Vegetation forcing modulates global land monsoon and water resources in a CO2-enriched climate

Abstract

The global monsoon is characterised by transitions between pronounced dry and wet seasons, affecting food security for two-thirds of the world’s population. Rising atmospheric CO2 influences the terrestrial hydrological cycle through climate-radiative and vegetation-physiological forcings. How these two forcings affect the seasonal intensity and characteristics of monsoonal precipitation and runoff is poorly understood. Here we use four Earth System Models to show that in a CO2-enriched climate, radiative forcing changes drive annual precipitation increases for most monsoon regions. Further, vegetation feedbacks substantially affect annual precipitation in North and South America and Australia monsoon regions. In the dry season, runoff increases over most monsoon regions, due to stomatal closure-driven evapotranspiration reductions and associated atmospheric circulation change. Our results imply that flood risks may amplify in the wet season. However, the lengthening of the monsoon rainfall season and reduced evapotranspiration will shorten the water resources scarcity period for most monsoon regions.

Effects of Vegetation Changes and Multiple Environmental Factors on Evapotranspiration Across China Over the Past 34 Years

“…Furthermore, Cui et al. (2020) reported physiological effects of vegetation, like stomatal closure, may reduce E and raise flood risks in wet seasons. Therefore, under a changing climatic environment, the ways or areas of implementing ecological measures will greatly change the spatial distributions of Ea and Et and the runoff generation process.…”

“…Cui et al. (2020) claimed that stomata variation dominates the change in Et , not the effects of LAI . Ueyama et al.…”

“…On the one hand, increased vegetation in these areas would compete for the soil water; on the other hand, increased LAI would reduce radiation flux between the soil and atmosphere, which leads to a reduction in Ea and further increases in Et. Furthermore, Cui et al (2020) reported physiological effects of vegetation, like stomatal closure, may reduce E and raise flood risks in wet seasons. Therefore, under a changing climatic environment, the ways or areas of implementing ecological measures will greatly change the spatial distributions of Ea and Et and the runoff generation process.…”

“…To some extent, rising Et caused by increased LAI and decreased Et caused by the stomata closure exist at the same time. Cui et al (2020) claimed that stomata variation dominates the change in Et, not the effects of LAI. Ueyama et al (2020) calculated the Et reduction caused by CO 2 fertilization, with a value of −7.3% per 100 ppm.…”

Vegetation Response to Rising CO2 Amplifies Contrasts in Water Resources Between Global Wet and Dry Land Areas

“…A limited number of models contributed all of these three simulations to CMIP5 and we use four (CESM1‐BGC, IPSL‐CM5A‐LR, MPI‐ESM‐LR, and NorESM1‐ME; Table in the supporting information) in our analysis, which were selected as they are within ±1 standard deviation of estimated land transpiration to evapotranspiration (T/ET) ratios from isotope observations (Good et al., 2015). The ESMs with realistic values of T/ET may be expected to perform better at simulating future runoff changes (Lian et al., 2018) and biophysical feedbacks (Cui et al., 2020; Zeng et al., 2017). We use ESM diagnostics of monthly CMIP5 output.…”