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Can solar geoengineering save us from climate change?

  • Is the idea of stopping global warming by spraying aerosol gases in the air just a pie in the sky?
  • Here’s a Lounge explainer on solar geoengineering

Solar geoengineering seeks to reflect solar energy back into space.
Solar geoengineering seeks to reflect solar energy back into space. (Photo: Alamy)

One of my favourite quotes on using solar geoengineering to combat global warming comes from agricultural economist Jonathan Proctor. Speaking to The Atlantic in August 2018, he said: “You’re in an arena with a big bear. And the question is: Should you throw a lion into the arena? You know, maybe they’ll fight and kill each other. Or maybe they’ll just both kill you." The bear is, of course, climate change, and the lion is geoengineering.

Although the idea of a grand technological solution to combat rising temperatures has been mooted for over 40 years (including a proposal in 1997 to put giant mirrors in space), geoengineering is catching the public imagination, both as a backup to climate change mitigation and as a quick-fix alternative to the messy business of reducing carbon emissions.

The Pinatubo eruption in 1991.
The Pinatubo eruption in 1991. (Photo: Alamy)

But what is solar geoengineering? Simply put, it is the process of spraying the Earth’s atmosphere with aerosol gas particles. The hope is that the particles would layer the atmosphere and reflect some portion of solar energy back into space, thus bringing about global cooling. Advocates of geoengineering often compare it to the effect of the Pinatubo volcano eruption in 1991 in the Philippines. This cataclysmic eruption had ejected 20 million tonnes of sulphur dioxide, an aerosol gas, 35km into the air. The dispersal of this mammoth gas cloud around the world led to global temperatures dropping by 0.5 degrees Celsius between 1991-93. What if, ask geoengineering backers, we mimic this and thus fight climate change?

Nor is spraying aerosols into the atmosphere the only method. There’s also cloud brightening, something researchers seem to be quite interested in. In this scenario, high-altitude clouds are sprayed with sea water. The high salt content would, theoretically, increase the clouds’ albedo effect, i.e. make them more reflective. This would have a similar effect of reflecting the sun’s rays and ushering in a cooling of temperatures.

Key geoengineering research.
Key geoengineering research.

If all this sounds too good to be true, that’s because it is. According to Jane Flegal, programme officer for environment at the New York-based Bernard And Anne Spitzer Charitable Trust, research in geoengineering is in a very early stage. “This is basically a twinkle in the eye of a handful of scientists," she said on the climate change podcast Warm Regards recently. Flegal is in charge of grant-making for climate change research and used to be a senior policy analyst for Energy Project of the Bipartisan Policy Centre, a Washington, D.C.-based think tank. In the podcast, Flegal points out that very little research has been conducted on solar geoengineering. A funding report prepared by Harvard’s solar geoengineering research program, points out that global funding in 2018 was a little over $8 million (around 56 crore now), a negligible amount. Furthermore, most of this funding went to social scientific research and climate modelling. Very few physical scientists are working on geoengineering research.

Then there’s the small matter of ethics. If the Pinatubo eruption was good for global cooling, it was terrible for global agriculture. According to Proctor’s research, which was published in Nature last year, global corn yields had taken a hit of 9.3%, while rice and wheat yields declined by 4.8% in Pinatubo’s wake. In fact, the paper, which took this data to simulate different future Earth scenarios, with or without solar geoengineering, found that the gains and the setbacks mostly cancelled each other out.

However, some others have a more rosy view of things. A paper, published in Nature Climate Change, made waves in March with the declaration that solar geoengineering is wholly positive. David Keith, a Harvard physicist, and his team carried out computer simulations based on a general dimming of sunlight and reported that the Earth would benefit in such a scenario, without any negative outcomes. But this assertion was met with criticism. While scientists agreed that the research is important, they warned that the positive outcomes of a perfectly controlled computer simulation cannot be taken as the final word on the subject. Keith has himself asserted the need for more research.

Even a physical experiment of injecting aerosols into the atmosphere is fraught with risks, not to mention that it isn’t currently possible to do so. The closest we have come to it is the Stratospheric Particle Injection for Climate Engineering (SPICE) project, co-funded by the UK government’s engineering and physical sciences research council (EPSRC), in 2010. Although a test was planned the following year, it was cancelled after concerns were raised about the lack of government regulation regarding a project with so many unknown results.

If we are planning on toying with the stratosphere, there can’t be any margin for error. And according to an article, Developing Countries Must Lead On Geoengineering Research, in Nature last year, right now the margin for error is huge. Written by A. Atiq Rahman, executive director of the Bangladesh Centre for Advanced Studies; Paulo Artaxo, professor of environmental physics, São Paulo; Asfawossen Asrat, professor of geology from Addis Ababa; and Andy Parker, project director of the Solar Radiation Management Governance Initiative, Bristol, the article stated that “developing countries have most to gain or lose" from solar geoengineering. The authors cautioned that such technology is “outlandish and unsettling", but that modelling research suggests that if successful, such experiments could reduce some of the worst outcomes of climate change.

Yet, as the authors state, even successful geoengineering would be a stopgap, much like Pinatubo’s effect was: “But solar geoengineering is no panacea; it could compound some risks of climate change. It would only mask the warming effect of greenhouse gases. Ocean acidification would still pose a threat to marine life if carbon-dioxide emissions were not slashed. Sulphur dioxide might delay ozone regeneration in the stratosphere. And whichever aerosol was used to filter out sunlight, more research would be needed on its impacts on health and the environment." And which country or organization can take the lead on a “global" technology, the authors ask. Ultimately, it’s no substitute for cutting carbon emissions and preparing adaptation plans.

It’s probably better to think of solar geoengineering as part of a portfolio of actions to deal with the risks posed by climate change. Flegal says on Warm Regards that even a best case scenario, like “getting emissions to zero yesterday, only solves part of the problem". She says that solar geoengineering techniques can be used for “peak shaving (of climate impacts) or risk minimization in the context of a world with sharply reduced emissions and increased adaptive capacity".

Right now, the use of technology is an attractive idea, and some day in the future, with enough research, better trials and strict national and international codes of regulation, it might even be possible. But it’s not going to save the world from global warming.

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