The 2015 Paris Climate Agreement set what now appears to be a very bold target – to hold the rise in global average temperature to well below two degrees Celsius and to try and limit the temperature increase even further to 1.5˚C. That was the goal; it now seems almost certain that it won’t be reached. To halt warming to a 1.5˚C rise, carbon emissions would need to drop off a cliff. Far from being close to the required plunge, global emissions are still increasing. ‘To be blunt, it’s impossible to meet the one and a half degree limit unless we are deeply fortunate about some unknown feedbacks, or the climate sensitivity parameter is a lot lower than we expected,’ says John Moore, chief scientist at Beijing Normal University and professor of climate change at the University of Lapland. ‘The rates of decarbonisation that are required are unprecedented, and we’re not talking about five per cent. No, we’re talking about 15 per cent, maybe 20 per cent per year. That’s crazy. Undoable.’
The world, it seems, is going to warm and the consequences are both far-reaching and well-documented. Cutting emissions is largely understood as the solution, and it’s not happening. Could there be another way?
In 2009, the Royal Society, the UK’s independent scientific academy, published the findings of a major study called Geoengineering the climate: science, governance and uncertainty. In the paper, ‘geoengineering’ was defined as the ‘deliberate large-scale manipulation of the planetary environment to counteract anthropogenic climate change’.
The paper split geoengineering into two categories: Carbon Dioxide Removal (CDR) techniques, which remove CO2 from the atmosphere; and Solar Radiation Management (SRM) techniques, which ignore carbon altogether, and instead reflect a small percentage of the sun’s light and heat back into space, thereby cooling the Earth’s surface. ‘These methods act quickly, and so may represent the only way to lower global temperatures quickly in the event of a climate crisis,’ stated the report. Put that way, SRM sounds like an ideal solution, though read on and the paper adds that such methods ‘...only reduce some, but not all, effects of climate change, while possibly creating other problems. They also do not affect CO2 levels and therefore fail to address the wider effects of rising CO2, including ocean acidification.’
More than ten years later, geoengineering the climate is still a science in its infancy. Though embraced by the IPCC and by many policy-makers, CDR technologies are widely acknowledged to be way behind where they would need to be to have any real impact on global warming in the short term. So far, only two dozen carbon capture projects are operating around the world, and the results from them are debatable.
As for SRM, it remains more science fiction than science reality. No true tests of SRM methods have been carried out, the technology to execute it does not yet exist, and no government has engaged in any significant way with the prospect. But that doesn’t mean things won’t change. While they are a small cohort, there are serious scientists all around the world grappling with SRM, trying to figure out if a) if it would work and b) if it could ever be deployed safely and ethically. Their goal is to ensure that, as we fail to hit warming targets and as the impact of that failure becomes more obvious, we understand the impact of SRM, just in case it is finally deemed necessary.
What’s more, interest in SRM is very gradually creeping into wider policy discussions. In October last year, scientists met in Berlin to discuss the future of geoengineering. Last November, the US House of Representatives held a subcommittee meeting on geoengineering, with SRM dominating the conversation.
ENGINEERING THE CLIMATE
SRM encompasses a range of different interventions but the two most well-researched are stratospheric aerosol injection and marine cloud brightening. The former would involve spraying aerosols high up into the stratosphere. The technique could cool the planet in a similar way to a large volcanic eruption. When a volcano erupts, it sends an ash cloud high into the atmosphere. The sulphur dioxide released in the plume combines with water to form sulphuric acid aerosols, which are able to reflect incoming sunlight.
Marine cloud brightening would involve deploying ships to spray saltwater into the clouds above the ocean.
Once airborne, the salt particles would facilitate the condensation of water vapour into liquid. As more water droplets are created, clouds would appear larger and brighter. These brighter clouds would reflect away more sunlight and cool the atmosphere.
The difficulty of researching these approaches lies in the fact that you can’t just give geoengineering a go. By definition it involves altering the global climate. The potential consequences are so huge and far-reaching that to test it would be pure Dr Strangelove madness. Instead, scientists largely rely on climate modelling to work out if SRM could work.
