change. Under the agreement, governments agreed to limit average global temperatures to “well below 2°C,” with an aspirational target of 1.5°C.

“The 2C target may be insufficient to prevent an ice-free Arctic,” James Screen and Daniel Williamson of Exeter University wrote in the Nature Climate Change journal. Screen and Williamson project that a 2°C rise would mean a 39% risk of summer ice disappearance in the Arctic Ocean, but that ice was ‘virtually certain to survive’ under a 1.5°C scenario.