Air pollution from Europe contributed to one of the worst ever droughts in India, which affected over 130 million people in the country in 2000, a new study has found.

Researchers at Imperial College London in the UK calculated the effect of sulphur dioxide emissions on rainfall in India in the year 2000.

They found that India's north-western regions experienced a staggering drop of about 40 per cent in rainfall because of emissions from the northern hemisphere's main industrial areas, 'The Independent' reported.

Europe's emissions alone caused reductions of up to 10 per cent in the north-west and south-west regions, researchers said.

Sulphur dioxide – produced mainly by coal-fired power plants - causes a number of harmful effects, such as acid rain, heart and lung diseases, and damage to plant growth.

Sulphate aerosols also have a cooling effect on the atmosphere because it reflects sunlight back into space. Emissions from the northern hemisphere can change the relative rate of warming with the south, causing the tropical rain-band to shift - with potentially devastating results.

The study shows how emissions in one part of the world could have a significant effect on another - even if the pollution itself did not actually get there, said Apostolos Voulgarakis, of ICL's Grantham Institute.

"East Asia is contributing more because (of an effect) because it is closer, but there is an effect from Europe and also the US," Voulgarakis said.