Scientists Preparing Experiments to Dim the Sun

Can a Hail Mary to stave off climate change by dimming the Sun work? Scientists in the UK are poised to find out. The Telegraph reports that the British government is expected to greenlight a bevy of solar geoengineering experiments in the coming weeks, which will explore techniques ranging from injecting aerosols into the atmosphere to brightening clouds to reflect sunlight.

The experiments will be funded to the tune of roughly $66.5 million by the Advanced Research and Invention Agency, making the UK one of the biggest funders of solar geoengineering research in the world, according to the Guardian. This stands in contrast to the US, where a number of high-profile solar geoengineering experiments have been shut down while some states consider banning future attempts. 

Such dramatic measures to respond to climate change remain extremely controversial in the scientific community — for good reason — but as we race towards critical warming tipping points past which the effects of climate change are believed to be irreversible, some argue that we should be exploring all our options. 

"The uncomfortable truth is that our current warming trajectory makes a number of such tipping points distinctly possible over the next century," Mark Symes, programmer director for ARIA told the Guardian. "This has driven increased interest in approaches that might actively cool the world in a short time frame in order to avoid those tipping points. Having spoken to hundreds of researchers, we reached the conclusion that a critical missing part of our understanding was real world, physical data."

The leading proposed method for reducing our planet's dose of solar radiation is through stratospheric aerosol injection, which involves releasing massive amounts of small particles — the most popular candidate being sulfur dioxide — into the atmosphere, where they would reflect some sunlight back into space.

Another known as marine cloud brightening proposes we enhance nature's greatest source of shade, clouds, by spraying them with sea salt aerosols that promote water droplet formation to make them denser and bounce back more sunlight. The flip side of that is a more fringe technique called cirrus cloud thinning, which suggests thinning the high-altitude clouds because they trap more sunlight than they reflect.

As easy as it is to imagine any of these going catastrophically wrong — not to mention their potential to distract from the fact that we must dramatically curb greenhouse gas emissions — there is some real-world evidence suggesting that these measures could work, according to Jim Haywood, a professor of atmospheric science at the University of Exeter. Scientists have observed how the gigantic clouds of sulfur released by volcanic eruptions have led to global temperature drops — evidence in favor of aerosol injection — and similarly how the ashy plumes brightened clouds while also increasing their size — ditto cloud brightening. 

Additional research has shown that a sharp dropoff in shipping fumes due to international regulations ironically caused a spike in global temperatures. But how scientists interpret that result is a glass half-empty half-full situation. On the one hand, it suggests that deliberately releasing aerosols could help measurably cool our planet. On the other, critics argue that it's a foreboding example of how solar geoengineering could go wrong by leading to a "termination shock," in which the planet rapidly heats up again the moment we stop releasing aerosols.

"At the moment, all of these ideas need to remain on the table, because otherwise climate change in the coming decades could be extremely damaging," Haywood told the Guardian. "Recent global temperatures have been a real wake-up call."

More on climate change: Scientists Activate Facility to Suck Carbon Directly Out of the Ocean

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