Fig. 3: Underlying mechanisms.
From: Quasi-invariance of tropical meridional surface temperature gradient in a wide range of climates
a Incoming solar radiation at the top of the atmosphere (TOA). b The net shortwave radiation flux at the surface. c Air temperature at 500 hPa (other levels in the free troposphere have the same trend, shown in Fig. S4). d Changes in air temperature at 500 hPa, relatively to the pre-industrial (PI) experiment. e Changes in clear-sky greenhouse effect at TOA. f Changes in downward longwave radiation flux at the surface. In (a–c), the black line is for the ERA5 reanalysis data for the period of 2013–2022. All other data are from CESM1.2 simulations from 540 Ma to PI. All variables are for zonal and annual mean. The clear-sky greenhouse effect (\({G}_{c}\)) is defined as the difference between surface upwelling longwave flux and clear-sky outgoing longwave radiation at TOA (OLRc), \({G}_{c}\equiv \sigma {{T}_{s}}^{4}-{OLRc}\), where \({T}_{s}\) is surface temperature and \(\sigma\) is the Stefan-Boltzmann constant.
