GEOENGINEERINGAs the Planet Warms, Risks of Geoengineering the Climate Mount
Because a climate-disrupted future remains possible, another danger needs our attention. As the impacts of warming become more extreme, countries are more likely to turn to riskier measures to combat them, including geoengineering.
Nations meeting to advance action on climate change at COP27 in Egypt know we’re headed for dangerous climate impacts. The UN Environment Programme confirmed in its 2022 emissions gap report that there is no longer a ‘credible pathway’ to keep global warming below 1.5°C based on 2030 commitments. The report, titled The Closing Window, suggests that we may still have a shot at keeping warming to 2.0°C, but only if all countries fully meet their net-zero pledges. That’s far from guaranteed or likely given the lack of detail in those pledges. We’re already seeing extreme climate events annually—but even more dangerous impacts are locked in.
The good news is that our efforts to deploy clean energy have succeeded enough to rule out the worst-case projected emissions scenarios and it’s now unlikely that we’ll reach catastrophic warming beyond 4.0°C. There’s one important caveat: modelling suggests that any warming over 1.5°C will increase the risk of self-reinforcing tipping points in the global climate system. Tipping points are temperature thresholds at which significant greenhouse gases can be released suddenly, greatly amplifying global warming—for example, a release of frozen stores of carbon dioxide and methane gas from thawing Arctic permafrost.
Because a climate-disrupted future remains possible, another danger needs our attention. As the impacts of warming become more extreme, countries are more likely to turn to riskier measures to combat them, including geoengineering.
Geoengineering can entail modifying local weather conditions (such as seeding clouds to change rainfall), removing carbon dioxide from the atmosphere (separating it out and storing it) or managing solar radiation (reducing the amount of sunlight that can get trapped as heat in the atmosphere). These options have been discussed in climate circles for many years—at various times considered a last resort, a moral hazard that could delay decarbonisation of economies, or generally a dystopian nightmare.
Solar radiation management is the most troubling geoengineering idea. The objective is to block sunlight entirely by deploying satellite sunshades between the earth and the sun, to dim the skies by dispersing reflective sulphate aerosols in the stratosphere, or to increase the reflectivity of clouds (cloud whitening) or surface objects like rooftops (or, in an extreme case, glass beads scattered across the Arctic).
