{"id":87803,"date":"2022-12-24T02:26:00","date_gmt":"2022-12-24T01:26:00","guid":{"rendered":"https:\/\/www.sonnenseite.com\/?p=87803"},"modified":"2022-12-22T18:27:01","modified_gmt":"2022-12-22T17:27:01","slug":"overshooting-climate-targets-could-significantly-increase-risk-for-tipping-cascades","status":"publish","type":"post","link":"https:\/\/www.sonnenseite.com\/en\/science\/overshooting-climate-targets-could-significantly-increase-risk-for-tipping-cascades\/","title":{"rendered":"Overshooting climate targets could significantly increase risk for tipping cascades"},"content":{"rendered":"\n

Temporarily overshooting the climate targets of 1.5-2 degrees Celsius could increase the tipping risk of several Earth system elements by more than 70 percent compared to keeping global warming in line with the United Nations Paris Agreement range, a new risk analysis study by an international team of researchers shows. This tipping risk increases even if in the longer term the global temperature would stabilize within the Paris range. Avoiding an overshoot would hence limit the risks, the researchers conclude.<\/p>\n\n\n

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\u00a9 Potsdam-Institut f\u00fcr Klimafolgenforschung 2022 | Map of the four interacting climate tipping elements. Each arrow represents a physical interaction mechanism between a pair of tipping elements, which can be destabilizing (denoted as +), stabilizing (denoted as \u2212) or unclear (denoted as \u00b1). AMAZ, Amazon rainforest; GIS, Greenland Ice Sheet; WAIS, West Antarctic Ice Sheet.<\/figcaption><\/figure>\n<\/div>\n\n\n

\u201cWe show that the risk for some tipping events could increase very substantially under certain global warming overshoot scenarios,\u201d explains Nico Wunderling, scientist at the Potsdam Institute for Climate Impact Research and lead-author of the study to be published in Nature Climate Change. \u201cEven if we would manage to limit global warming to 1.5 degrees after an overshoot of more than two degrees, this would not be enough as the risk of triggering one or more global tipping points would still be more than 50 percent. With more warming in the long-term, the risks increase dramatically.\u201d<\/p>\n\n\n\n

\u201cTo effectively prevent all tipping risks, the global mean temperature increase would need to be limited to no more than one degree \u2013 we are currently already at about 1.2 degrees,\u201c Jonathan Donges, Co-Lead of the FutureLab on Earth Resilience in the Anthropocene at PIK adds. \u201cThe latest IPCC report is showing that we\u2019re most likely on a path to temporarily overshoot the 1.5 degrees Celsius temperature threshold.\u201d<\/p>\n\n\n\n

Emergence of at least one tipping event increases with rising peak temperatures<\/h5>\n\n\n\n

To arrive at these results, the scientists, together with co-authors from the Earth Commission \u2013 a group of leading scientists convened by Future Earth \u2013 used different global warming overshoot scenarios with peak temperatures from two to four degrees and applied these to a set of four interacting tipping elements: the Greenland Ice Sheet, the West Antarctic Ice Sheet, the Atlantic Meridional Overturning Circulation AMOC, and the Amazon rainforest. The researchers applied a risk analysis approach based on millions of model simulations to reflect the uncertainties in relevant parameters such as the uncertainty in critical temperature thresholds as well as interaction strengths and interaction structure. Such an amount of simulations would be computationally too expensive to do based on fully coupled Earth System Model simulations. For the different overshoot scenarios, the research team then analyzed the risk of crossing critical thresholds and the potential for triggering cascading interactions between the four elements, depending on the magnitude and duration of the overshoot as well as the warming remaining on the long-term.

\u201cWe found that the risk for the emergence of at least one tipping event increases with rising peak temperatures \u2013 already at a peak temperature of three degrees Celsius, more than one third of all simulations showed a tipping event even when overshoot durations were limited strongly. At four degrees Celsius peak temperature, this risk extends to more than half of all simulations,\u201d explains Nico Wunderling.<\/p>\n\n\n\n

Tipping mechanisms under warming overshoots<\/h5>\n\n\n\n

\u201cEspecially the Greenland and the West Antarctic ice sheet are at risk of tipping even for small overshoots, underlining that they are among the most vulnerable tipping elements. While it would take a long time for the ice loss to fully unfold, the temperature levels at which such changes are triggered could already be reached soon,\u201d says Ricarda Winkelmann, Earth Commissioner and Co-Lead of the FutureLab on Earth Resilience in the Anthropocene. \u201cOur action in the coming years can thus decide the future trajectory of the ice sheets for centuries or even millennia to come.\u201d The other two tipping elements considered in the study, the AMOC and Amazon rainforest, have higher critical temperature thresholds. Yet, they would react much faster once the tipping process has started. Therefore, it is much more difficult to stop their tipping process once initiated by a temporary global warming overshoot.<\/p>\n\n\n\n

Current mitigation policies are expected to lead to 2-3.6 degrees Celsius of global warming by the end of this century. \u201cThis is not enough. Even though a temporary temperature overshoot would definitely be better than reaching a peak temperature and remaining there, some of the overshoot impacts may lead to irreversible damages in a high climate risk zone and this is why low-temperature overshoots are key here,\u201d explains Jonathan Donges. Ricarda Winkelmann adds: \u201cEvery tenth of a degree counts. We must do what we can to limit global warming as quickly as possible.\u201d<\/p>\n\n\n\n