More than a quarter of Earth's land surface will become "significantly" drier even if humanity manages to limit global warming to two degrees Celsius, the goal espoused in the Paris Agreement, scientists said on Monday.
But if we contain average warming to 1.5 C (2.7 degrees Fahrenheit), this will be limited to about a tenth -- sparing two-thirds of the land projected to parch under 2 C, they concluded in a study published in Nature Climate Change.
At 1.5 C, parts of southern Europe, southern Africa, central America, coastal Australia and Southeast Asia -- areas home to more than a fifth of humanity -- "would avoid significant aridification" predicted under 2 C, said study co-author Su-Jong Jeong of the Southern University of Science and Technology in Shenzhen, China.
"Accomplishing 1.5 C would be a meaningful action for reducing the likelihood of aridification and related impacts," he told AFP.
Jeong and a team used projections from several climate models, under different warming scenarios, to predict land drying patterns.
Aridification is a major threat, hastening land degradation and desertification, and the loss of plants and trees crucial for absorbing Earth-warming carbon dioxide.
It also boosts droughts and wildfires, and affects water quality for farming and drinking.
The team found that at 2 C, which could arrive any time between 2052 and 2070, between 24 percent and 32 percent of the total land surface will become drier.
This includes land in all five climate categories today -- hyper-arid, arid, semi-arid, dry sub-humid, and humid.
But at 1.5 C -- the lower, aspirational limit also written into the climate-rescue Paris Agreement -- this is reduced to between eight and 10 percent, said Jeong.
Under the pact, signed in the French capital in 2015, countries have filed pledges for reducing climate-altering greenhouse gas emissions from burning coal, oil and natural gas.
But these goals place the planet on track for warming of more than 3 C, which scientists warn will lead to life- and asset-threatening superstorms, sea-level rise, floods and drought.
"Because present mitigation policies do not appear to be sufficient to achieve the 1.5 C temperature goal, more efforts to mitigate global warming are therefore urgently needed to reduce the spread of aridification," the study authors said.