At least a quarter of the land surface of the Earth will become "considerably" drier even if global warming is kept below the upper international target of two degrees Celsius, according to new research published Monday.

But if the global temperature increase is held to the more ambitious target of 1.5 degrees above pre-industrial levels, a much smaller fraction of the planet's surface — one-12th — would suffer that fate, researchers say.

The dryness of the Earth's surface, known as aridity, is a major factor in determining the incidence of natural disasters like drought and wildfires. Increases in aridity, or aridification, in a region tend to lead to the degradation of land and, eventually, desertification.

"Aridification is a serious threat because it can critically impact areas such as agriculture, water quality, and biodiversity," study lead author Chang-Eui Park of China's Southern University of Science and Technology said in a statement.

Park and colleagues used 27 different global climate models to project how much aridification the Earth would undergo as average temperatures rise.

According to their calculations, if planetary warming reaches two degrees Celsius — which would happen sometime between 2052 and 2070 — then 24 to 32 per cent of the Earth's surface would become drier. Those areas would not turn into arid regions per se, but would just be drier than they are today.

With warming of 1.5 degrees C, fewer regions would suffer aridification. Areas that would be spared major effects include parts of of Central America, the Australian coast, southern Africa, Southern Europe and Southeast Asia, the researchers concluded.

Desertification already underway

The planet has already warmed one degree since pre-industrial times, and most climate scientists agree that temperature change is significantly responsible for increasing drought or desertification from Brazil to the Mediterranean and Australia.

The Paris climate accord aims to limit the global average temperature rise to well below two degrees Celsius above pre-industrial levels, with a preferred target of 1.5 degrees.

"Early action for accomplishing the 1.5 degree Celsius temperature goal can… markedly reduce the likelihood that large regions will face substantial aridification and related impacts," the new study concludes.

The research was published online in the journal Nature Climate Change.