Decrease in industrial pollution could spark droughts and floods
Global rainfall will increase significantly while arid regions will become drier if temperatures continue to rise and industrial pollution decreases, according to research from the Met Office.
The paper, published in Nature Climate Change, explains for the first time why there has been no increase in global average rainfall over land during the last century despite a 0.8 °C rise in global average temperatures.
According to the research, sulphate aerosol emissions from industrial pollutants have played a role in holding back increases in global rainfall, which were expected with a warming climate.
However, as this pollution decreases, as a result of more stringent regulations, and temperatures continue to rise due to global warming, scientists fear this will lead to more instances of extreme weather
Met Office's Improving Hydrological Predictions programme lead scientist and author of the paper Peili Wu said: "This research uses best available observations and the latest climate models to suggest something quite surprising; that instead of there being no change in global rainfall, we see a detectable slow-down between the 1950s and 80s followed by an increase in global rainfall.
"These changes are related to sulphate aerosols from industrial pollution which directly reflect sunlight, helping to initially slow the cycle of evaporation and rainfall. After the clean air acts of the 1980s, that cooling effect was partially removed and the cycle began to speed up again."
Greenhouse gases increase temperature at the earth's surface and higher up in the atmosphere, which should lead to an increase in rainfall overall due to the extra heat in the system.
However, industrial pollution blocks short wave solar radiation from reaching the surface of the earth reducing the heating there compared with higher elevations.
According to scientists, this will reduce convection and rainfall, but as aerosols are removed, convection will increase and the hydrological cycle will intensify.
Peter Stott, a co-author of the paper explained: "We could see the drier regions of the earth get even drier as they see faster evaporation, while the wet regions get wetter as additional moisture in the atmosphere falls as increased rainfall."