Source Body Text

A series in the Guardian recently declared “it’s time to talk about geoengineering.” So let’s talk about it. And let us start with some simple truths about this cluster of techno-optimistic “quick fixes” which purport to somehow offset our slow progress towards zeroing out planet-warming carbon emissions. Solar geoengineering proposals – reducing sunlight – have received the most attention, but a host of desperate schemes have been proposed in an effort to “fix” the disruption of climate caused by the growing burden of carbon dioxide human activities add to the atmosphere. Many threaten the most sensitive aspects of polar environments, extending even to wildly expensive proposals to dam the Bering strait. If implemented, geoengineering schemes would put Earth’s physical climate in a dangerously precarious state, and introduce a major new destabilizing technology to an already turbulent political climate. The essential thing to understand is that carbon dioxide, once emitted, is only very slowly removed from the atmosphere. A sizable share of it will still be keeping Earth dangerously hot millennia from now. Solar geoengineering proposals involve injection of substances whose effect, by contrast, decays in a matter of years. Some might think this is an advantage of solar geoengineering. We can turn it on and off quickly when the damage it is doing to our planet becomes clear, right? Wrong. Recent analyses demonstrate that it would take as long as two decades to create the required infrastructure. By then we would completely reliant on maintaining it – a tall task in a dangerous world with global conflict. It would only temporarily mask the pent-up warming implicit in the ongoing buildup of carbon dioxide, and this pent-up warming would be released in a catastrophically rapid “termination shock” if circumstances force the cessation of solar geoengineering. So solar geoengineering does not “buy time” for decarbonisation. The same can be said for other geoengineering schemes, which also require sustained maintenance over centuries to millennia. Five hundred years from now, the fabled Bering dam may crumble, but the carbon dioxide wreaking havoc on the climate system will still be there waiting. A lot of unforeseen things can happen in a few decades let alone over centuries. Do we really want to play dice with the planet? Do we want to commit today’s and future generations to maintain these approaches without fail? Collectively, the four of us have studied the physics of climate for the equivalent of well over 100 years; we know how complex it is and how many surprises it holds in store. Since 1990, over its six assessment reports, the IPCC has worked with tens of thousands of scientists, from physicists to economists, to ensure that due diligence is done on the science and potential impacts of increasing carbon dioxide concentrations. It took more than a century of carbon emissions before we could detect that our climate is changing and even longer to attribute those changes, unequivocally, to anthropogenic carbon emissions. It was only in 2015 in Paris that most countries accepted that the world is warming and that we are to blame (and 2023 for UNFCCC to mention fossil fuels in a COP outcome). Now, proponents of geoengineering are proposing to bash the climate with a whole new hammer, and one that engages some of the most poorly understood aspects of the climate system, including aerosols, clouds and regional rainfall patterns. We know that this would trigger much more uncertainty on outcomes, in particular in the case of poorly planned, unmanaged, uncoordinated injections of various substances in the high atmosphere, with no governance framework. Surely, we should insist on the same level of scientific diligence as has been devoted to understanding the regional consequences of greenhouse gas emissions. Climate model simulations can provide an indication of what might go wrong but can provide no reassurance of what will go right. So far there has been no rigorous modelling assessment to explore different solar geoengineering scenarios and no formal intercomparison of the sensitivity of the climate to such interventions, let alone the impacts on regional weather and climate variability. What we do know is that the few models that have been used so far do not even agree on what level of intervention might be required, nor what the response will be. After only 10 years, for the same stratospheric aerosol injection, global cooling can be anything from less than 10C to as much as 30C – a change more rapid than anything we have seen so far from carbon dioxide emissions. We are essentially flying blind. The notion that small-scale “safe” experiments can answer any of the important questions about the magnitude and effects of a deployment is fundamentally naive. Any meteorologist or oceanographer knows that the massive forces involved in the global climate system – such as the great heat redistributing currents of the ocean and atmosphere, or year-to-year fluctuations in cloud patterns – will swamp the effects of any experiment and provide no indication of the efficacy and the risks of deploying solar geoengineering. If we are to seriously consider geoengineering, then we need to make sure that the scientific foundations are in place. But for the most part, this is not the kind of research we are getting in the new tsunami of funding. What we are getting instead is funding targeted at developing the engineering technology for deployment, regardless of the consequences of what that deployment may be. The solar geoengineering techno juggernaut rolls on, with what seems to be a complete disregard for what the damage might be to the planet, and despite several important assessments from leading scientific academies (to which we belong), eg the UK Royal Society, US National Academy, French Academy of Sciences. Each has highlighted the major uncertainties, core ethics and governance issues, urging great caution. This is particularly true of the £60m geoengineering programme funded by the UK’s Aria agency. Aria’s chief aim is technology development, and indeed many of the geoengineering projects they are funding are being done in collaboration with for-profit companies. Even more ominous is the explicit entry of venture-capital funded for-profit startups seeking to make money from solar geoengineering deployment in the near future. The Israeli-US startup Stardust has received more than $60m in venture capital, and their business model assumes near-term deployment. And then there’s Reflect Orbital which wants to put giant mirrors in low Earth orbit; they are pitching sales of illumination rather than solar geoengineering, but the technology is identical and we doubt it will be long before they try to get in on the “cooling credits” game. All of this is happening in the total absence of governance. There are pious calls for governance from some of the pro-geoengineering researchers, but what is the path to get there? Is it governable at all? It is the height of folly to invest in developing the technology – even if we knew what might work – that only serves to enable unrestricted, profit-motivated deployment by outfits such as Stardust. As private companies whose technology is subject to little regulation, they and their backers have no legal obligations to submit themselves to public scrutiny nor to provide any assurances on ensuing climate impacts. Will these technologies be carried out devoid of any serious scientific understanding of the consequences and of social, legal and political concerns? All of this is a huge diversion of resources and deflection from the task at hand. As one of us likes to say, when you’re in a climate hole, stop digging … and burning fossil fuels. It really is, at some level, that simple. Raymond Pierrehumbert is Professor of Planetary Science at the University of Oxford, and was a lead author on the IPCC Third Assessment Report, and the US National Academy’s first assessment report on solar geoengineering. He is a Fellow of the Royal Society Julia Slingo was formerly Chief Scientist of the UK Met Office, and was awarded the Rossby Medal of the American Meteorological Society among other prestigious awards. She has received nine Honorary Doctorates including from Cambridge University. She is a Fellow of the Royal Society and is Dame Commander of the Order of the British Empire, and was a reviewer on the recent Royal Society report on solar geoengineering. Michael E Mann is the Presidential Distinguished Professor in Earth and Environmental Science at the University of Pennsylvania, and Director of the Center for Science, Sustainability and the Media there; he is a Member of the US National Academy of Sciences and Foreign Member of the Royal Society Valerie Masson-Delmotte is Directeur de Recherche at the Climate and Environmental Sciences Laboratory; she has been co-chair of IPCC Working Group 1 during AR6, and co-author of the French Académie des Sciences geoengineering report and a co-author of a peer-review assessment of polar geoengineering options.