Dec. 22 () –
Temporarily exceeding climate targets of 1.5 to 2 degrees Celsius could increase the risk of tipping over several elements of the Earth system by more than 70 percent.
According to a new risk analysis study by an international team, this risk of tipping points increases even if, over the long term, the global temperature were to stabilize within the Paris range. Therefore, avoiding an excess would limit the risks, the researchers conclude in their work, published in the journal ‘Nature Climate Change’.
“We show that the risk of some tipping events occurring could increase very substantially in certain scenarios of exceeding global warming,” he explains. it’s a statement Nico Wunderling, a scientist at the Potsdam Institute for Climate Impact Research in Germany and lead author of the study.
“Even if we managed to limit global warming to 1.5 degrees after an exceedance of more than two degrees, it would not be enough, since the risk of triggering one or more global inflection points would still be greater than 50% –alert– . With more long-term warming, risks rise dramatically“.
Therefore, “to effectively prevent all tipping risks, the increase in global average temperature would have to be limited to no more than one degree and we are currently already at around 1.2 degrees,” adds Jonathan Donges, Co-Leader of the FutureLab on Earth Resilience in the Anthropocene at PIK–. The latest IPCC report shows that we will most likely temporarily exceed the temperature threshold of 1.5 degrees Celsius.”
To arrive at these results, the scientists, along with co-authors from the Earth Commission — a group of leading scientists convened by Future Earth — used different global warming-exceed scenarios with maximum temperatures of 2 to 4 degrees Celsius and applied them to to a set of four interacting tipping elements: the Greenland Ice Sheet, the West Antarctic Ice Sheet, the southern overturning circulation of the Atlantic AMOC and the Amazon rainforest.
The researchers applied a risk analysis approach based on millions of model simulations to account for uncertainties in relevant parameters such as uncertainty in critical temperature thresholds, as well as the intensities of interaction and the structure of interaction.
Such a number of simulations would be too computationally expensive to rely on fully coupled Earth system model simulations.
For the different exceedance scenarios, the research team then analyzed the risk of crossing critical thresholds and the potential to trigger cascading interactions between the four elements, depending on the magnitude and duration of the overshoot, as well as the long-term remnant warming.
“We found that the risk of occurrence of at least one tipping event increases with increasing maximum temperatures: already at a maximum temperature of three degrees Celsius, more than a third of all simulations showed a tipping event even when durations of the overshoot were strongly limited.At a maximum temperature of four degrees Celsius, this risk extends to more than half of all simulations“, explains Nico Wunderling.
“The Greenland ice sheet and the West Antarctic ice sheet are at risk of capsizing with even small excesses, which reveals that they are among the most vulnerable dump elements“, says Ricarda Winkelmann, Earth Commissioner and co-director of the FutureLab on Earth’s resilience in the Anthropocene.
“Although ice loss would take a long time to fully unfold, the temperature levels at which such changes are triggered could be reached already soon,” he continued. Our performance in the coming years may thus decide the future trajectory of the ice sheets for centuries or even millennia.“.
The other two tipping elements considered in the study, the AMOC and the Amazon rainforest, have higher critical temperature thresholds. However, they would react much faster once the tipping process started. It is therefore much more difficult to stop its tipping process. once initiated by a temporary overshoot of global warming.
Current mitigation policies are projected to lead to global warming of between 2 and 3.6 degrees Celsius by the end of this century. “This is not enough. Although a temporary temperature exceedance would certainly be better than reaching a maximum temperature and staying there, some of the impacts of the exceedance can cause irreversible damage in an area of high climate risk, and therefore temperature exceedances low temperatures are key in this case –Jonathan Donges warns.
“Every tenth of a degree counts,” Ricarda Winkelmann insists. We must do what we can to limit global warming as soon as possible.”
