Humanity has managed to stabilize its carbon emissions, but they have yet to start decreasing. It looks increasingly likely that we will be emitting enough to commit to at least 1.5°C of warming – and we need to act quickly to avoid going beyond 2°C. alternatives such as removing carbon dioxide from the air or geoengineering to reduce the amount of incident sunlight.
Of the two, geoengineering comes with the longest list of unknowns, with a recent report from the National Academies of Science stating, “Scientific understanding of many aspects of solar geoengineering technologies remains limited, including how to mitigate extreme weather events, agriculture, can affect natural ecosystems, or human health.”
So, of course, some Silicon Valley types decided to go ahead and start a startup company that would offer geoengineering for a fee. The company claims to offer warming offsets despite the significant unknowns related to geoengineering. And it’s even worse than that sounds; based on an article in MIT Technology Review, the company has already begun launching balloons into the stratosphere, though it is unable to determine whether they actually deploy their payloads.
Engineer the stratosphere?
Geoengineering is generally defined as manipulating the environment in a way that changes the climate. Given that definition, our widespread burning of fossil fuels is a form of geoengineering. But in light of our steadily warming climate, most references to geoengineering are now focused on ways to combat that warming. While a number of possible techniques have been considered, the most practical approach seems to be to cancel out reflective particles in the stratosphere to reduce the amount of sunlight Earth receives.
The general concept has already been validated by volcanoes, which can send sulfur dioxide into the stratosphere and provide cooling in the years following an eruption. For example, the largest eruption of the last century (Mount Pinatubo) cooled the planet for about three years before the sulfur dioxide that placed it in the stratosphere drifted down and then released from the atmosphere in rain.
Sulfur dioxide is cheap and we have the technology needed to take it to the stratosphere without the need for an eruption, so that could be an attractive alternative to the many costly downstream effects of climate change. The “can” largely stems from the extensive unknowns involved in pursuing it. Everything from plants to solar panels depends on sunlight reaching the earth. And while we know the approach works, we still don’t know the details well enough to assign a specific cooling value for a given amount of sulfur dioxide. That sulfur dioxide also forms sulfuric acid when exposed to water, which can cause environmental effects if deployed at the levels needed to change the climate. Finally, our reliance on geoengineering commits us to continue doing it for as long as it takes to reduce atmospheric carbon to manageable levels.
For all those reasons, the scientific community was very hesitant about the idea. The National Academies report mentioned above suggests that there are so many unknowns that any research we do in geoengineering should be designed in a way that doesn’t make it any easier to go ahead and pursue it. “Intentional outdoor experiments that release substances into the atmosphere should only be considered if they can provide critical observations that cannot be provided by laboratory research, modeling or chance experiments — such as volcanic eruptions,” the report’s authors concluded. “Outdoor experiments should be subject to appropriate governance, including permits and impact assessments.”
