EDTW

To investigate the effect of EDTW on the Hadley expansion, we have conducted idealized warming experiments using the GFDL-AM2.1 atmosphere model. The Control simulation is forced with climatological SSTs and sea-ice cover averaged from 1980 to 2005. A global uniform CO2 concentration of 355 ppm is used and all other tracers for radiation computation are fixed at the values of the year 1990. The GW (global warming) simulation is forced with climatological SSTs plus the SST warming pattern (2080-2100 minus 1979-2005) derived from the RCP8.5 projections of CMIP5 models and with an increased CO2 concentration of 800 ppm. The enhanced SST warming in the tropical east Pacific (10oS to 10oN, 140oE to 80oW) is artificially removed in the GWnoEDTW (global warming without enhanced deep tropical warming) simulation by linear interpolation between -10oS to 10oN. The changes from GWnoEDTW to GW thus measure the effect of EDTW on future changes. All simulations are run for 55 years and the mean of the last 50 years are used for analysis.