During the mid-Piacenzian stage of late Pliocene, atmospheric CO₂ concentrations were similar to the modern value (410 ppmv), but the global mean temperature was 2–4°C higher than today. This discrepancy may be attributed to different intensity of internal climatic feedbacks, such as atmospheric water vapor content, and ice or cloud albedo distributions. In order to accurately predict future climate change trends, it is necessery to assess the relative contribution of these internal feedbacks. Here we developed a modified version of two-dimensional energy balance model (2D-EBM) of Zhuang and North (2017) with following new features. (1) Transient simulation is enabled with orbital parameters, CO2 and TSI (solar constant) forcings, which are updated at the beginning of each model year (or astronomical year, rather than calander year). (2) Temperature now can be outputted for each model year in the transient simulation or equilibrium simulation, rather than only the last model year (in the origin code). (3) By adding the subprogram, now the model can be restarted from the last time step. (4)Outputted timestep and monthly netcdf files are redefined and can be directly read by Grads software now.Then we conducted a series of equilibrium simulations to test the climate sensitivity under the standard boundary conditions of PlioMIP2 (CO₂ levels, land-sea distribution). Our results suggested that the global mean surface temperature has the largest sensitivity to changes of dynamic water vapor feedback, followed by dynamic ice albedo feedback, initial water vapor content and ice sheet area.

二维EBM模式,Pliocene,sensitivity analysis