Planetary securityGeoengineering measures to cool the planet would cause climate chaos
Geoengineering — the intentional manipulation of the climate to counter the effect of global warming — is being proposed as a last-ditch way to deal with the problems of climate change. New research suggests geoengineering could cause massive changes to rainfall patterns around the equator, drying the tropical rainforests in South America and Asia, and intensifying periods of drought in Africa.
Plans to reverse the effects of global warming by mimicking big volcanic eruptions would have a catastrophic impact on some of the most fragile ecosystems on Earth, new research has shown.
Geoengineering — the intentional manipulation of the climate to counter the effect of global warming — is being proposed as a last-ditch way to deal with the problems of climate change.
A University of Exeter release reports that new research co-authored by University of Exeter expert Angus Ferraro suggests geoengineering could cause massive changes to rainfall patterns around the equator, drying the tropical rainforests in South America and Asia, and intensifying periods of drought in Africa.
The research also highlights how global 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.
Geoengineering is a hot topic. Governments and the world’s leading climate scientists on the UN’s Intergovernmental Panel on Climate Change (IPCC) discussed the prospect of artificially cooling the climate at its meeting in Stockholm in September 2013.
Aerosols in the stratosphere reflect sunlight, reducing the amount of solar energy reaching the surface. This occurs naturally after big 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.
The researchers suggest, however, that such stratospheric aerosol injection, probably the leading candidate for a workable geo-engineering scheme, would create significant, harmful side effects by weakening weather systems in the tropics.
The research was carried out at the University of Reading’s Department of Meteorology, one of the world’s leading centres for the study of weather and climate.
Angus, who has recently joined the University of Exeter’s Mathematics department in the College of Mathematics, Engineering and Physical Sciences, 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.”
Angus co-authored the research with academics from the University of Reading as part of a NERC-funded research project, with collaborators Dr. Andrew Charlton-Perez and Professor Ellie Highwood.
Dr. Charlton-Perez 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 percent 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.
“Discussion of geoengineering often prompts heated debate, but very often there is a lack of understanding of what putting large amounts of aerosol in the stratosphere will do to the complex climate system. Our findings should help to fill in some of the gaps about one of the leading candidates.”
Professor Ellie Highwood added: “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 geo-engineering 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 geo-engineering is not providing world leaders with any easy answers to the problem of climate change.”
The research is the first to highlight these changes to the tropical circulation.
— Read more in Angus J Ferraro et al., “Weakened tropical circulation and reduced precipitation in response to geoengineering,” Environmental Research Letters 9, no. 1 (8 January 2014) (doi:10.1088/1748-9326/9/1/014001)
