A recent study conducted in Sweden, the United States and China showed that the number of days with light rainfall (less than 0.1 millimetre per day) dropped by 23 percent in China from 1956 to 2005.

That was because of air pollution particles that reduced the formation of rain clouds, researcher Deliang Chen of Gothenburg University said.

"The particles of air pollution, named aerosols, make the drops of water considerably smaller and that makes them more difficult to aggregate into rain clouds that can release rain," he said.

While the amount of rain has remained stable over the years, the reduction of light rainfalls, or "good rainfalls", poses a threat to China as the country drags its feets on reducing greenhouse gas emissions, he said.

"Light rains in a country like China are counted upon because they're easy for the soil to absorb. But heavy rains make the soil run off and the water is not absorbed and can cause problems such as erosion or floodings," he said.

"Now we have evidence that air pollution is not only bad for the climate but also for the agriculture and the economy," he added.

The study, entitled "Heavy pollution suppresses light rain in China," was published recently in the US Journal of Geophysical Research.

Northern China is the region most exposed to drought.

It is currently experiencing its worst drought in 60 years, leaving nearly five million people short of water, state media have reported.