‘You use the same computer models that you use for simulating climate impacts. And you try to model what would happen to a future climate if you decrease the amount of sunlight that reaches the planet,’ explains Dr Andrew Parker, a senior research fellow at Bristol University who has worked on SRM for more than a decade. ‘Or it might be more sophisticated, you might actually model what happens when aerosols go into the stratosphere at diff erent altitudes and latitudes. And then you see what the earth system does. Of course, these models don’t produce facts. They are not accurate predictions of what’s going to happen. But they’re not useless. They give you an idea based on the best of our knowledge, how the earth system would respond to certain changes.’
Not all modelling to date is conclusive, but it is fair to say that climate models have shown that solar geoengineering, when used in moderation and combined with emissions cuts, has the potential to reduce global temperature. In a 2019 research paper, Jesse Reynolds, an Emmett/Frankel fellow in environmental law and policy at UCLA School of Law and author of the book Governance of Solar Geoengineering wrote that ‘current evidence indicates that some suggested solar geoengineering techniques could reduce climate change and its associated risks effectively, globally, rapidly, reversibly and inexpensively. They also seem to be technologically feasible.’
Nevertheless, all researchers in the field remain extremely cautious. ‘We’re trying to build slightly more advanced future scenarios, to try and understand a bit more deeply what would happen, but research is still fairly young,’ says Helene Muri, an SRM researcher at the Norwegian University of Science and Technology. ‘It’s far too early to say whether it’s a good idea to do it or not.’
The main reason for this caution is that any type of SRM could have big side-effects (those ‘other problems’ mentioned in the 2009 paper) which impact other aspects of the climate. Research has suggested that SRM could lead to changes in water availability and rainfall patterns and that these impacts would vary across different parts of the globe.
‘There are very large uncertainties here,’ adds Muri. ‘Maybe we think we understand the very large scale response of the climate from what we’ve been studying in the models so far, but how this might play out in the real world and affect regional climate and weather is very uncertain.’
In a 2020 study titled: Reflecting sunlight to cool the planet will cause other global changes, researchers at MIT found that, in an idealised scenario in which solar radiation was reflected enough to off set the warming that would occur if carbon dioxide were to quadruple, SRM would weaken extratropical storm tracks in both hemispheres. Weakened storm tracks would mean less powerful winter storms (potentially a good thing), but the researchers also warned that weaker storm tracks can lead to stagnant conditions in summer and less wind to clear away air pollution. Changes in winds could also affect the circulation of ocean waters and, in turn, the stability of ice sheets.
GOVERNING THE GLOBE
It is these unknowns that make SRM so controversial – there are some who vehemently believe it is foolish even to carry out research. How could you ever govern a technique that could affect different parts of the globe differently? Who would have the right to implement decisions?
‘If anyone does it at scale, they will be influencing the climate for everyone else on the planet in every other country,’ says Parker. ‘That’s what makes this so difficult. In theory, one decision maker could make this decision for everyone else.’
It is for this reason that some researchers in the field specialise in questions of governance and ethics, regarding both deployment of SRM and research into it. Though their work is only speculative, prevailing attitudes mean it’s not always an easy field to work in.
‘I very much have the experience, and I think a lot of researchers in the field have similar, that there is almost a quasi-religious objection to doing geoengineering,’ says John Moore from Beijing Normal. For some, SRM simply smacks too much of playing God. Others point to the risk that the existence of tools to cool the atmosphere could dent interest in climate mitigation, and lengthen reliance on fossil fuels.
But for Parker, to not even research the topic would be a mistake. ‘The field has this false spectrum between people who are modest enough to say that they don’t know and they need more evidence, and people who are ideologically against solar geoengineering, and for whom it would be easy and convenient if they could dismiss people like me, people like my colleagues, as the puppets of oil companies, or as climate deniers.’
In fact, argue researchers, the field is made up almost entirely of environmentalists, studying SRM as a last resort. If it turns out to be a bad idea, so be it.
‘There are no true solar geoengineering advocates. They overwhelmingly consist of reluctant advocates of research, exploring the ideas because they have been disappointed with the response of reducing greenhouse gas emissions,’ says Jesse Reynolds. ‘I think what motivates a lot of people, including myself to work here, is a recognition that one: climate change poses severe risks to humans and ecosystems, especially those that are already the most at risk. Two: we’re not going to be able to prevent severe climate impacts through other means, such as reducing greenhouse gas emissions. And three: the evidence continues to mount that solar geoengineering could reduce climate change, and its impact.’
