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We know that a change of more than 1.5 C in global temperatures would be disastrous. To even have a 50% chance of limiting the increase to the 1.5 C, we need to get to net zero emissions by 2035. Or, there’s also a band-aid solution to save, or at least pause the fire in, our rapidly heating house.
On Midsummer’s Day in 1991, the citizens of the Philippines witnessed the second-largest volcanic eruption in the 20thcentury. Mount Pinatubo released ash columns 40 km high into the atmosphere, along with tremendous amounts of hot gas and volcanic matter. In total, the eruption expelled more than 5 km3 of volcanic material (about 1.3 times the volume of Zurich Lake), with temperatures of up to 1,300°C. Furthermore, volcanos like these are known to belch out massive amounts of water vapor and CO2, both known greenhouse gasses, into the atmosphere. And yet, in the aftermath of the eruption global temperatures would drop by about 0.4°C from 1991 to December 1992
The Earth’s Radiation Budget
Just like the cup of coffee that has been sitting on your desk for too long, the Earth is in thermal equilibrium with its surroundings. The sun constantly bombards us with photons, injecting energy into the planet, which is either absorbed or reflected. The Earth, in turn, radiates energy corresponding to its temperature, like a near-perfect black body. These energy fluxes (absorption, radiation, and reflection) keep the Earth at an average equilibrium temperature of 15°C, which is, you could argue, just as God intended. Climate change is simply a perturbation to one of these energy fluxes, which demands a new equilibrium. Unfortunately, if the new equilibrium happens to be even a couple of degrees above the status quo, it could come at a massive human cost.
To understand climate change, we must understand our radiation budget and all the factors at play in the intricate dance that is our climate system. One such factor is albedo, which can be thought of as the earth’s reflectivity. It is measured on a scale from 0 (an ideal black body that absorbs all incident radiation) to 1 (total reflection of incident radiation). On this scale, the Earth falls at about 0.3. Snow has a high albedo, with the Antarctic snow cover averaging an albedo of 0.8. Climate models predict that seemingly small changes in the planet’s albedo could have far-reaching implications for the average surface temperature. According to a researcher at the Lawrence Berkeley National Laboratory in California, changing the Earth’s albedo by painting all the roofs and roads in the world white (about 2.4% of the earth’s surface) would cool the earth enough to offset the warming caused by 44bn tons of CO2. At first, it sounds like an extremely stupid idea, but if it results in the cancellation of more than a year’s worth of anthropogenic CO2emissions, I think it no longer qualifies as one. But what does all this have to do with the volcano in the Philippines?
Sulfur Dioxide and Solar Geoengineering
Returning to the case of Mount Pinatubo, the thermal contribution of the enormous amounts of geothermal energy released was dwarfed by the reduction in solar irradiation caused by the eruption. The volcanic event injected large amountsof ash. And, more importantly, 20 million metric tons of sulfur were introduced into the stratosphere. While the ash is good at blocking the sun’s rays from reaching the Earth, it settles down in a few days, and everything returns to normal. On the other hand, the sulfur oxides and dioxides combine with water in the stratosphere to form tiny droplets of sulfuric acid. These light, reflective droplets hang in the stratosphere for months and even years, increasing the albedo of the earth (just like white paint!) and cooling our planet. That explains the mystery of the drop in global temperatures in the years following the eruption. The question that remains is: Can we use this effect to our advantage? And, if yes, should we, and will we?
The short answers to those questions are yes, probably not and most likely yes. Things are not going our way, as far as the climate is concerned. I am sure that most people reading this article know how badly we are doing regarding mitigating a climate catastrophe. It has been established that anything above a 1.5°C change in average global temperatures will lead to disastrous consequences for most life on the planet as we know it. Yet, as the graph above shows, to even have a 50% chance of limiting the average warming to 1.5°C, we would need to reach net zero emissions by 2035. Considering the current global trend of increasing yearly emissions, humanity has not even reached the summit of this mountain, let alone begun its descent towards a better future.
This is why, in 2023, both the US and EU commissioned research into solar geoengineering, and scientists worldwide have begun to discuss the topic seriously. In the past, solar geoengineering has always been treated like a dangerously radical idea. Artificially dimming the sun without knowing the consequences on global climate patterns is playing with fire: one wrong move, and one’s house burns down. But when the metaphorical house is about to catch fire anyway, perhaps every solution, even one as risky as managing solar radiation, starts to seem reasonable. So, how do we do it? If we, like a very efficient volcano, could inject just 1.2 million tons of sulfur into the correct parts of the stratosphere, we could cool the planet by about 1°C. The advantage of this plan is that it is incredibly cheap, costing only about 20bn USD per year. This also makes it accessible to any billionaire with sufficient funds, or the head of state of even a small country. It only seems like the logical choice to use this solution to pause global warming to 1.3°C until we are able to slash our emissions completely.
This is where we come to the house-burning-down effects of this technology. First, we do not have enough research to predict the effects on our complex climate system fully. It could disrupt weather patterns and cause extreme climate events if done incorrectly. Second, it would increase the incidence of acid rain and likely harm the ozone layer. Lastly, and probably the most likely, is the problematic effect the approach would have on human complacency. Solar geoengineering is far from being a sustainable long-term solution to anthropogenic climate change; it is a poorly fashioned band-aid that will stop the bleeding for now, while we regain our strength. And we should treat it as such. Once it is implemented, we will be on borrowed time. And if we do not honor our side of the climate bargain by reducing our emissions to zero, our brokered peace will not last long.
If successfully implemented, solar geoengineering will surely be a landmark event for mankind. And dimming the star that we depend on for our existence in order to accommodate our needs does indeed feed into humanity’s God Complex. I hope that we can play out our science-fiction fantasies in the best possible way, by implementing technologies only when they are backed by sufficient research and only to save our species from an extinction event.
