The Early Eocene equable climate problem: can perturbations of climate model parameters identify possible solutions?
The Early Eocene equable climate problem: can perturbations of climate model parameters identify possible solutions?
复制标题
早始新世平等气候问题:气候模型参数的扰动能否找到可能的解决方案?
DOI:
10.1098/rsta.2013.0123
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发表时间:
2013
期刊:
影响因子:
--
通讯作者:
Sagoo N
中科院分区:
文献类型:
--
作者:
Sagoo N
Geological data for the Early Eocene (56–47.8 Ma) indicate extensive global warming, with very warm temperatures at both poles. However, despite numerous attempts to simulate this warmth, there are remarkable data–model differences in the prediction of these polar surface temperatures, resulting in the so-called ‘equable climate problem’. In this paper, for the first time an ensemble with a perturbed climate-sensitive model parameters approach has been applied to modelling the Early Eocene climate. We performed more than 100 simulations with perturbed physics parameters, and identified two simulations that have an optimal fit with the proxy data. We have simulated the warmth of the Early Eocene at 560 ppmv CO2, which is a much lower CO2level than many other models. We investigate the changes in atmospheric circulation, cloud properties and ocean circulation that are common to these simulations and how they differ from the remaining simulations in order to understand what mechanisms contribute to the polar warming. The parameter set from one of the optimal Early Eocene simulations also produces a favourable fit for the last glacial maximum boundary climate and outperforms the control parameter set for the present day. Although this does not ‘prove’ that this model is correct, it is very encouraging that there is a parameter set that creates a climate model able to simulate well very different palaeoclimates and the present-day climate. Interestingly, to achieve the great warmth of the Early Eocene this version of the model does not have a strong future climate change Charney climate sensitivity. It produces a Charney climate sensitivity of 2.7°C, whereas the mean value of the 18 models in the IPCC Fourth Assessment Report (AR4) is 3.26°C±0.69°C. Thus, this value is within the range and below the mean of the models included in the AR4.
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