There are several ways to respond to the current climate change crisis.

One is to limit the burning of fossil fuels and move towards a renewable energy system but that has proven to be a slow endeavour. 

Amid this international collaborative impotence, more and more discussions lean towards ways to engineer our way out of the crisis.

One way is to scatter sunlight through the injection of sulphate particles in the atmosphere. The technique is even mentioned in the Intergovernmental Panel on Climate Change's 2013 Summary for Policymakers.

Neither effective nor feasible?
In the current issue of Nature Climate Change an international team of scientists including centre researchers Anne-Sophie Crépin, Gretchen Daily, Carl Folke and Victor Galaz, conclude that this kind of geoengineering is unlikely to be the game-changer some people expect it to be.

Simply put, the many problems associated with geoengineering, including its inability to address every climate emergency, the many possible negative environmental side effects, and the geopolitical problems that would be triggered, suggest that the need to address the root causes is as strong as ever.

"If anything, the prospect of geoengineering should strengthen resolve to tackle climate change by limiting atmospheric concentrations of greenhouse gases," the authors argue.

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Helping some, harming others
Putting sulphate aerosols in the stratosphere to scatter sunlight could very well reduce temperature in the lower atmosphere in a relatively quick and inexpensive way. It could even be done unilaterally, without the need for international cooperation. This might sound uncomplicated, but that is ironically also one of geoengineering's major problems. While it might limit global warming and help some countries it is likely to harm others, for example by altering the monsoons.

"The use of stratospheric aerosols poses a number of huge challenges for governance. Even though 'losers' were to be compensated for their losses it would be more or less impossible to attribute particular changes to climate engineering rather than to natural variation," the authors write.

Geoengineering would also have a range of environmental side-effects unrelated to the climate. A planet disturbed by both elevated CO2 concentrations and geoengineering would no doubt be very different. The effects on ecosystems will be complex and spatially variable, with implications for food production, freshwater supplies, and human health, creating both winners and losers.

Human behaviour will also matter. For example, even though agricultural yields for certain crops might increase on a global scale, the local effects will probably be highly variable, with implications for land-use change, crop selection, and food prices.

The risk of addiction
In the article, the use of geoengineering as a "stop-gap" is also discussed. This implies to deploy stratospheric aerosol injection while more effort is put into reducing emissions. Once concentrations return to 'safe' levels, geoengineering could be scaled back and eventually stopped.

If, however, such geoengineering were used over a number of decades, and greenhouse gases concentrations continued to rise, turning geoengineering off abruptly would cause rapid climate change.

"The bigger risk to using geoengineering, we believe, is not that countries will turn it off abruptly but that, having begun to use it, they will continue to use it and may even become addicted to it."

Such "addiction" could imply that societies adapt to the combined effects of both climate change and geoengineering, for example by limiting sea water to protect sensitive coral ecosystems from ocean acidification and genetically engineering crops to benefit both from higher CO2 concentrations and more diffused light.

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