Irreversible glacier change and trough water for centuries after overshooting 1.5°C
Abstract
Due to past climate inaction, exceeding a global mean temperature level of 1.5°C above pre-industrial levels has become a distinct possibility. Yet the consequences of such an overshoot are not well understood, including mountain glaciers' contribution to rising sea levels and regional water availability. Here we show that exceeding and then returning to the 1.5°C Paris Agreement limit has irreversible consequences for glacier mass and runoff over centuries. Novel global climate and glacier simulations project that a 3.0°C peak and decline scenario leads to 11% additional loss in global glacier mass by 2500 compared to limiting warming to 1.5°C without overshoot. In basins where glaciers regrow after peak temperature, glacier runoff reduces further than if the glaciers would stabilise, a newly documented phenomenon we call ″trough water″. Half of the studied glaciated basins show a lower glacier contribution to runoff with overshoot than without for decades to centuries post peak warming. These previously undocumented risks to glacier mass loss and runoff underscore the urgency of near-term emission reductions and limiting any potential climate overshoot.
Abstract
Section titled “Abstract”Abstract Due to past climate inaction, exceeding a global mean temperature level of 1.5°C above pre-industrial levels has become a distinct possibility. Yet the consequences of such an overshoot are not well understood, including mountain glaciers’ contribution to rising sea levels and regional water availability. Here we show that exceeding and then returning to the 1.5°C Paris Agreement limit has irreversible consequences for glacier mass and runoff over centuries. Novel global climate and glacier simulations project that a 3.0°C peak and decline scenario leads to 11% additional loss in global glacier mass by 2500 compared to limiting warming to 1.5°C without overshoot. In basins where glaciers regrow after peak temperature, glacier runoff reduces further than if the glaciers would stabilise, a newly documented phenomenon we call ″trough water″. Half of the studied glaciated basins show a lower glacier contribution to runoff with overshoot than without for decades to centuries post peak warming. These previously undocumented risks to glacier mass loss and runoff underscore the urgency of near-term emission reductions and limiting any potential climate overshoot.