World to become drier with global warming of 20 C

London: Over a quarter of the world's land could become significantly drier even if global warming is limited to the target of two degree Celsius, according to scientists including one of Indian origin. 

The change would cause an increased threat of drought and wildfires. However, limiting global warming to under 1.5 degree Celsius would dramatically reduce the fraction of the Earth's surface that undergoes such changes. 

Researchers from University of East Anglia (UEA) in the UK and Southern University of Science and Technology (SUSTech) in China studied projections from 27 global climate models.

 They identified the areas of the world where aridity will substantially change when compared to the year-to-year variations they experience now, as global warming  reaches 1.5 or two degree Celsius above pre-industrial levels.

 Aridity is a measure of the dryness of the land surface, obtained from combining precipitation and evaporation. "Our research predicts that aridification would emerge over about 20-30 per cent of the world's land surface by the time the global mean temperature change reaches two degrees Celsius," said Manoj Joshi from UEA.

 "But two thirds of the affected regions could avoid significant aridification if warming is limited to 1.5 degrees Celsius," said Joshi, one of the authors of the study published in the journal Nature Climate Change.  Drought severity has been increasing across the Mediterranean, southern Africa, and the eastern coast of Australia over the course of the 20th Century, while semi-arid areas of Mexico, Brazil, southern Africa and Australia have encountered desertification for some time as the world has warmed.  "Aridification is a serious threat because it can critically impact areas such as agriculture, water quality, and biodiversity. It can also lead to more droughts and wildfires - similar to those seen raging across California," said Chang-Eui Park from SusTech.

 "Another way of thinking of the emergence of aridification is a shift to continuous moderate drought conditions, on top of which future year-to-year variability can cause more severe drought," said Park.

 "For instance, in such a scenario 15 per cent of semi- arid regions would actually experience conditions similar to 'arid' climates today," he said. "The world has already warmed by one degree Celsius. But by reducing greenhouse gas emissions into the atmosphere in order to keep global warming under 1.5 degrees Celsius or two degrees Celsius could reduce the likelihood of significant aridification emerging in many parts of the world," Joshi said.

 "The areas of the world which would most benefit from keeping warming below 1.5 degree Celsius are parts of South East Asia, Southern Europe, Southern Africa, Central America and Southern Australia - where more than 20 per cent of the world's population live today," said Tim Osborn from UEA.