- Nations meeting to advance action on climate change at COP27 in Egypt know we’re headed for dangerous climate impacts.
- UNEP 2022 emissions gap report that there is no longer a ‘credible pathway’ to keep global warming below 1.5°C based on 2030 commitments.
- Risks of geoengineering are unknown and potentially hazardous.
A 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.
Run Up To Clean Energy
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: modeling 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 gasses 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.
A Potent Solution
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).
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 sulfate aerosols in the stratosphere, or to increase the reflectivity of clouds (cloud whitening) or surface objects like rooftops.
In theory, these approaches could rapidly cool global temperatures—especially the dispersal of sulphate aerosols, whose effect would be somewhat like what happens naturally from massive volcanic plumes. The eruption of Mount Pinatubo in mid-1991, for example, is estimated to have cooled global temperatures by 0.5°C for two years.
The Dangers That Lie
The danger with these approaches is that deep uncertainty exists about their impacts. They could drive severe consequences that—like global warming itself—don’t respect borders. Dimming sunlight with sulphate aerosols could diminish crop productivity while altering precipitation patterns and increasing the acidity of rainfall, all of which would further stress climate-change-affected regions and the global food system.
Other geoengineering approaches could backfire in other ways. For example, deploying a massive number of glass beads to enable the Arctic to reflect more sunlight could instead trap more sunlight as heat, likely resulting in faster melting of sea ice.
Scientific uncertainty about the use and consequences of geoengineering is a legitimate concern, but there are barriers even to studying it (particularly in the case of solar radiation management). The UN Convention on Biological Diversity has banned all but small-scale geoengineering experiments for over a decade. Earlier this year, a group of concerned scientists and governance experts published an open letter calling for a total ban on solar geoengineering on the grounds that its impacts can never be fully understood or equitably governed in the international system.
Multilateral institutions are our best hope for governing geoengineering. As ineffective as they may seem at managing our shared atmosphere, particularly as we return to a multipolar world, they’re the reason we’ve avoided the worst-case emissions scenario—and are recovering our ozone layer. Energy markets and economic self-interest may drive the transition, but it was global scientific consensus and the UN that established the knowledge, imperative and targets driving global efforts.
There should be no doubt that geoengineering is an absolute last resort we should fear—for a worst-case scenario we can still avoid. Of course, we need to rapidly reduce emissions to avoid dangerous warming in the first place and redouble investments in adaptation.
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