Ecohydrological responses to solar radiation changes

Abstract. The potential implementation of future geoengineering projects alters solar radiation to counteract global warming trends. These changes could have effects on ecohydrological systems with impacts which are still poorly quantified. Here, we compute how changes in solar radiation affect global and local near surface meteorological variables by using CMIP6 scenario results and we compute climate sensitivities to solar radiation. These sensitivities are used to construct two sets of numerical experiments: the first focuses on solar radiation changes only, and the second systematically modifies precipitation, air temperature, specific humidity, and wind speed using the CMIP6 derived sensitivities to radiation changes, i.e., including its climate feedback. We use those scenarios as input to a mechanistic ecohydrological model to quantify the responses of the energy and water budget as well as vegetation productivity spanning different biomes and climates. In the absence of climate feedback, changes in solar radiation tend to reflect mostly in sensible heat changes, with minor effects on the hydrological cycle and vegetation productivity correlates linearly with changes in solar radiation. When climate feedback is included, changes in latent heat and hydrological variables are much more pronounced, mostly because of the temperature and vapor pressure deficit changes associated with solar radiation changes. Vegetation productivity tends to have an asymmetric response with a considerable decrease in gross primary production to a radiation reduction not accompanied by a similar increase with a radiation increase. These results provide important insights on how ecosystems could respond to potential future solar geoengineering programs.