Scientists Sound the Alarm over Widespread Drought in the 21st Century


 Drought is among the most damaging natural hazards in the world, often causing severe losses to agriculture, ecosystems and human societies. Scientists therefore have never stopped studying changes and variations in drought frequency and severity. 
"Historical records of precipitation, streamflow and observation-derived drought indices all show increased aridity since 1950s over several hotspot regions, including Africa, southern Europe, East Asia, eastern Australia, Northwest Canada, and southern Brazil." Said Prof. ZHAO Tianbao with the CAS Institute of Atmospheric Physics (IAP). "Climate model projections also suggest that drought may become more severe and widespread as the greenhouse gas-induced global warming continues in the 21st century." 
Recently, ZHAO and Prof. Aiguo DAI from University at Albany-State University of New York, further investigated hydroclimatic and drought changes in the latest projections from 25 models of the Phase Six of the Coupled Model Inetercomparison Project (CMIP6). 
Their results, published in Journal of Climate, suggest that the latest projections from CMIP6 models reaffirm the widespread drying and increases in agricultural drought by up to 200% over most of the Americas (including the Amazon), Europe and the Mediterranean region, southern Africa, Southeast Asia, and Australia under moderate-high emissions scenarios in the 21st century.
Frequency changes (%) of different drought metrics from 1970–99 to 2070–99 under the (left) SSP2-4.5 and (right) SSP5-8.5 scenarios projected by CMIP6 multimodel ensemble mean. (Plotted by IAP)
As if that wasn't bad enough, the drought is also expected to last longer and spread wider in the late twenty-first century (2070–99), ZHAO noted. The model results suggest a decrease in the mean and flattening of the probability distribution functions of drought metrics, despite large uncertainties in individual projections partly due to internal variability.
"With rising temperatures, everywhere there's increasing demand of moisture from atmosphere, and precipitation decreases over many subtropical regions. These are the main driver of the projected widespread and increasing drought." ZHAO explained.
Zhao, T., and A. Dai, 2022: CMIP6 model-projected hydroclimatic and drought changes and their causes in the 21st century. J. Climate, 35, 897–921,
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