Climate bifurcations in a Schwarzschild equation model of the Arctic atmosphere

[摘要] A column model of the Arctic atmosphere is developed including the nonlinear positive feedback responses of surface albedo and water vapour to temperature. The atmosphere is treated as a grey gas and the flux of longwave radiation is governed by thetwo-stream Schwarzschild equations.Water vapour concentration is determined by the Clausius–Clapeyron equation. Representative concentration pathways (RCPs) are used to model carbon dioxide concentrations into the future.The resulting 9D two-point boundary value problem is solved under various RCPs and the solutions analysed. The model predicts that under the highest carbon pathway, the Arctic climate will undergo anirreversible bifurcation to a warm steady state, which would correspond to annually ice-freeconditions.Under the lowest carbon pathway, corresponding to very aggressive carbon emission reductions,the model exhibits only a mild increase in Arctic temperatures.Under the two intermediate carbon pathways, temperatures increase more substantially, andthe system enters a region of bistability where external perturbations could possiblycause an irreversible switch to a warm, ice-free state.

[学科分类] 自动化工程