Global wet regions will not only receive more rainfall, but also experience temporally more varied rainfall events under global warming, according to researchers from the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences (CAS) and the UK Meteorological (Met) Office.
Their study was published in Science Advances on July 28.
From drinking water to hydroelectric energy, the amount of rainfall we receive, and when we receive it, has a significant impact on society and the environment. Rainfall variability is tightly associated with the occurrence of droughts and floods.
Using the Met Office's state-of-the-art climate model simulations and projections, scientists found that in a future warming world, climatologically wet regions will not only get wetter but also more variable, with greater differences between wet and dry conditions.
The increase in rainfall variability, on the whole, is projected to be larger than the increase in average rainfall, with the global mean increase in rainfall variability more than twice as large as the increase in mean rainfall (in a percentage sense).
"As climate warms, climatologically wet regions will generally get wetter and dry regions get drier. Such a global pattern of mean rainfall change is often described as 'wet-get-wetter'. By analogy, the global pattern of rainfall variability change features a 'wet-get-more variable' paradigm," said ZHOU Tianjun, corresponding author of the study.
ZHOU is a senior scientist at IAP and the CAS Center for Excellence in Tibetan Plateau Earth Sciences of CAS. He is also a professor at the University of Chinese Academy of Sciences.
Physically, while warming-induced atmospheric moistening acts to enhance rainfall variability worldwide, regional patterns of change in rainfall variability are dominated by change in circulation variability. "This highlights the importance of improving our understanding of future circulation changes, which is also an important source of uncertainty in climate change projections," said ZHANG Wenxia, lead author of the study.
"The amplified rainfall variability manifests the fact that global warming is making our climate more uneven--more extreme in both wet and dry conditions, with wider and probably more rapid transitions between them," added ZHANG. The resulting wider swings from one extreme to another will challenge the existing climate resilience of infrastructures, human society and ecosystems.
By simultaneously taking into account changes in the mean state and variability of precipitation, the research provides a new perspective for interpreting future precipitation change regimes. Around two-thirds of land will face a "wetter and more variable" hydroclimate, while the remaining land regions are projected to become "drier but more variable" or "drier and less variable."
"This classification of different precipitation change regimes is valuable for regional adaptation planning," said Kalli Furtado, Expert Scientist at the Met Office and second author of the study. "For most regions, the increasing rainfall variability, which could translate into impacts on crop yields and river flows, makes climate change adaptation more difficult."
The study was supported by the National Natural Science Foundation of China, the China Postdoctoral Science Foundation, the International Partnership Program of the Chinese Academy of Sciences, and the UK-China Research Innovation Partnership Fund.