Geoengineering is the deliberate, large-scale manipulation of the climate in the hope of regulating global temperature.

A wide variety of technologies are commonly divided into solar radiation management (SRM) techniques such as spraying sulphates into the upper atmosphere on an ongoing basis to simulate the cooling effects of volcanoes, and carbon dioxide removal (CDR) such as carbon capture and storage.

Other proposals range from the possible to bizarre and dangerous, and include marine cloud brightening, space-based mirrors, terrestrial and ocean surface-whitening, and a giant sunshade in the sky.

Unintended and uncontrollable

Scientists have recently proposed mammoth engineering projects in Greenland and Antarctica to slow down the disintegration of glaciers and prevent inundation of low-lying, densely populated areas in Bangladesh, Japan and the Netherlands.

These include underwater giant walls, artificial islands and huge pumping stations to channel cold water into the bases of glaciers to stop them from melting and sliding into the sea.

They accept that “potential risks, especially to local ecosystems, need careful analysis”, but argue that “in our view, however, the greatest risk is doing nothing”.

Proponents argue that geoengineering may be the only way of preventing climatic harms in the absence of substantial emissions reductions – a form of insurance to keep the Earth habitable that would be negligent and unethical to spurn.

Sceptics contend that manipulating our planet’s climate may provoke unforeseen, unintended and uncontrollable consequences.

Intrinsically uncertain

SRM is relatively cheap but technically difficult and riskier than CDR, which is safer but more expensive. CDR is unproven and probably impossible to deploy at scale in time to prevent catastrophic global warming.

SRM is fast but uncertain and could have unintended effects that cannot be unwound. SRM is designed to offset the effects of emissions without reducing them, whereas CDR addresses the cause of climate change.

Since we cannot know how the biosphere will respond to forced interventions, we don’t know whether SRM will increase acid rain and ocean acidification or, paradoxically, reduce global rainfall but increase flooding.

Disruption to the Asian monsoon would threaten the food and water security of nearly two billion people. CDR is risky because bioenergy capture and sequestration could require diverting arable land from food production, consume significant amounts of water and energy, and lead to severe soil degradation and land grabs in the global South.

Because scientists are unsure whether SRM can be safely deployed in large-scale field trials, they rely on modelling that is intrinsically uncertain.

Markets and technology

There is a danger that SRM could lead to technological lock in because sudden withdrawal might result in rapid and unmanageable warming.

We cannot be confident that average global temperature will not spiral if climate engineering is suddenly terminated, meaning perpetual dependence on risky technologies.

In 2014, researchers compared five geoengineering methods and concluded they were relatively ineffective and carried potentially severe side effects. Conventional cost-benefit analyses are ethically problematic when applied to risks that cannot be reflected in monetary terms such as threats to food and water security.

Another risk is that geoengineering creates a moral hazard by fostering false hopes that science will produce a ‘get-out-of-jail-free’ card that obviates the need to cut emissions and benefits free riders willing to gamble with humanity’s future in the expectation that climate change is containable.

They include ecomodernists who believe that markets and technology provide solutions to every environmental problem.

Effective remedy

This delusion reflects a powerful strand of hubristic, Promethean Western thought in which humanity’s separation from and mastery over nature is considered normal rather than the perverse rationality that has brought us to the brink of ecological catastrophe.

Three of nine planetary boundaries — biodiversity loss, climate change, and the nitrogen and phosphorous cycle — have been breached in the Anthropocene and the remainder are under threat.

So how should we respond? Is it ethical or wise to entrust control of the planet’s thermostat to unilateralists like Trump or Putin? Should we permit geoengineering research but place a moratorium on its deployment in the hope emissions reductions will succeed?

If they don’t, how should we respond to pressures that will inevitably increase to engineer the climate? Is it possible to secure agreement through democracy and procedural justice?

Consent might be expected if the benefits of a technology outweigh its risks, if it provides an effective remedy that is containable and reversible, avoids moral hazards, and protects human rights and minimises harms to future generations – who cannot be consulted.

End-of-pipe solutions

The history of climate governance suggests that the consent of the most vulnerable is likely to be restricted, given under duress and ethically unacceptable.

Women, indigenous peoples, social movements and NGOs have historically been excluded from effective participation in climate governance.

Entrusting decisions on geoengineering to a small, expert geoclique would be undemocratic, unaccountable, disturbingly technocentric and thoroughly depoliticising.

Geoengineering may be a lesser evil than climate change but still be so deeply harming that it should be regarded as a ‘marring evil’.

Mike Hulme describes climate change as a wicked problem that science cannot and should not try to fix. He argues that “the dream of a global thermostat in the sky is undesirable, ungovernable and unattainable”, and stratospheric aerosol injection “is the wrong sort of solution to the wrong sort of problem”.

Viable alternative

He added: “Human-induced climate change is not the sort of problem that lends itself to technological end-of-pipe solutions”.

Albert Einstein observed that no problem can be solved at the same level of consciousness that created it, but it is simpler and more ethical to fix our attitudes rather than attempting to fix the climate?

After all, Stephen Gardiner asks “if the problem is social and political, why isn’t the solution social and political as well?” The alternative is the risk of unknowable harm to the conditions of life and survival for humans and other species.

Resisting the siren calls of unproven technologies is prudent rather than Luddite, especially now that renewable energy enables us to decarbonise the global economy by the middle of the century with sufficient political will.

In the absence of a technological silver bullet there is no viable alternative to reducing greenhouse gas emissions and the burden of proof is on those who want to engineer the climate.

This Author

Dr Sam Adelman was speaking at Climate Change: Is It Time for Extreme Measures? at Edinburgh International Science Festival earlier this week. More information and tickets can be found online.