Geoengineering - using technology to bring about global cooling - has some attraction as a tool to offset climate change. But researchers from the US say deliberately changing Earth's climate is more dangerous to ecosystems than global warming is likely to be. It comes down to speed: the pace of global warming is slow enough to give some species time to adapt, but geoengineering the stratosphere has no such limits - it's fast and could leave some species unable to recover, greatly increasing the risk of extinction. In an accompanying comment piece, a UK academic notes that the risk is much higher if we use a geoengineering technique and then abruptly stop it - this is also likely to lead to worldwide droughts, floods and other extreme weather.

Media Release

Springer Nature

Once started, geoengineering is too dangerous to stop

Solar geoengineering is a potential way of reversing the physical effects of climate change, but if it is attempted and then stopped, the consequences for biodiversity could be more severe than those of climate change itself, according to new research published in Nature Ecology & Evolution.

Large-scale removal of carbon dioxide from the atmosphere and the use of aerosols to reflect sunlight back to space (solar geoengineering) have been suggested as potential strategies to counteract greenhouse gas emissions in order to achieve the 2 °C temperature target set by the Paris Agreement.

Christopher Trisos and colleagues investigate the consequences that the implementation and subsequent sudden termination of solar geoengineering could have on global biodiversity. They compare changes in temperature and precipitation under a climate scenario in which geoengineering runs from 2020 until 2070 to a scenario with no geoengineering and intermediate emissions. They find that rapid implementation of geoengineering has a mix of positive and negative effects on biodiversity, but that abrupt termination causes changes in local climates that are 2–4 times more rapid than those caused by climate change itself. They find that, in many cases, rapid geoengineering threatens ecosystems by forcing species to move in one direction to maintain similar temperature conditions and a different direction for similar precipitation conditions. Biodiversity-rich areas, such as tropical oceans and the Amazon basin, are particularly likely to be affected negatively.

These results indicate that geoengineering, and, in particular, its rapid termination, could cause irreversible loss of biodiversity. In an accompanying News & Views, Phil Williamson writes that the political contentiousness of geoengineering means that rapid initiation or termination are very real possibilities. With negative emissions also having potential consequences for biodiversity, due to the land required for bioenergy, he argues that far more ambitious cuts in emissions are needed to avoid species extinctions.