Acid rain stops global warming

In a case of the bugbear of the 1980s meeting the hobgoblin of the 1990s, scientists have found that acid rain can slow global warming by reducing methane emissions from natural wetland areas.

The new study, led by Vincent Gauci of Britains Open University together with colleagues at NASA and published in Proceedings of the National Academy of Sciences, finds that acid rain counteracts the natural production of methane gases by microbes in wetland areas.

As New Scientist says (Aug. 3), “Methane is thought to account for 22 percent of the human-enhanced greenhouse effect. And microbes in wetland areas are its biggest producers. They feed off substrates such as hydrogen and acetate in peat and emit methane into the atmosphere.”

The theory is that global warming itself will speed up the production of methane, “as heating up the microbes causes them to produce even more methane. But the new model suggests that sulphur [sic] pollution from industry cancels this out. This is because sulphur-eating bacteria also found in wetland regions outcompete the methane-emitting microbes for substrates. Experiments have shown that sulphur deposits can reduce methane production in small regions by up to 30 per cent by activating sulphur-eating bacteria.”

Atmospheric concentrations of methane have leveled off in the past few years.