Exceeding 1.5C of global warming will have irreversible consequences for glaciers, sea ice and the Earth's frozen regions, two United Nations reports warned on Monday, calling for urgent action, AFP reported.
Source: AFP via Phys.org
One of the reports said overshooting the 1.5C target set under the landmark 2015 Paris Agreement "will bring large-scale and in many cases irreversible impacts" for the cryosphere — Earth's ice in all its forms. Melting glaciers and sea ice, thawing permafrost and accelerating sea-level rise will have widespread repercussions, from flooding to water shortages.
Even holding warming to 1.5C may not be enough. Current levels of warming are "already unsafe" for the Arctic, the Antarctic, mountain glaciers and polar oceans, the reports warned. "Although returning to 1.5C will slow ice loss, a truly 'safe' temperature for Earth's ice is now thought to be closer to 1C or even below over the coming centuries," one report said.
Global warming has already reached 1.37C above pre-industrial levels, and according to the European Copernicus network the 1.5C threshold could be exceeded around 2030, AFP said.
Source: AFP via Phys.org
"There are no good outcomes in exceeding 1.5C," said glaciologist James Kirkham, lead author of one of the reports, "Overshoot and the Cryosphere", which was written with 80 scientists. "To contain the global fallout and damage from ice loss in the world's polar and mountain regions, overshoot needs to be kept to the absolute minimum. Every extra fraction of a degree and every year spent in overshoot means more devastating impacts."
The second report, "State of the Cryosphere 2026: The Cost of Overshoot", released jointly by the UN Environment Programme and the International Cryosphere Climate Initiative, shows that exceeding 2.8C into the next century would have significant consequences: sea levels could rise by up to five centimetres (2 inches) a year by 2150, compared with the current 0.45 centimetres a year, while thawing permafrost could release as much carbon dioxide each year as the United States, the world's second-largest polluter.
Source: ICCI / UNEP via Zenodo
A worst-case but not-so-improbable scenario in the reports is that the world is heading toward warming of 2.6C by 2100 even if countries meet their current climate commitments. The scientists warned that crossing tipping points could make recovery very slow even if temperatures later fall: oceanographer Matthew England of the University of New South Wales said recovery could take "decades to centuries".
The damage is not theoretical. Switzerland has lost 20 percent of its glacier ice in the past five years, and Gunjan Silwal, a Nepali glacier researcher, said decisions made in the next few years "will lock in the scale of the damage", warning that August's mountain and glacier collapse in the Himalaya region, which killed more than 1,400 people and left over 5,000 missing, was "only a foretaste". For Punjab, whose rivers are fed by Himalayan snow and glaciers, the findings carry a direct warning about future water security.
Punjab's rivers and groundwater recharge depend on Himalayan snow and ice. The reports say mountain glaciers are already in the unsafe zone at today's warming — every extra fraction of a degree locks in more melt, more flood risk in the mountains and less reliable water downstream.
"Temporarily exceeding 1.5C does not mean that the goals of the Paris Agreement are irrelevant but instead makes them more urgent," Kirkham argued. "Returning to 1.5C or below by 2100 remains possible with sufficient political ambition and urgency, specifically by speeding the transition away from fossil fuel use to reach net zero by midcentury. Such urgent action can prevent and even reverse some cryosphere loss."