An image in the online Encyclopaedia Britannica illustrating the various strategies for climate engineering has always bothered me. Alongside the highly technical and speculative proposal of placing orbiting mirrors in space to intercept the sun’s rays sits the highly unsophisticated and low-tech proposal of wrapping melting glaciers with huge sheets of white fabric. The juxtaposition is extraordinary. One looks like a technology fit for the twenty-second century. The other looks like it comes straight out of the fourteenth. It is as if someone were explaining to you that two of your best options for communicating with distant family members were tapping numbers into an iPhone X and picking up two tin cans connected by a long piece of string.
Both of these strategies for fighting back against global warming involve what the experts call “solar radiation management.” This Matrix-sounding phrase describes deliberate interventions into the workings of the climate system in order to reflect a small portion of incoming solar energy back into space before it warms up the planet.
Getting the ‘energy-in’ to ‘energy-out’ balance right is the key to keeping the planet cool. It is now established beyond any serious doubt that too many heat-trapping gases emitted into the atmosphere are keeping way too much solar energy from escaping into space. Since those warming gases already released are likely to be sticking around for a while, solar radiation management could be a viable technique for limiting the amount of additional energy allowed in. Some suggest it can serve as a stop-gap measure until something more permanent can be done to reduce atmospheric carbon. The discussion of the potential of these technologies is, shall we say, heating up. (Previous posts on this blog have raised some of the ethical issues here and here).
There are two reasons why the idea of putting orbiting space mirrors and glacier wraps on the same diagram seems strange. The first is the obvious difference in sophistication. The second is the difference in the problem they each attempt to tackle. In the case of wrapping the glacier, engineers would be attempting to save individual glaciers on a case-by-case basis for as long as they can be saved. There are plenty of good reasons to do this based on a glacier’s importance for water supply, agriculture, and local temperatures. In some high-altitude locations in Peru where glaciers have already disappeared, locals are experimenting with coating rocks with white paint to simulate the reflective surface of the ice and snow that has now vanished. The increased whiteness cools the area and preserves water for crops and animals.
Reflecting back incoming sunlight with mirrors attempts to grapple with the problem at a much more systemic level. While this strategy notably fails to do anything about the greenhouse gases that remain at the root of the problem, it would address the overall ‘energy-in’ to ‘energy-out’ balance of the planet at a global level. Space mirrors look at the thermodynamics of the system as a whole rather than at the immediate local needs on any one particular mountainside.
Straddling the middle-ground between glacier-wrapping and space mirrors is marine cloud brightening. The first field trials of this technique are expected within the next year or two. Marine cloud brightening involves spraying a fine mist of salt water from self-piloted ships into the air above the ocean surface in order to help clouds to form (and to brighten the clouds that are already there). In the same way that a white glacier reflects more incoming heat than a brown mountainside, so does a white cloud reflect more incoming heat than a green-blue ocean surface. Given that the oceans cover two-thirds of the earth and serve as an enormous heat sink that influences the climate for centuries, stopping a small portion of the sun’s energy from entering the ocean could be a worthy goal.
Marine cloud brightening could be performed at various scales. If you deployed thousands of spraying vessels over vast reaches of the ocean, it might be possible to reflect sufficient sunlight to make a real difference to global temperatures. On the other hand, if you only wanted to cool a portion of ocean, it might be possible to deploy vessels over a particularly vulnerable spot, such as the Great Barrier Reef, in order to reduce the devastating coral bleaching occurring there today. Though the science is not yet well enough understood, cloud brightening could be flexible enough to be as local or as global as you wanted it to be.
Before getting too optimistic about these get-out-of-climate-jail-free cards, it is worth remembering something important about all of these efforts at solar radiation management. Wrapping glaciers, deploying space mirrors, and brightening marine clouds all come with a serious downside. Reflecting sunlight while doing nothing about carbon dioxide levels ensures that atmospheric carbon will continue to acidify the oceans with devastating effects for the marine ecosystem. We might nicely cool the oceans while watching them slowly turn into a mild acid bath.
Placing this one (minor!) consideration aside, the differences between wrapping a glacier, saving a reef, and intercepting the sun with mirrors point to something ethically important. At first the differences appear to be simply differences in scale. The technologies all exploit the relationship between incoming solar energy and reflectivity to various degrees. The techniques, however, embody dramatically different goals. On one extreme, you have local people investing time and resources into addressing a deepening local crisis. On the other, you have engineers attempting to regulate a global planetary process that has operated independent of our designs since the beginning of time. At some point as you move from the local to the global something philosophically substantial changes.
This is what makes the prospect of global scale solar radiation management so scary. In attempting to engineer the whole of the global climate at one time, humans step into a role that they have never before intentionally assumed. If the skies have traditionally been the domain of the Gods, deliberately engineering a new global climate “verges on blasphemy,” claims UK writer Oliver Morton in The Planet Remade. Such efforts, Morton says, reconfigure “what it is for humans to be humans and what it is for nature to be nature.” I have suggested along similar lines that global scale climate engineering would signal a new “synthetic age” for the planet in which humans attempt to turn more and more of earth’s natural systems into increasingly calibrated machines.
This would not be a task for the faint of heart. And, even if such strategies might be helpful under certain circumstances, be cautious if anyone tells you these efforts are 100% guaranteed to end well.