Can Solar Radiation Management Stop Climate Change? 太阳辐射管理能不能解决咱们的气候变化问题？

I recently attended an international workshop in Beijing that brought together scientists, academics and others from a diversity of professional backgrounds and different countries in order to discuss how to internationally govern research into solar radiation management (SRM). SRM is a type of geoengineering which consists of engineering our atmosphere to reflect more of the Sun’s radiation away from earth, effectively dimming the earth slightly, in order to cool the earth and reverse climate change. Two main ways of achieving this were presented at the workshop; spraying sulphur dioxide (SO₂) 30-40km up into the stratosphere where it would disperse around the earth and reflect sunlight back into space, or spraying seawater into clouds to make them more reflective. According to scientific models of the climate, we would need to reflect around 2% of sunlight away from the earth in order to reverse climate change, even if we meet the CO₂ emissions targets we set at the Paris climate change conference in 2015. Sounds great, until you look at some of the unknowns involved…

To me, it appeared to be the case in the workshop that spraying SO₂ into the stratosphere may be preferred to whitening the clouds because the SO₂ would stay up there for years, rather than being rained down every few days like the seawater in the clouds would be. It is believed that the SO₂ would reflect enough sunlight to reverse the changes in rainfall patterns that we are beginning to see due to climate change, although rainfall patterns would still not be as they were in the past, just less different than they could be under runaway climate change. However, the models used to predict this are limited in their accuracy, in reality rainfall and temperature patterns could change in ways we don’t expect if we deliberately interfere with our climate. Moreover, we don’t know anything about the effect that SRM would have on the ozone layer, or whether there could be any negative impacts on our health as the SO₂ particles slowly trickle down to earth. It could also cause an increase in acid rain and affect the health of many species of plants as the light reaching them would be more dispersed. The trickle down effects these unknowns could have on ecosystems, and ultimately us, are also unknown.  More research is needed to find answers to these questions; it could be possible to answer some of them through harmless small-scale experiments such as putting a kilogram of SO₂ into the stratosphere and observing its effect on the ozone in a localised area. However, in order to be completely sure about the effect SRM would have on our climate there is no way to test it other than a full-scale global experiment, because you cannot isolate a small ‘piece of climate’ to work on. If such an experiment were to take place we would have effectively already implemented SRM.

There are also unknowns in how people would react to SRM. SRM scientists do not believe that this technology should replace efforts to reduce our dependence on fossil fuels, but not everyone would see it the same way. Could fossil fuel companies, some governments and others use it as an excuse not to reduce CO₂ emissions? Could it be an excuse to continue rapid deforestation? Some studies show that people drive faster with a seatbelt on because they feel safer; we might replicate this effect if we felt we were safe from climate change. If this happened, then we could never stop using SRM, as our atmosphere would be filling up with more and more greenhouse gases, meaning that if we stopped using it we would suddenly experience very extreme, violent climate change that we would not have any time to adapt to. What’s more, the political implications of deliberately engineering the earth’s climate are huge. If SRM is implemented by one or two countries who are suffering badly under climate change, and other countries believe that their climate has been made worse as a result, could it lead to war? One purpose of this workshop was to expand international dialogue around SRM research and make it more inclusive to try to avoid such a scenario, but politics can be almost as complex and unpredictable as our climate, so coordinating such an important global project would be extremely complicated.

So where is the relevance of all this to China? Until now SRM research has been conducted almost entirely by European and American scientists, one purpose of this workshop was to bring China and other nations firmly into the discussion. If China were to be left out, the Chinese government would have a legitimate reason to reject all research into SRM since it would have no control over it. China is already suffering from water scarcity and drought in the north and flooding in the south due to climate change, which has historically mostly been caused by European and American greenhouse gas emissions; the last thing they would want is for Western governments to deliberately interfere with their climate without having a say in the matter. Moreover, China is seen by some as a country which already has some expertise in large-scale geoengineering projects; they are already engaged in a huge project to divert water from the rainy south to the dry north, they have planted hundreds of millions of trees to capture CO_2, reduce drought and block sandstorms, and they are engaged in smaller scale weather manipulation. If China turned its scientific attention toward SRM it could provide a valuable contribution.

In the end though, opinion in the room was split over whether we should really be pursuing SRM research. Even SRM scientists recognise that they don’t want to implement it, as the risks are huge, but they believe we need it as a backup plan because it does seem to be the case that we are probably heading for runaway climate change at some point, the effects of which would be catastrophic. Some people believed we should still be putting most of our scientific effort into reducing greenhouse gas emissions more, some believed we should be focusing more on how to adapt to climate change as it seems to be too late already, and some believed now is the time to be researching SRM because even if we learn to adapt, we won’t be able to adapt to all of the changes coming our way.

My own personal opinion is that we need to simultaneously focus our energy on reducing greenhouse gas emissions and learning how to adapt to climate change. SRM has only received $25 million of research funding globally so far; personally I believe this may be an appropriate amount. The thought depresses me of living in a science fiction-like world where environmental destruction has become so out of control that a few governments, or even worse a few corporations, are spraying chemicals into the stratosphere to dim the sky and attempt, quite possibly in vain, to manipulate our climate. Although I do understand that we may reach a time when it becomes sadly necessary to implement SRM I still think there is a lot more we could do now to put that day off for as long as possible, or hopefully forever. Many cultures in the human race have long believed they are capable of manipulating nature without unexpected side effects, and they have often been wrong. For example, 150 years ago nobody had any idea that burning coal to make ships and vehicles go faster than the wind would blow them or horses would pull them would cause climate change and all the environmental changes it entails, when we wiped out wolves and beavers from the UK we didn’t expect it could cause flooding problems for future generations, when we decided to give antibiotics to all our livestock we didn’t expect diseases to get stronger and stronger until we don’t have antibiotics strong enough to deal with any further mutations… Although those trying to develop SRM are doing it in good faith, trying to provide us with a get out of jail free card in case we fail to curb our greenhouse gas emissions, I fear that it could be our next big mistake. But then, climate change is happening whether we like it or not, so how will we ever be sure about the effectiveness of SRM as a possible solution if we don’t conduct the research to find out…? Any opinions are very welcome, as we need an international dialogue on this important technology that may affect our planet and those living on it for hundreds, or thousands of years.