Acid rain caused by industrial pollution could actually help reduce the greenhouse gas emissions of agriculture, say scientists.

Research led by the Open University's Dr Vincent Gauci suggests that sulphur-based acid rain from atmospheric pollution could cut the methane emissions associated with cultivating rice by almost a quarter.

Tonne for tonne, methane is more than 20 times more potent than carbon dioxide in terms of global warming.

Dr Gauci's findings suggest that, ironically, the high levels of pollution associated with China's rapid industrialisation may actually be going some small way towards mitigating its soaring CO2 output.

"Acid rain is one of several pollution problems in Asia that need solving in the coming decades but we need to appreciate the potential consequences of that clean up, one of which could be an increase in methane emissions as the effect of the acid rain wears off," said Dr Gauci.

"The reduction in pollution happens during a stage of the lifecycle when the rice plant is producing grain. This period is normally associated with around half of all methane emissions from rice and we found that simulated acid rain pollution reduced this emission by 24 per cent." said Dr Gauci.

The project , funded by the Natural Environment Research Council, used rice soils and grain from Portuguese paddies which have a similar chemical properties to Asian rice soils prior to their pollution.