In his recent paper on the subject, Reynolds summed up a number of possible governance mechanisms for SRM, covering topics such as intellectual property and compensation for those harmed by activities. So far, he concludes that it’s too early to say what the best decision-making forum would be, but he notes that most people think the more countries involved the better, though a veto power for any one would make the system unworkable. He adds that fears that a single country, or one maverick individual, could use SRM against the expressed wishes of the international community, while understandable, are exaggerated. ‘We have various mechanisms in the international community, of issue linkage, and persuasion and compromise, where such outlying behaviours tend to not happen.’
Nevertheless, that’s not to say one voice couldn’t cause trouble. ‘The real risk in the solar geoengineering conversation is that political actors who have traditionally resisted action on climate change are going to grab it and run with it,’ Reynolds adds. ‘That President Trump is going to say: Well, now we have the solution. Until now, fortunately, that hasn’t happened, because that would really poison the discourse.’
SECURING A SEAT AT THE TABLE
There is another side to ethically researching SRM. What research there is, as in so many fields, is dominated by rich, Western countries, yet the most hard-hit by temperature rise are likely to be those in developing countries. Andy Parker thinks that scientists in these countries need to have a seat at the table in any future discussions on the subject. To this end he set up The Solar Radiation Management Governance Initiative (SRMGI) to expand the conversation and the connected Decimals Fund, an SRM research fund aimed at scientists from the Global South. The fund supports eight teams of scientists as they model how SRM could affect their regions. Heri Kuswanto, director of graduate programmes and academic development at the Institut Teknologi Sepuluh Nopember (ITS) in Indonesia is one such scientist. ‘My project investigates the impact of SRM on extreme temperature and precipitation change in Indonesia,’ he explains. ‘Climate change is a big issue in the world and in Indonesia as well. We definitely need to be involved in SRM research because we are from developing countries that will be impacted by this intervention. We are scientists and what we do is find out the scientific evidence on what the SRM impact would be. We are not in the position of supporting or against SRM. We will share our finding, whatever it is.’
So far, Kuswanto’s research indicates that SRM could be effective in reducing warming, as well as having other climatic effects. ‘I cannot say a lot about rainfall because we are still working on it. However, we have the initial results analysing the rainfall over Java island. It is interesting to see that SRM would be able to reduce extreme precipitation.’
Izidine Pinto, a researcher in the Climate Systems Analysis Group at the University of Cape Town is another Decimals Fund recipient. His work focuses on the impact of SRM on regional characteristics of drought and heat extremes in Africa. Modelling done so far indicates that SRM could reduce warming caused by increases of greenhouse gases and would reduce temperature extremes during the 2051-2080 period of study. ‘However,’ he adds, ‘SRM can’t solve both changes in temperature and rainfall. In some parts of Africa SRM is not effective for rainfall. Some areas get better and others get worse.’
What’s key, according to John Moore, is that developing countries have a very different attitude to SRM. ‘I think it’s really important to stress the difference in attitude between the developing world and the developed world when it comes to doing geoengineering,’ he says. ‘The less you’ve got to lose, which is essentially everybody in the developing world, the more willing you are to look at the possibilities. We get a very, very biased view. Geoengineering is certainly something that is looked at much, much more positively in the developing world.’
It’s a sentiment that Kuswanto appears to echo. ‘People here would easily accept the SRM idea if we can show some positive impacts that have been validated scientifically,’ he says – an ‘easy acceptance’ that contrasts starkly with the alarm more commonly espoused in the West.
It may be that humans never carry out SRM, that the effects are deemed too risky, the governance too difficult. But what’s clear is that one way or another, humans will have to adapt to a warming world. We have failed to lower emissions and as a result, even if it’s not SRM, huge, expensive interventions will be needed; whole cities will need to be moved, whole mangrove groves and coral reefs created, giant walls built. Very soon, we will be past the point of gradual mitigation and perhaps then, geoengineering research will be discussed with a louder voice.
If that day comes, those who study this controversial science won’t be jumping for joy. Their best hope is that the work they do will provide a solid backbone to any real-life projects, one that ensures action is fair and safe. There are few other fields in which researchers would gladly see their work deemed futile, but SRM is one. ‘Everybody would like it if there was a nail in the coffin,’ says Moore. ‘We could stop wasting our time and look at adaptation and deal with it as gracefully as we can. But if there’s an alternative... well, we have a duty to try to look at it.’