Comment on esd-2022-47

Abstract

We compare apparent temperatures – that is a combination of 2 m air temperature, relative humidity and surface wind speed in four Earth System Models under the modest greenhouse emissions RCP4.5, the “business-as-usual" RCP8.5 and the stratospheric aerosol injection G4 geoengineering scenarios. Apparent temperatures come from both a 10 km resolution dynamically downscaled model (WRF), and a statistically bias corrected (ISIMIP) and downscaled simulation for the greater Beijing region. ISIMIP downscaling method tends to simulate apparent temperatures well at present in all seasons, and WRF produces warmer winters than does ISIMIP. WRF produces warmer winters and cooler summers than does ISIMIP in the future. These differences mean that estimates of numbers of days with extreme apparent temperatures vary systematically with downscaling method, as well as between climate models and scenarios. Air temperature changes dominate differences in apparent temperatures between future scenarios even more than they do at present because the reductions in humidity expected under solar geoengineering are overwhelmed by rising vapor pressure due to rising temperatures and the lower windspeeds expected in the region in all future scenarios. Urban centres see larger rises in extreme apparent temperatures than rural surroundings due to differences in land surface type, and since these are also the most densely populated, health impacts will be dominated by the larger rises in apparent temperatures in these urban areas.