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Volcanoes are emitting up to three times more climate-cooling gases than previously thought, according to an analysis of tiny particles in a Greenland ice core.

Sulphate aerosols have a cooling聽effect on the climate by聽altering clouds and reflecting solar radiation. Gases released by volcanoes, marine phytoplankton and the burning of fossil fuels all contribute to the production of sulphate aerosols, but measuring the contribution from each source is聽very hard, so there is uncertainty about their climate impact.

To resolve this, at the University of Washington and her colleagues looked at sulphate particles trapped in Greenland ice. By gauging levels of various isotopes of sulphur, they could tell how much sulphate came from volcanoes and how much from marine sources between 1200 and 1850.

They found that volcanic sulphate emissions were much higher than expected. Even in the years without major eruptions, some two-thirds of the sulphate came from volcanoes . 鈥淭his suggests that degassing from non-erupting volcanoes is far more important than we thought,鈥� says Jongebloed.

Consequently, the team estimates that the cooling effect of human-made sulphate may only be half as potent as thought. 鈥淚t may explain why climate models are not quite able to replicate the high levels of warming we see in the Arctic,鈥� says Jongebloed. In other words, if you dial down the cooling effect of our sulphate pollution, the models might better replicate Arctic warming.

鈥淚t鈥檚 a really interesting study and it is certainly possible that we鈥檝e underestimated the impact of volcanic degassing globally, but aerosols don鈥檛 travel far from their source, so we can only draw conclusions about the Arctic region from this ice core,鈥� says at the University of Reading in the UK.