Last month, new research from Harvard and Yale led to a flurry of news claiming scientists were proposing to ‘dim the Sun’ in an “ingenious but as-yet-unproven way to tackle climate change”.
Only, they weren’t. As other outlets made clear, the paper was actually an analysis of whether solar geoengineering is technically and economically feasible, nothing more.
The funny thing is, though, those overblown headlines almost did get it right after all, even if only by accident.
As it happens, other Harvard scientists are indeed moving ahead with a groundbreaking plan to test the effects of solar geoengineering in the skies above our heads, and their US$3 million experiment could begin as early as next year.
The project – called the Stratospheric Controlled Perturbation Experiment (SCoPEx) – is part of Harvard’s Solar Geoengineering Research Program.
While most studies looking at the effects of spraying chemicals into the atmosphere to cool the planet rely on computer simulations to test their hypotheses, SCoPEx will conduct its testing in the real world.
In the experiment, a high-altitude balloon will fly up to the stratosphere, at an altitude of about 20 kilometres, and release a small aerosol plume of calcium carbonate.
Once the chemical payload is released, it’s expected to disperse into a perturbed air mass about 1 kilometre long and 100 metres in diameter. The balloon will then fly back and forth through this cloud repeatedly for about 24 hours, analysing the particles’ behaviour and evolution in the sky.
The reason we might want to do this is to see whether sunlight-reflecting particles in the atmosphere could cool down the surface of the planet, in an intentionally contrived recreation of the effects of a volcano eruption – most notably, the observed global cooling effects of the Mount Pinatubo eruption in 1991.
But solar geoengineering is not without its controversies. Some studies suggest spraying huge amounts of sunlight-reflecting particles into the atmosphere could have grave consequences, leading to unintended issues for things like crops, weather patterns, or the ozone layer.
The ozone layer in particular is one of the reasons the team behind SCoPEx is working with calcium carbonate – because their previous research indicated it could be the safest in terms of stratospheric chemistry.
That said, there’s still a huge amount we don’t know about what solar geoengineering might unleash, which is all the more reason to conduct small-scale experiments like SCoPEx, which will only release about the same amount of particulate as one minute of commercial airliner emissions.
“There are all of these downstream effects that we don’t fully understand,” atmospheric chemist and SCoPEx principal investigator Frank Keutsch told Nature.
As always, even if the experiments prove successful – and demonstrate that solar geoengineering is something we could potentially roll out on a larger scale – it’s not a silver bullet for global warming.
Drastically reducing existing levels of carbon emissions should still be humanity’s first response to climate change, because that’s the root cause of our heat-trapping problems – and solar geoengineering won’t be able to help other related issues, like ocean acidification.
“Solar reengineering is a supplement, and in the end we still have to cut emissions,” one of the team, applied physicist David Keith, said in 2016.
While the world takes care of that, scientists will be testing just what this supplement is capable of, and from the sounds of it, we won’t have to wait too long to find out if ‘dimming the Sun’ can help us.
A 2014 paper on the SCoPEx research is available here.