The Early Eocene equable climate problem: can perturbations of climate model parameters identify possible solutions?

摘要: 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 prediction of these polar surface temperatures, resulting so-called ‘equable climate problem’. In paper, first time an ensemble a perturbed climate-sensitive model parameters approach has been applied modelling climate. We performed more than 100 simulations physics parameters, and identified two that have optimal fit proxy data. simulated warmth 560 ppmv CO 2 , which is much lower level many other models. investigate changes atmospheric circulation, cloud properties ocean circulation common how they differ from remaining order understand what mechanisms contribute warming. The parameter set one also produces favourable last glacial maximum boundary outperforms control present day. Although does not ‘prove’ correct, it encouraging creates able well different palaeoclimates present-day Interestingly, achieve great version strong future change Charney sensitivity. It sensitivity 2.7 ° C, whereas mean value 18 models IPCC Fourth Assessment Report (AR4) 3.26 C±0.69 C. Thus, within range below included AR4.