Smog from Chinese industrial pollution could actually be reducing the country's contribution to climate change from methane, new research has indicated.
According to a report in New Scientist, the research, conducted by a British team, added sulphate to laboratory rice paddies in an effort to mimic the effect of acid rain on Asia's most important food crop.
"This equivalent of typical acid rain reduced methane emissions from flooded paddies by up to 25 per cent," said Vincent Gauci of the Open University in Milton Keynes in the UK.
Methane from agriculture is the second most important human-made greenhouse gas after carbon dioxide, and by some estimates up to a third of it comes from methane-generating bacteria lurking in rice paddies.
So, Asia's thickening smogs could be good news, in one respect, for the global climate.
That's as long as the acid rain does not simultaneously reduce the yield of rice fields, causing farmers to flood more and more fields to maintain production.
In fact, according to Gauci, "the acid rain seems to increase rice yields". That may be how the unexpected methane suppression operates.
By boosting grain production, the sulphur helps plants retain organic matter that once disappeared from their roots to trigger the manufacture of methane in the flooded fields.