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The warming of the global climate will cause aridification, complete with the expansion of deserts, especially in places like Australia and Africa.

But the degree to which the significant drying of selected regions will occur will be based on the extent of worldwide warming, reports a new study in the journal Nature Climate Change led by Chinese and British authors.

A crucial threshold will be 1.5 degrees Celsius – a key tipping point that has been pointed to by climate change experts – but which is more ambitious than the 2-degree limits codified in the international climate accord signed in Paris two years ago.

“Our research predicts that aridification would emerge over about 20-30 percent of the world’s land surface by the time the global mean temperature change reaches 2 degrees Celsius,” said Manoj Joshi, from the University of East Anglia, one of the authors. “But two-thirds of the affected regions could avoid significant ardification if warming is limited to 1.5 degrees Celsius.”

The meta-analysis incorporated projections from 27 separate global climate models. The threshold for aridification – a level based on the atmospheric water supply’s ratio to demand in key locations – was estimated based on global temperature increases.

“The areas of the world which would most benefit from keeping warming below 1.5 degrees Celsius are parts of Southeast Asia, Southern Europe, Southern Africa, Central America and Southern Australia,” said Tim Osborn, a professor from East Anglia who was also part of the work.

Droughts have already been made more severe by the beginning of the 21st century in places such as the Mediterranean basin and southern Africa, and deserts have spread in some areas of Mexico, Brazil and Australia, they write. 

Two of the forecasting models showed that 24 percent, or as much as 34 percent, of the total land mass reached the tipping point of drying out if 2 degrees of warming is reached.

But the “time of emergence for aridification,” or ToEA, is avoided in two-thirds of those additional regions if the warming is kept under 1.5 degrees Celsius, they found.

“Early action for accomplishing the 1.5 degrees Celsius temperature goal can therefor markedly reduce the likelihood that large regions will face substantial aridification and related impacts,” they conclude.

But the authors said even that level of warming could lead to impacts beyond just less water.

“Aridification is a serious threat because it can critical impact areas such as agriculture, water quality, and biodiversity,” said Chang-Eui Park of Southern University of Science and Technology in Shenzhen, China. “It can also lead to more droughts and wildfires – similar to those seen raging across California.

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