UN reports warn glacier and sea-ice losses may be irreversible above 1.5C warming

What the UN reports say

Two United Nations reports published on Monday, 2 November 2026, warn that global warming above 1.5C over pre-industrial levels would bring significant and often irreversible consequences for the cryosphere, the frozen parts of the planet made up of snow, ice and frozen ground. The threshold is the most ambitious goal of the Paris Agreement. One report, drawn up by 80 scientists working with the International Cryosphere Climate Initiative (ICCI) and the UN Environment Programme (UNEP), argues that a temporary overshoot would still cause lasting losses of ice. The authors call for action "as quickly as possible" ahead of COP31, where countries are due to discuss measures against global warming.

Warming already near the threshold

Estimates of current warming differ between accounts of the reports. AFP puts the rise at 1.37C above pre-industrial levels, while the Guardian gives 1.3C. The European Copernicus network estimates the 1.5C threshold could be exceeded around 2030. Scientists say failures to curb greenhouse gas emissions have made some overshoot of the target effectively unavoidable. The reports describe 1.5C as already too high for the cryosphere, whose safe temperature sits closer to 1C or even lower.

The overshoot scenario

According to the Guardian's account, the high overshoot expected under current policies, with peak temperatures of about 3C, would thaw nearly all near-surface permafrost. The same path would make severe and possibly abrupt disruption to ocean circulation likely, and lead to widespread acidification. The report also finds that the latest research suggests sea ice recovers more slowly than previously thought. The authors want time above 1.5C kept as short as possible, and enough carbon removed from the atmosphere to bring long-term warming below 1C by 2150. Scientists also flag the risk of crossing critical tipping points, which would make certain changes effectively irreversible.

Glacier losses and the second report

James Kirkham, a glaciologist at ICCI and lead author of one of the reports, described the cryosphere as one of the most sensitive parts of the climate system, with losses affecting the whole planet. He pointed to glacier losses already visible in Switzerland.

“Switzerland has lost 20% of its glacier ice in the last five years”

The second report models a 2.8C overshoot that would continue into the next century. In that scenario sea levels could rise by as much as 5 cm a year by 2150, compared with 0.45 cm a year at present, according to La Libre's account. Thawing permafrost could also release each year as much CO2 as the United States, the world's second-largest polluter, currently emits.

What happens next

Some glaciers could partly regrow if warming returned quickly below 1.5C on average, or even 1C, and Arctic sea ice could benefit as well. Chen Zhao, a glaciologist specialising in Antarctica and a contributor to the reports, warned that bringing warming back below the threshold would not undo the consequences of the period when it was exceeded. Kirkham stressed that each extra fraction of a degree and each year spent above the threshold would bring more devastating consequences. The reports were published roughly a week before COP31.