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Among the long list of strategies suggested by scientists to combat global warming, solar geoengineering could be one of the most controversial.
At least in theory.
The idea is relatively simple: spray reflective aerosols into the atmosphere to project solar radiation away from the planet and cool the climate. However, some modeling studies suggest that the strategy could have unintended consequences, including precipitation, hydrology, storms, and other weather events.
The concept is strictly a hypothetical suggestion for the moment. But this attracts attention as a possible complement to other forms of climate action. Global efforts to reduce greenhouse gas emissions are increasingly lagging behind measures needed by scientists to prevent catastrophic levels of future warming.
New research can now alleviate some of the fears about the side effects of solar geoengineering – or at least encourage more research on the subject.
A study published in Nature Climate change This week, it is suggested that keeping geoengineering within limits should avoid undesirable consequences for factors such as water availability, storms and extreme precipitation. The research is based on a scenario in which the amount of solar geoengineering deployed could only offset half – not all – of the warming that would occur if carbon dioxide levels in the atmosphere doubled.
"Many previous studies have been devoted to this question, so could you make up for it," said Peter Irvine, lead author of the study, a climate and geoengineering researcher at Harvard University. "And some of the results that they got were the result of doing too much in one way, going a little too far."
Studies that have assumed more intense levels of solar geoengineering have tended to show that undesirable side effects may appear. Some concerns include the risk that extreme rainfall and flooding will increase in some areas, while others will experience increased drought, and that these effects could be even more severe than the expected changes if nothing was done. to fight against climate change.
In contrast, in the "half-warming" scenario used in the new study, research suggests that solar geoengineering should not worsen water-related changes that they would not be without.
According to co-author David Keith, a Harvard engineer and geoengineering expert, "it's the dose that makes the poison".
The study is based on a high-resolution model particularly suitable for simulating hurricanes and extreme precipitation. The authors examined a handful of different potential climate outcomes, including average and maximum temperatures, maximum annual precipitation, and total water availability for a given region, defined as the amount of precipitation falling relative to the amount of rainfall. evaporated water from the area.
They assessed results region by region from around the world, dividing the world into segments identical to those used by the Intergovernmental Panel on Climate Change in its analyzes of regional climate effects. In each case, they assessed whether the effect of the climate was exacerbated by solar geo-engineering, that is, aggravated by unmitigated climate change and the lack of climate change. geoengineering.
They found that none of these variables had been compounded by solar geoengineering.
The researchers also examined globally the intensity of hurricanes and typhoons. They found that on a global scale, the intensity of the storms would not be aggravated. In fact, geoengineering would largely offset the effect of climate change on hurricane intensity.
These discoveries are not completely new, according to Keith. Previous studies suggest similar results if the appropriate level of geoengineering is applied. This is when one assumes that the deployment levels are higher than the negative consequences really begin to appear, he says.
"It's not as if our study was canceling out what previous studies had revealed. In fact, it does a better job of reinforcing what previous studies have discovered, "he told E & E News. "But I hope this will help raise awareness of the fact that there is a big gap between the content of the studies and what people are talking about."
Future uncertain
The new research "actually confirms that a moderate solar geoengineering scenario would improve temperature and precipitation changes in most regions," said Anthony Jones, a postdoctoral researcher on aerosols and climate at the University. Exeter, in an email. And this reinforces the need for further research on the issue, he added.
Nevertheless, the study is not a completely realistic description of potential solar geoengineering scenarios – a point acknowledged by the researchers.
First, the study simulates the effects of solar geoengineering by simply adjusting the amount of solar radiation received by the Earth's surface. It does not exactly reproduce the effects of aerosols in the air, which could have additional side effects, such as the warming of some parts of the atmosphere, the change in atmospheric circulation or the alteration of the ozone layer according to Alan Robock, aerosol expert and climatologist. Rutgers University.
It would be "premature" to conclude that no region of the planet would experience climatic effects exacerbated by geo-engineering, even in a half-warming scenario, the study's researchers conclude. But this calls into question the idea that such results are inevitable or that they always outweigh the benefits.
Some experts remain cautious.
"I do not agree that no area will be significantly degraded by a solar geo-engineering scenario," Robock said in an email. "Worse compared to what? If we start taking mitigation action now, that is to say that we will quickly reduce our CO2 emissions by switching from wind energy to solar energy, we we will carry much better than an unchanged future or with geoengineering. "
The authors of the new study are keen to note that geoengineering is not intended to replace the reduction of greenhouse gas emissions. It could rather be a complement to more traditional forms of climate action if it started to give the impression that these efforts were not going fast enough.
Keith said that it was justified to fear that the technology would be used inappropriately, for example, as a political justification for the postponement of other forms of action for the climate.
"But I do not think it's a justification for not knowing more about something that could potentially significantly reduce risk, especially for the world's most vulnerable people," he added.
Questions about the future of geoengineering research may well be at a turning point. Scientists and policy-makers around the world are beginning to discuss how future geoengineering experiments, including potential field experiments, should be regulated and regulated to ensure that they are conducted in a safe and ethical manner.
Keith himself is involved in organizing what could become the first geoengineering field test. The project, called SCoPEx, aims to study the effects of aerosols in the stratosphere with the help of a high altitude balloon. This will likely begin with water, but possibly with other types of materials proposed for use in geoengineering.
Experiments, still in the planning stage, would be on such a small scale that they would not pose any foreseeable risk, the organizers said. But the idea allowed for discussions about what could happen if researchers were interested in larger and more ambitious geoengineering experiments, or if the technology reached the point where governments could actually consider deploying it. .
In October, the National Academy of Sciences announced the creation of a committee to study solar geoengineering and develop a set of recommendations on how to manage future experiments on the subject. ground (ClimateWireOctober 26, 2018). Last month, the NAS announced the appointment of the committee, co-chaired by Susan Biniaz of the United Nations Foundation and Center for Climate and Energy Solutions and Christopher Field of the Stanford Woods Institute for the Environment. .
Meanwhile, the Swiss government and 10 other countries have drafted a resolution asking the United Nations Environment Program to prepare an assessment of the state of various forms of geoengineering, including solar geoengineering. The resolution is expected to be presented at the United Nations Environment Assembly session in Nairobi this week.
Other organizations have also encouraged the United Nations to begin considering recommendations for the management of geoengineering. In May, Carnegie's Geo Geoengineering Governance Initiative made a presentation to a US Environmental Program Committee, highlighting the need for an international agreement on the regulation of environmental technology. geoengineering (ClimateWireMay 23, 2018).
Such initiatives reflect the growing interest of scientists and policymakers in the international community in the future of this technology, however uncertain it may be. For now, Keith said, "I do not think you can justify suppressing research and knowledge about solar geoengineering" based solely on fears of political abuse.
And even if technology becomes viable on a large scale in the future, mankind will still have to commit to completely eliminating greenhouse gas emissions, according to Keith.
"Regardless of the quality of solar geoengineering, you can not continue to release CO2 into the atmosphere forever and hope for a stable climate," he said.
Reproduced from Climatewire with the permission of E & E News. E & E provides daily coverage of vital energy and environmental information on www.eenews.net.
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