Increasing contribution of evaporative demand to future intensified
drought across global drylands
Abstract
Drylands face more threat from droughts under global warming. It remains
insufficient in quantifying the roles of potential evapotranpiration
(PET) and precipitation (P) to drought changes in a warming climate.
Thus, we quantified the relative contributions of PET and P and
projected their future changes across global drylands under four
scenarios from Phase Six of the Coupled Model Intercomparison Project
(CMIP6) models. In the 21st century, the multimodel
medians of hydroclimatic fields indicate relatively consistent trend
patterns, showing a drying over most of global drylands except for East
Asia, Middle East, Sahel and South Asia drylands. The standardized
precipitation evapotranspiration index (SPEI) presents a robust and
ubiquitous drying with scenario-dependent magnitudes. The fractional
contributions of PET and P to the present-day drought changes are
estimated to be approximately equal (~50%). For the
near- and mid-term projections, PET (P) contributes
~58% (42%) and ~61%
(~39%), respectively. In the long-term, the fractional
contribution of PET (P) reaches ~65%
(~35%), ~72% (28%),
~80% (~20%), ~85%
(~15%) under four different scenarios, respectively.
Furthermore, PET contributes more significantly in the North Hemisphere
than in the South Hemisphere, particularly over the Mediterranean,
central and East Asian drylands. Drought conditions tend to be
relatively stable under low scenarios (SSP1-2.6 and SSP2-4.5), while
exacerbate continuously under high scenarios (SSP3-7.0 and SSP5-8.5). By
the end of 21st century, severe droughts like the
present-day 1-in-20-yr events are estimated to become fairly common
across global drylands. These results provide further understanding for
making policy and adaption strategies for drylands.