In an open letter, dozens of scientists speak out against a regularly suggested solution to our climate problem: solar climate engineering.

The earth is warming rapidly. Attempts to reach effective international agreements to curb greenhouse gas emissions and thus also global warming are proving difficult. And every now and then there are also voices to change tack and focus not (just) on the cause of the climate problem (our emissions), but instead its symptoms (a higher temperature). to fight. And a method that is often cited is solar climate engineering. In an attempt to lower global temperatures, sunlight would be blocked or filtered on a large scale. You can (in theory) do this in different ways (see box below). But the method that is most often cited is stratospheric aerosol injection (SAI for short). This approach is loosely based on the catastrophic volcanic eruption that occurred in the Philippines in 1991. In that year, the volcano Mount Pinatubo released large amounts of sulfur into the lower layers of the atmosphere (the troposphere and stratosphere) and those sulfur particles blocked the sunlight for some time and thus single-handedly caused the global temperature to drop slightly. The idea behind SAI is that we can achieve a similar effect by releasing particles (aerosols) into the atmosphere on a large scale. Those particles would then reflect part of the sunlight and thus reduce the (global) temperature.

no go

On paper, stratospheric aerosol injection may seem like a good idea. But in a open letter dozens of scientists this week are very clear: solar climate engineering in general and stratospheric aerosol injection in particular is a no-go.

In addition to the injection of aerosols, there are other methods of filtering or blocking sunlight. For example, it should also be possible to make clouds brighter and therefore more reflective and thus block more sunlight from the earth’s surface. This method could mainly depress the temperature regionally. Another approach focuses on thinning cirrus clouds. Cirrus clouds also reflect sunlight and thus have a cooling effect. But unlike other clouds, they absorb infrared light at the same time, which gives a warming effect. The cooling and warming effects of cirrus clouds naturally cancel each other out. But if we managed to make these cirrus clouds thinner, they would absorb less heat and thus the cooling effect would be greater. And so the cirrus clouds could then contribute to lower temperatures. Another frequently cited approach, but not taken seriously by scientists, is to place large mirrors in the room that reflect sunlight.
The fact that stratospheric aerosol injection can count on the most attention among all these possible methods is mainly due to the fact that this approach could lead to a worldwide cooling, seems technologically feasible and affordable.

Risks

There are several reasons why dozens of scientists are turning against solar climate engineering in general and stratospheric aerosol injection in particular, the open letter states. For example, the researchers – including a few Dutch people – first point out that we are not yet fully aware of the risks associated with solar climate engineering. “Its impacts will vary from area to area and there is uncertainty about the effects it will have on weather patterns, agriculture and food and water supplies,” the researchers said. More research may remove some of that uncertainty, but it seems likely that there will always be question marks.

Symptom relief

In addition, the researchers emphasize that solar climate engineering is symptomatic. And they fear that just the idea that we can save the climate in this way could stop governments and companies from tackling the root cause of the climate problem.

Regulate

But what worries the researchers most is the fact that there is currently no international institution capable of effectively regulating the global deployment of solar climate engineering techniques. The scientists point out that for the use of, for example, stratospheric aerosol injection at an international level, agreements must be made about where and how this will take place and for how long, to what extent aerosols will be injected and who is responsible for any (unforeseen) effects of this approach. And because all countries are affected by the deployment of solar climate engineering, all countries must also have a say in the matter. The right of veto for rich, powerful countries – as you often see in international institutions – is not an issue here. Not in the last place, because it is especially important for the poor, powerless countries to have heard about this. Simply because their populations – which often already suffer from hunger and live far below the poverty line – also have the most to lose if the use of solar climate engineering were to have an (unforeseen) negative effect on their environment. In short, deploying solar climate engineering on a global scale requires a whole new, democratic international organization with unparalleled enforcement powers,” the researchers said. “There are no such organizations.”

Ban

And its formation seems far away. And in the absence of such an organization there is a danger that a few rich countries will soon use these techniques on their own or in cooperation with each other and against the wishes of most countries. And that must be avoided at all costs. “That is why we call on governments, the United Nations and other parties to take immediate action to prevent the normalization of solar climate engineering as a solution to the climate problem.” If it is up to the scientists, there will be an international agreement that these methods will not be used. Funding for the development of technologies to enable solar climate engineering should also be banned. Just like patenting that technology and experimenting with it in the open air.

And some haste is needed, because interest in solar climate engineering is increasing rapidly in several industrialized countries. For example, several scientists have identified the IPCC (International Panel on Climate Change, part of the UN) was recently called upon to look into it. And a committee of the American National Academy of Sciences stated last year that the US – preferably in collaboration with other countries – should also conduct research into the feasibility of solar climate engineering. And to the Harvard University In fact, in an effort to get a better handle on solar climate engineering, targeted research into the behavior of stratospheric aerosols is already underway (although a planned field test in Sweden was recently postponed due to strong opposition from indigenous groups and environmentalists). According to the researchers, it shows that solar climate engineering is increasingly seen as a legitimate research topic and a possible step in future climate policy, at least in certain circles. And that’s worrying. And undesirable. “A carbon-free economy is achievable if we take the right steps. Solar climate engineering is not necessary. Nor is it desirable, ethically or politically manageable in the current context.”