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A new study has confirmed that artificially cooling the Earth through technologies that reduce incoming sunlight would not be enough to prevent extreme warming for long periods of time, unless associated with cuts in greenhouse gases.
The research uses modeling to examine what would happen if, hypothetically, greenhouse gases were left to spiral over the next century while “solar geoengineering” was used to reduce global warming.
Solar geoengineering is a term used to describe a largely still hypothetical set of technologies that would reflect sunlight away from Earth in order to reduce global temperature rise and some of its associated impacts.
The most commonly proposed method of achieving this would be the release of reflective particles, known as aerosols, into the stratosphere. Once released, the aerosols would form a protective sheath around Earth, scientists expect, reflecting incoming sunlight.
The idea has a natural analogue in volcanic eruptions, which in the past have temporarily cooled global temperatures. When a volcano erupts, it often sends a cloud of ash up into the atmosphere, which can lead to the production of aerosols that reflect sunlight.
Although solar geoengineering would theoretically be able to lower the temperature rise, it would not be able to directly address its root cause, which are greenhouse gas emissions released by humans.
The new research, published in Proceedings of the National Academy of Sciences, found that hypothetically, solar geoengineering would not be effective in reducing warming if greenhouse gases were allowed to rise to extremely high levels.
This is because extremely high levels of greenhouse gases in the atmosphere would cause the low clouds, known as stratocumulus, to thin out, which would eventually break apart.
The stratocumulus clouds themselves cool the Earth by shading large portions of its surface from sunlight. If the straocomumlus clouds covering subtropical oceans were to break completely, they could lead to an additional 5 ° C of global warming, the research says.
When a volcano erupts, it often sends a cloud of ash up into the atmosphere, which can lead to the production of aerosols that reflect sunlight.
(Getty)
“Stratocumulus clouds thin as greenhouse gas concentrations increase and their reflection in sunlight decreases,” said study lead author Prof Tapio Schneider, a climate scientist at the California Institute of Technology. The independent.
“Solar geoengineering may not be safe to prevent severe warming if it continues for more than a century and greenhouse gas emissions continue to rise during that time.”
The research found that, in simulations that include solar geoengineering, subtropical stratocumulus clouds break down when carbon dioxide levels in the atmosphere exceed 1,700 parts per million (ppm). This is more than four times the current level.
“I think the paper provides yet another argument as to why solar geoengineering cannot be a ‘get out of jail’ card that leaves us off the hook for the need to reduce our CO2 emissions; we can’t just burn all the fossil fuels into the ground and solve the problem with solar geoengineering, ”said Dr. Doug MacMartin, a senior researcher at Cornell University in New York who was not involved in the paper. The independent.
“It is equally important to point out, however, that the scenario they are considering is indeed quite extreme.”
Carbon dioxide levels would only reach 1,700 ppm in an “extremely worst case scenario” where little is done to address emissions beyond the 21st century, added Dr Pete Irvine, a lecturer in climate change at University College London, also. ‘he not involved. in the studio.
So far, most solar geoengineering research has been conducted using computer simulations, meaning little is known about its potential real-world implications.
However, in the future, a team of scientists from Harvard University plans to carry out one of the first field tests of solar geoengineering.
The project, known as the Stratospheric Controlled Perturbation Experiment (SCoPEx), plans to use a high-altitude balloon to release an aerosol-containing package 20km into the stratosphere.
The amount of aerosol released will not be enough to have a cooling effect on the planet, the researchers say, but it could allow scientists to collect data on how aerosol particles interact with air.
Scientists had initially announced their intention to conduct the experiment in 2017, but the project has so far been delayed by “technical problems,” according to the project’s blog.
Previous research has highlighted various social and ethical considerations associated with solar geoengineering.
One is, if the technology were to be developed, it could be perceived as a “quick fix” to the climate crisis, leading countries to pause on their commitments to reduce greenhouse gas emissions. Another is that the technology could be misused by individual actors or states with malicious intent.
“The question of whether to pursue solar geoengineering is not purely scientific, but involves governance, ethical and political issues,” said prof. Schneider.
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