新的2100年冰川预测显示低排放和高排放政策之间存在严峻选择

Science, 6 January 2023

Improved glacier-specific projections that incorporate more detailed satellite measurements and ice dynamics forecast greater glacier loss already by 2100 with continued high emissions of today (resulting in 4°C by 2100), versus rapid emissions reduction this decade which keep global mean temperatures close to 1.5°C. The difference is especially stark for the mid-latitude glaciers of Western Canada and the US, Scandinavia, North Asia, Central Europe/Alps, New Zealand, the Caucasus, and low latitude glaciers (largely in Peru and Bolivia). For many glaciers in these regions, total or near-total loss would occur with continued high emissions already by 2100, sooner than previous less detailed model projections. Up to 40% of the total ice of glaciers in these regions would be preserved however with rapid emissions reductions consistent with the 1.5°C Paris Agreement limit. Several of these regions, including the Alps, Scandinavia, the Caucasus and New Zealand would pass a point of no return (total glacier loss) by 3°C, showing great sensitivity to temperatures above 1.5°C.

In High Mountain Asia, including glaciers of the Himalayas providing seasonal water resources to over 2 billion people, losses with low emissions would be slowed to maintain two-thirds of current ice, with risks of exceptional flooding moderated by mid-century. Glaciers in Central Asia and the southern Andes (Chile and Argentina) would preserve twice as much ice with rapid emissions reductions (about 50% globally by 2030) consistent with the 1.5°C limit. The study also examines the importance of the large marine-terminating glaciers in the Arctic and Antarctic, where (along with the highest altitudes of High Mountain Asia) the world’s remaining glaciers will be concentrated by 2100 should temperatures reach even 2°C.

Every increase in temperature “has significant consequences with respect to glacier contribution to sea level rise, the loss of glaciers around the world, and changes to hydrology, ecology, and natural hazards,” notes this comprehensive study, which includes several IPCC authors. They go on to caution, “Regardless of the temperature change scenario, all regions will experience considerable deglaciation…with roughly half of the world’s glaciers by number projected to be lost by 2100, even if temperature increase is limited to +1.5°C.” Noting that even fulfillment of Glasgow climate pledges would still result in 2.7°C, such a peak temperature would cause “the near-complete deglaciation of entire regions including Central Europe, Western Canada and US, and New Zealand compared with the Paris Agreement. The rapidly increasing glacier mass losses as global temperature increases beyond +1.5°C stresses the urgency of establishing more ambitious climate pledges,” the authors conclude, “to preserve the glaciers in these mountainous regions.”

https://www.science.org/doi/10.1126/science.abo1324