ACINN Graduate Seminar - WS 2023/24

2024-01-17 at 12:00 (on-line and on-site)

Consequences of overshooting the Paris temperature targets for global glacier volume and runoff projections

Lilian Schuster

ACINN, University of Innsbruck, Austria

 

Mountain glaciers contribute significantly to sea level rise and to water availability during droughts. Due to past and future rising temperatures, continued glacier mass loss is projected for the 21st century and beyond. We will start the seminar by discussing the latest multi-model glacier model projection estimates until 2300 that appeared in the recent International Cryosphere Climate Initiative - State of the Cryosphere Report published for the COP28 in Dubai. We then delve into the impacts of overshooting the 1.5°C Paris Agreement target and returning to it afterwards, because, with every day, overshooting the 1.5°C target gets more likely. We will explore the effects of these peak-and-decline overshoot scenarios on glacier volume and runoff using the Open Global Glacier Model (OGGM) framework. We use novel climate simulations of an Earth System Model from 2000 to 2500 that either stabilise at global warming levels of 1.2°C (current warming), 1.5°C and 3°C, or temporally overshoot 1.5°C peaking at 3°C before declining and stabilising at 1.5°C after 2300. The time-delayed global glacier response results in irreversible ice loss over centuries although for some glacier regions the model projects regrowth within a century after the overshoot. In glacier regions that regrow within the simulation period after a temporal temperature overshoot, glacier runoff contribution reduces temporally further than if temperature stabilises (“trough water”). We find that the importance of this newly documented “trough water” depends on local conditions such as the volume response time, local temperature overshoot magnitude, melt versus precipitation seasonality and future precipitation shifts.

 

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