Despite some recent articles by some major news outlets there is no plan to dim the sun in order to combat climate change. Thankfully that suggestion is still well out of reach of science, of course perhaps we should try raking the surface :). The article that these outlets were referring to is by Smith and Wagner (2018). What they are actually looking at is the feasibility and costs of injecting sulfates into the stratosphere (one layer of the atmosphere, it is where the ozone layer sits). But why would you want to do this?
Different chemicals respond to sunlight differently. Some chemicals will reflect sunlight back, while others let the light through. Sulfates are the best studied of these reflective chemicals that we might inject into the atmosphere which is why Smith and Wagner opted to use these chemicals in their analysis: a little more is known about the potential effects, intensity of effects, and potential side effects. Notice I said a little more, this is by no means a fully predictable excursion. The idea of injecting the sulfates is to reflect some of the sunlight before it gets to earth. This would in theory help to mitigate climate change. It does not solve climate change and the authors do not suggest anything of the sort. Basically it would give us a little more time to actually make the cultural changes necessary to stop sending excess greenhouse gases into the atmosphere. And yes I meant cultural changes because while things like renewable energies and energy efficiency are both great things that we need to pursue we need to change the way we think about and interact with the world before we will really be taking action to prevent climate change.
So why do we want sulfates in the atmosphere but not greenhouse gases like carbon dioxide? Well, while the sulfates reflect sunlight before it reaches the earth, greenhouse gases trap energy by letting the sunlight through and then reflecting the longer wavelength infrared light that reflects from the earth back to the earth. It’s kind of like going through security at the airport, we can get from one side to the other but we can’t go back through if we want to leave again. We need some greenhouse gases in the atmosphere, they’re what keeps earth at a relatively stable temperature, but when we started burning fossil fuels, cutting down forests, mismanaging our soil, and raising animals (lots of animals) for food we increased the amount of greenhouse gases that are emitted and reduced the amount that are stored. It’s kind of like if you get a new job that makes more money so you get excited and start spending more, but then you also start dipping into your savings to spend even more. Now you aren’t storing money, you’re spending what you had stored, and you’re probably filling your house with things you don’t actually need.
I think this statement from the original article sums up the goal of the research itself “We here make no judgment about the desirability of SAI. We simply show that a hypothetical deployment program commencing 15 years hence, while both highly uncertain and ambitious, would indeed be technically possible from an engineering perspective. It would also be remarkably inexpensive” (section 5, para 1). The problem is that many science communicators, if you can call them that, don’t actually look at the science, they look for the headline. Dimming the sun to combat climate change will, at least in theory, encourage people to click on your story, but it doesn’t help anyone to understand what is actually being examined. And we really need to stop reacting in this way.
Did you know that HFCs, which are the compound used in many cases to replace CFCs (remember the chemicals that resulted in a hole in the ozone) are one of the most potent greenhouse gases and have a life in the atmosphere of thousands of years? I know the authors of this article are not saying lets definitely do this, lets inject another chemical with potential unknown consequences into the atmosphere, but that ends up being what it looks like by the time it gets interpreted through the lenses of some journalists and then everyday citizens. Which brings me to a different question in the end, we’ve often asked if scientists are responsible for the ways their discoveries are used (case and point: the atomic bomb), but perhaps we should also ask, are scientists also responsible for looking at how their discoveries or research is understood and interpreted? It seems that Wagner at least seems to think that they have some responsibility on that front as well.