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Overshooting tipping point thresholds in a changing climate
Nature ( IF 50.5 ) Pub Date : 2021-04-21 , DOI: 10.1038/s41586-021-03263-2
Paul D. L. Ritchie , Joseph J. Clarke , Peter M. Cox , Chris Huntingford

Palaeorecords suggest that the climate system has tipping points, where small changes in forcing cause substantial and irreversible alteration to Earth system components called tipping elements. As atmospheric greenhouse gas concentrations continue to rise as a result of fossil fuel burning, human activity could also trigger tipping, and the impacts would be difficult to adapt to. Previous studies report low global warming thresholds above pre-industrial conditions for key tipping elements such as ice-sheet melt. If so, high contemporary rates of warming imply that exceeding these thresholds is almost inevitable, which is widely assumed to mean that we are now committed to suffering these tipping events. Here we show that this assumption may be flawed, especially for slow-onset tipping elements (such as the collapse of the Atlantic Meridional Overturning Circulation) in our rapidly changing climate. Recently developed theory indicates that a threshold may be temporarily exceeded without prompting a change of system state, if the overshoot time is short compared to the effective timescale of the tipping element. To demonstrate this, we consider transparently simple models of tipping elements with prescribed thresholds, driven by global warming trajectories that peak before returning to stabilize at a global warming level of 1.5 degrees Celsius above the pre-industrial level. These results highlight the importance of accounting for timescales when assessing risks associated with overshooting tipping point thresholds.



中文翻译:

在不断变化的气候中超过临界点阈值

古记录表明,气候系统具有引爆点,在这些引爆点上,微小的强迫变化会导致被称为引爆元素的地球系统组件发生实质性且不可逆的变化。由于化石燃料燃烧导致大气温室气体浓度持续上升,人类活动也可能引发倾翻,其影响将难以适应。先前的研究报告指出,在关键冰雪融化等关键倾覆元素中,全球变暖阈值高于工业化之前的水平。如果是这样,那么当代的高升温速度就意味着超过这些阈值几乎是不可避免的,这被广泛认为意味着我们现在正致力于遭受这些倾覆事件。在这里,我们证明了这种假设可能是有缺陷的,特别是对于在我们快速变化的气候中慢速倾翻的要素(例如大西洋经络翻转环流的崩溃)。最近发展的理论表明,如果超调时间比倾翻元件的有效时标短,则可以在不提示改变系统状态的情况下暂时超过阈值。为了证明这一点,我们考虑了具有规定阈值的倾斜元素的透明简单模型,这些模型由全球变暖轨迹驱动,这些轨迹在恢复稳定至高于工业化前水平1.5摄氏度的全球变暖水平之前达到峰值。这些结果突显了在评估与超临界点阈值相关的风险时考虑时间表的重要性。最近发展的理论表明,如果超调时间比倾翻元件的有效时标短,则可以在不提示改变系统状态的情况下暂时超过阈值。为了证明这一点,我们考虑了具有规定阈值的倾斜元素的透明简单模型,这些模型由全球变暖轨迹驱动,这些轨迹在恢复稳定至高于工业化前水平1.5摄氏度的全球变暖水平之前达到峰值。这些结果突显了在评估与超临界点阈值相关的风险时考虑时间表的重要性。最近发展的理论表明,如果超调时间比倾翻元件的有效时标短,则可以在不提示改变系统状态的情况下暂时超过阈值。为了证明这一点,我们考虑了具有规定阈值的倾斜元素的透明简单模型,这些模型由全球变暖轨迹驱动,这些轨迹在恢复稳定至高于工业化前水平1.5摄氏度的全球变暖水平之前达到峰值。这些结果突显了在评估与超临界点阈值相关的风险时考虑时间表的重要性。我们考虑了具有规定阈值的引爆元素的简单透明模型,这些模型由全球变暖轨迹驱动,这些轨迹在恢复稳定至高于工业化前水平1.5摄氏度的全球变暖水平之前达到峰值。这些结果突显了在评估与超临界点阈值相关的风险时考虑时间表的重要性。我们考虑了具有规定阈值的引爆元素的简单透明模型,这些模型由全球变暖轨迹驱动,这些轨迹在恢复稳定至高于工业化前水平1.5摄氏度的全球变暖水平之前达到峰值。这些结果突显了在评估与超临界点阈值相关的风险时考虑时间表的重要性。

更新日期:2021-04-21
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