As the world struggles with how to keep climate change to the Paris accord goal of below 2C, scientists look to technologies such as solar geoengineering as a way to cool the planet. However, new research shows suddenly ceasing the method could be more disastrous for biodiversity than never starting. Farah Hancock reports.
In 1991, when Mount Pinatubo erupted, 20 million tonnes of sulphur dioxide was propelled into the stratosphere. In the two years that followed, the global average temperate fell by half a degree.
The cooling effect of the eruption is something scientists theorise could be replicated by planes regularly spreading sulphate aerosol. Spread high enough, the tiny particles absorb and reflect sunlight back into space for years.
While planes spraying chemicals to cool the earth may sound like something from a conspiracy theorist’s top 10, solar geoengineering is being taken seriously. Universities in England have collaborated in a 'Stratospheric Particle Injection for Climate Engineering' project since 2010. In the US, Harvard University has a Solar Geoengineering Research Program which has received funding from Bill Gates.
A United Nations report published in October last year says we are a long way off reaching Paris accord targets. Existing national goals will only meet one third of the emissions reduction target.
With emissions targets looking unlikely, geoengineering is receiving increased policy attention as a potential tool to slow climate change.
What’s more, it could be cheaper to implement than cutting emissions.
Professor of applied physics at Harvard University, David Keith, is a long-time proponent of solar geoengineering. He estimates starting an annual spraying programme would take just 10 Gulfstream jets and, “could be deployed in a few years for the price of a Hollywood blockbuster”.
Stopping once you have begun, however, is a not as simple as grounding planes. Stop suddenly and the planet warms up faster than before.
With low set-up cost and a lack of regulatory constraints, starting a programme may be easy. It’s something a single country could do. Stopping once you have begun, however, is not as simple as grounding planes. Stop suddenly and the planet warms up faster than before.
A scenario where solar geoengineering is stopped abruptly after a 50-year programme of spraying is the subject of new research by the University of Maryland, published in Nature Ecology & Evolution.
The research suggests suddenly ceasing solar geoengineering could raise land temperatures by 0.8C in a decade, causing changes in local climates two to four times more rapid than those caused by climate change itself.
The rapid change could be disastrous for biodiversity.
Species will be forced to adapt or move to find a climate they can survive in to avoid extinction. For many species, the climate change will come quicker than they will be able to adapt to, or they will struggle to find somewhere with the right temperature and the right amount of rain.
Areas rich in biodiversity, such as tropical oceans and the Amazon basin, are most likely to be affected negatively.
The research, modelled on sulphate injection at the equator, shows effects for New Zealand. Both the middle of the North Island and the top of the South Island would experience a spike of climate change of at least double the rate of that with no solar engineering intervention.
The research notes more work needs to be done to understand exactly which species would be the most likely to be impacted, but birds, fish, reptiles and to some extent, mammals, would be affected. Different species may also adapt and move at different rates, effectively collapsing established ecosystems.
The research concludes aggressive cuts in emissions remain the best way to avoid biodiversity loss and calls for extreme caution in the development of any policy around geoengineering.
Keith, the Harvard University advocate for geoengineering, says he believes emission cuts will only moderate, not reverse, climate change and we should be moving towards solar geoengineering as quickly as possible.
He is planning to conduct small-scale tests this year, using a hot air balloon, to spread various substances.
In his book, A case for climate engineering, Keith says it is a hard choice:
“Deliberately adding one pollutant to temporarily counter another is a brutally ugly technical fix, yet that is the essence of the suggestion that sulphur be injected into the stratosphere to limit the damage of the carbon we pumped into the air.”