The team gave 650 people 10 euros to donate to climate-change mitigation projects if they wished; those who had been told that aerosol injection could partly address the climate-change problem donated more. This suggests, contrary to predictions, that giving people information about aerosol injection – a controversial method of geoengineering the climate – does not necessarily affect their commitment to mitigation.

"This is the first indication that people will not easily accept aerosol injection as a quick fix, be drawn into conclusions and reduce their mitigation efforts, which is often suggested," said Christine Merk of the Kiel Institute for the World Economy. "People still prefer mitigation, especially when they are presented with aerosol injection as an alternative way of addressing climate change."

Aerosol injection involves releasing large quantities of sulphate or other particles into the stratosphere to reflect some of the sun’s radiation, and hence cool temperatures. The process, which would be similar to the eruption of several large volcanoes over many decades, is controversial, not least because it would not solve all of the problems associated with the continued emission of greenhouse gases, such as ocean acidification.

Researchers have often predicted that simply giving people information about the possibility of geoengineering with aerosols would reduce the amount they are willing to commit to climate-change mitigation. One hypothesis is that people readily accept arguments exonerating them from difficult responsibilities. Merk and colleagues wanted to put this belief to the test. "Our study is the first to look at actual changes in behaviour," said Merk.

The researchers gave a cross-section of 650 German citizens basic information about climate change that was in line with conclusions from the latest report of the Intergovernmental Panel on Climate Change. A portion of the group also received basic details about aerosol injection as a potential way to address climate change, including information about the method’s uncertainty and risks. Finally, all people in the group were asked a few questions to check their understanding before being given 10 euros, which they could either take away or spend on carbon offsets.

Merk and colleagues found that those who had received information on aerosol injection donated, on average, €0.77 more to carbon offsets. "Our suspicion is that people who actually think it is a realistic idea are afraid of it, and are thus spurred to mitigate more," said Merk. "Theories had suggested it would be the other way round."

Merk and colleagues are now preparing a project that will investigate the effect of different ways of presenting information, and try to uncover exactly why people spend more on mitigation if they know about aerosol injection. The team reported the findings in Environmental Research Letters (ERL).

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