Artificially cooling the planet could cause climate chaos

Plans to reverse the effects of global warming by injecting reflective particles into the stratosphere which would mimic the impact of large, tropical volcanic eruptions could have a catastrophic impact on some of the most fragile ecosystems on earth, according to new research led by Angus Ferraro, Dr Andrew Charlton-Perez & Professor Ellie Highwood.

Aerosols in the stratosphere reflect sunlight, reducing the amount of solar energy reaching the surface. This occurs naturally after large volcanic eruptions, such as that of Mount Pinatubo in 1991, which led to a large short-term dip in global temperatures. Aerosols could potentially be artificially sprayed into the upper atmosphere to counteract the effects of climate change. But scientists suggest that such stratospheric aerosol injection, probably the leading candidate for a workable geoengineering scheme, could create significant, harmful side effects by weakening weather systems in the tropics.

However, research published today in Environmental Research Letters and reported by the BBC, the Guardian & the Independent suggests one method of geoengineering: pumping sunlight-reflecting particles into the stratosphere could reduce tropical rainfall by 30%, drying the tropical rainforests in Asia & South America and intensifying periods of drought in Africa. The research also highlights how geoengineering could provide solutions for some regions while causing more problems in others, opening up the possibility of conflict between countries if they were to act unilaterally to alter the climate. In general, countries in northern Europe and parts of Asia would be most likely to benefit, at the expense of parts of Africa, North and South America and South-East Asia.

Dr Andrew Charlton-Perez, one of the co-authors of the research, said: “We have shown that one of the leading candidates for geoengineering could cause a new unintended side-effect over a large part of the planet. The risks from this kind of geo-engineering are huge. A reduction in tropical rainfall of 30% would, for example, quickly dry out Indonesia so much that even the wettest years after a man-made intervention would be equal to drought conditions now. The ecosystems of the tropics are among the most fragile on Earth. We would see changes happening so quickly that there would be little time for people to adapt.”

Co-author of the paper Professor Ellie Highwood, said: “Climate scientists agree that cutting carbon emissions is still necessary to curb the damaging effects of future climate change. However, since such cuts are far from certain to materialise, proponents of geoengineering research argue that whatever the world decides on its carbon emissions, it would be prudent to explore alternatives that might help us in the decades ahead. On the evidence of this research, stratospheric aerosol geoengineering is not providing world leaders with any easy answers to the problem of climate change.”

Angus Ferraro, lead author said: “To reduce global temperatures enough to counter effects of global warming would require a massive injection of aerosol – the small particles that reflect sunlight back into space. This would be equivalent to a volcanic eruption five times the size of that of Mount Pinatubo in 1991 every year. Previous predictions of how stratospheric aerosol injection would affect climate were based on a number of assumptions. By actually modelling what would happen if aerosol were to be pumped into the atmosphere around the equator, we have revealed a new impact of geo-engineering on tropical climate. As well as reflecting some of the incoming energy from the sun and cooling surface temperature, the aerosol also absorbs some of the heat energy coming from the surface which warms the stratosphere. We have shown for the first time that warming the stratosphere makes the troposphere below more stable, weakening upward motion and reducing the amount of rainfall at the surface.”

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