solar geoengineering study

Can solar geoengineering save the world?

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The concept of solar geoengineering—blocking the sun’s radiation to slow Earth’s warming—is no longer just the realm of science fiction. In 2023, the U.S. government and the UN released reports on the topic. Whether or not solar geoengineering can save the world is up for debate, and Tony Harding, an assistant professor in the School of Public Policy, is contributing to the conversation.

Harding is an alumnus of the School of Economics and returned to Georgia Tech after a postdoc at Harvard University. He studies the impact of innovative technology on climate change policy and governance, focusing on solar geoengineering. In the eight years he’s been researching it, Harding said it’s the scale of the conversation that’s changed the most: not what the researchers are speaking about, but who they’re speaking to.

“A lot of people in the climate policy and academic realms were hesitant to talk about solar geoengineering, and I think that’s starting to change,” Harding said. “There’s definitely wider acceptance of at least talking about it, and in that way, pathways to having spaces to talk about it and research funds are opening up.”

As the idea of solar geoengineering picks up steam, Harding invites everyone to join the conversation, starting with learning about what it is, how it works, and whether or not this once-niche proposition really can save the world.

What is solar geoengineering?

The most commonly proposed method of solar geoengineering, which also goes by names such as solar radiation modification or climate intervention, uses sulfate aerosols. When injected into the Earth’s stratosphere, they reflect a small amount of the sun’s radiation—less than 1%—and reduce Earth’s surface temperature.

This option is the most popular, and the one Harding studies, because we have natural examples, he explained. Volcanoes release sulfates when they erupt, and the largest ones are strong enough to push them into the stratosphere.

“So we have evidence from the past that if sulfate aerosols make it up to the stratosphere, there’s a cooling effect,” he said. “This natural analog gives us a bit more belief that it’s going to work at least in some of the ways we expect it to in the real world and not just on a computer.”

The other two types of solar geoengineering researchers consider most seriously are marine cloud brightening to reflect incoming sunlight and Cirrus cloud thinning to let light escape more easily. Each one has pros and cons. For example, marine cloud brightening would only occur over the deepest and darkest parts of the ocean, Harding said, “which would have a non-uniform cooling effect and could lead to certain adverse outcomes.”

Stratospheric aerosol injection has a more uniform distribution and cooling effect that better mimics the warming we’re experiencing. However, it comes with its own concerns, one of which is that the cooling isn’t permanent.

“If something happened to stop the deployment of the aerosols, whether it was for political or technological reasons, we would bounce right back and experience a rapid heating that we’ve never experienced before, and could have catastrophic impacts,” Harding said.

What are the costs and benefits of solar geoengineering?

This question is where Harding’s research makes the most impact. As an economist, he examines the costs and benefits of solar geoengineering to highlight the tradeoffs involved. Harding has published articles on how solar geoengineering could impact other climate change mitigation policies, how it affects income inequality, and the value of reducing uncertainty around solar geoengineering.

US scientists launch world’s biggest solar geoengineering study.

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Research programme will send aerosol injections into the earth’s upper atmosphere to study the risks and benefits of a future solar tech-fix for climate change

 The sun from space
Scientists say the planet could be covered with a solar shield for as little as $10bn a year. 
 US scientists are set to send aerosol injections 20km up into the earth’s stratosphere in the world’s biggest solar geoengineering programme to date, to study the potential of a future tech-fix for global warming.

The $20m (£16m) Harvard University project will launch within weeks and aims to establish whether the technology can safely simulate the atmospheric cooling effects of a volcanic eruption, if a last ditch bid to halt climate change is one day needed.

Scientists hope to complete two small-scale dispersals of first water and then calcium carbonate particles by 2022. Future tests could involve seeding the sky with aluminium oxide – or even diamonds.

Janos Pasztor, Ban Ki-moon’s assistant climate chief at the UN who now leads ageoengineering governance initiative, said that the Harvard scientists would only disperse minimal amounts of compounds in their tests, under strict university controls.

“The real issue here is something much more challenging,” he said “What does moving experimentation from the lab into the atmosphere mean for the overall path towards eventual deployment?”

Geoengineering advocates stress that any attempt at a solar tech fix is years away and should be viewed as a compliment to – not a substitute for – aggressive emissions reductions action.

But the Harvard team, in a promotional video for the project, suggest a redirection of one percent of current climate mitigation funds to geoengineering research, and argue that the planet could be covered with a solar shield for as little as $10bn a year.

Kevin Trenberth, a lead author for the UN’s intergovernmental panel on climate change, said that despair at sluggish climate action, and the rise of Donald Trump were feeding the current tech trend.

“But solar geoengineering is not the answer,” he said. “Cutting incoming solar radiation affects the weather and hydrological cycle. It promotes drought. It destabilizes things and could cause wars. The side effects are many and our models are just not good enough to predict the outcomes”

Natural alterations to the earth’s radiation balance can be short-lasting, but terrifying. A 1991 Mount Pinatubo eruption lowered global temperatures by 0.5C, while the Mount Tambora eruption in 1815 triggered Europe’s ‘year without a summer’, bringing crop failure, famine and disease.

A Met Office study in 2013 said that the dispersal of fine particles in the stratosphere could precipitate a calamitous drought across North Africa.

Frank Keutsch, the Harvard atmospheric sciences professor leading the experiment, said that the deployment of a solar geoengineering system was “a terrifying prospect” that he hoped would never have to be considered. “At the same time, we should never choose ignorance over knowledge in a situation like this,” he said.

“If you put heat into the stratosphere, it may change how much water gets transported from the troposphere to the stratosphere, and the question is how much are you [creating] a domino effect with all kinds of consequences? What we can do to quantify this is to start with lab studies and try to understand the relevant properties of these aerosols.”

Stratospheric controlled perturbation experiments (SCoPEX) are seen as “critical” to this process and the first is planned to spray water molecules into the stratosphere to create a 1km long and 100m wide icy plume, which can be studied by a manoeuvrable flight balloon.

If lab tests are positive, the experiment would then be replicated with a limestone compound which the researchers believe will neither absorb solar or terrestrial radiation, nor deplete the ozone layer.

Bill Gates and other foundations are substantially funding the project, and aerospace companies are thought to be taking a business interest in the technology’s potential.

The programmme’s launch will follow a major conference involving more than 100 scientists, which begins in Washington DC today.

Solar geoengineering’s journey from the fringes of climate science to its mainstream will be sealed at a prestigious Gordon research conference in July, featuring senior figures from the National Oceanic and Atmospheric Administration (NOAA) and Oxford University.

Pasztor says that most scientific observers now see the window to a 1.5C warmed world as “practically gone” and notes that atmospheric carbon dioxide concentrations will continue rising for many decades after the planet has reached a ‘net zero emissions’ point planned for mid-late century.

But critics of solar radiation management approach this as a call to redouble mitigation efforts and guard against the elevation of a questionable Plan B.

“It is appropriate that we spend money on solar geoengineering research,” said Kevin Anderson, the deputy director of the Tyndall Centre for Climate Change Research. “But we also have to aim for 2C with climate mitigation and act as though geoengineering doesn’t work, because it probably won’t.”

Source:https://www.theguardian.com