Are there pre-Quaternary geological analogues for a future greenhouse warming?
Are there pre-Quaternary geological analogues for a future greenhouse warming?
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DOI：
10.1098/rsta.2010.0317
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发表时间：
2011-03-13
期刊：
影响因子：
5
通讯作者：
Williams, Mark
中科院分区：
文献类型：
--
作者：
Haywood, Alan M.;Ridgwell, Andy;Williams, Mark
考虑到预测气候和环境对人为温室气体排放的反应存在固有的不确定性，如果科学能够识别出与人类当前大规模气候实验类似的地质现象，将对社会有益。在过去的30年里，这一直是地质和古气候学界关注的焦点，许多科学论文声称，地球历史的间隔可以用作未来气候变化的类比。使用耦合的海洋-大气模拟方法，我们对过去1亿年最可能的前第四纪候选者进行了验证：中白垩纪和晚白垩纪，古新世-始新世热最大值（PETM），早始新世，以及中新世和上新世的温暖间隔。这些时间间隔不能作为真正的直接类比，因为它们要么代表了长期二氧化碳强迫的平衡气候状态——而温室气体的人为排放对气候提供了一个渐进的（短暂的）强迫——要么气候系统本身对二氧化碳的敏感性是不同的。虽然没有相似的地质模拟存在，但地球历史上过去的温暖间隔为研究在温暖（高二氧化碳）气候状态下运行的过程提供了独特的机会。古气候和环境重建/模拟正在促进全球温度对较长期（多个世纪）二氧化碳浓度增加的响应的评估和计算；这现在被称为地球系统敏感性，它对于确定大气中二氧化碳的阈值至关重要，这些阈值必须不被越过，以避免长期气候变化的危险水平。古气候学还提供了一种独特而独立的方法来评估用于预测未来气候的气候和地球系统模式的质量。
Given the inherent uncertainties in predicting how climate and environments will respond to anthropogenic emissions of greenhouse gases, it would be beneficial to society if science could identify geological analogues to the human race's current grand climate experiment. This has been a focus of the geological and palaeoclimate communities over the last 30 years, with many scientific papers claiming that intervals in Earth history can be used as an analogue for future climate change. Using a coupled ocean-atmosphere modelling approach, we test this assertion for the most probable pre-Quaternary candidates of the last 100 million years: the Mid-and Late Cretaceous, the Palaeocene-Eocene Thermal Maximum (PETM), the Early Eocene, as well as warm intervals within the Miocene and Pliocene epochs. These intervals fail as true direct analogues since they either represent equilibrium climate states to a long-term CO2 forcing-whereas anthropogenic emissions of greenhouse gases provide a progressive (transient) forcing on climate-or the sensitivity of the climate system itself to CO2 was different. While no close geological analogue exists, past warm intervals in Earth history provide a unique opportunity to investigate processes that operated during warm (high CO2) climate states. Palaeoclimate and environmental reconstruction/modelling are facilitating the assessment and calculation of the response of global temperatures to increasing CO2 concentrations in the longer term (multiple centuries); this is now referred to as the Earth System Sensitivity, which is critical in identifying CO2 thresholds in the atmosphere that must not be crossed to avoid dangerous levels of climate change in the long term. Palaeoclimatology also provides a unique and independent way to evaluate the qualities of climate and Earth system models used to predict future climate.