If you tuned in recently for “What You Always Wanted to Know About Geoengineering but Were Afraid to Ask, Part I,” you might recall that the post ended with a discussion of a plan to cool the Earth by putting a Saturn-like ring around the equator. Well, if that plan for dealing with global warming leaves you cold, what would you think about using cannons, balloons, and aircraft to inject molecules of sulfur dioxide directly into the stratosphere? No good? Well, would you change your mind if you knew that the sulfur dioxide would prevent some of the Sun’s rays from reaching the Earth by reflecting them back into space?
(Please note: In the upcoming paragraphs, I will try to discuss this idea with my sarcasm-filter in place because, when it comes to upper-atmospheric SRM schemes, this is the one that is currently receiving the most serious consideration.)
Stratospheric Aerosol Albedo Modification
The global cooling that followed a massive volcanic eruption on Mount Pinatubo provided the inspiration for this plan. When the mountain erupted in 1991, it pumped enough sulfate aerosol into the stratosphere to lower average temperatures in the Northern Hemisphere by a few degrees for a couple of years.[i] So some scientists, most notably “father of the hydrogen bomb” Edward Teller, decided that purposefully injecting sulfur into the stratosphere to counter the warming brought on by greenhouse gases would be a jim-dandy thing to do.[ii]
Here’s a passage from a 2002 article he coauthored with Roderick Hyde and Lowell Wood:
[T]he present concern about global warming centers on the inputting of about 7 billion tonnes of carbon into the atmosphere each year and several times this level several decades hence; the annual deployment of barely 0.01% this mass of sulfur—roughly one ten-thousandths as much sulfur as carbon—in appropriate form and location can be made to entirely offset the ‘greenhouse effect’ of the ten-thousand fold greater mass of added CO2.[iii]
So you see, it’s all very simple. It’s like putting on a coat when it’s cold outside or deodorant to mask the olfactory embarrassment of underarm stench. It’s the kind of thing humans have done for eons: counteract one effect with another. All we have to do is scatter about 700,000 metric tonnes (which is about 772,000 U.S. tons) of sulfur into the stratosphere each year for the first few years (and progressively more as time goes on) and the problem will be solved. Abracadabra! Presto-change-o! Warming-be-gone! Hurrah!
Oops! Sorry! My sarcasm filter slipped. Why the slippage? Because, because . . . because of a lot of things. One of the biggest is that dispersing sulfur in the atmosphere would do nothing to reduce carbon emissions; in fact, the sulfur dispersal would allow major polluters and other vested interests to continue denying the reality of climate change and fighting any measures that would limit emissions and put a dent in their profits. As the sulfur haze dialed down the Earth’s thermostat, it would dial down the political heat, as well. “Global warming? What global warming?” With temperatures falling, elected officials would be unlikely to impose unpopular measures to slash emissions and might repeal any limits that were already in place. As a result, there’s a good chance that greenhouse-gas concentrations would keep rising. What’s more, we’d get locked into pumping sulfur into the atmosphere ad infinitum, because, if we were ever to stop, the global average temperature would shoot up to what it would have been if we’d never engaged in the whole climate-hacking enterprise to begin with, and the subsequent, abrupt rise in temperature would be devastating.[iv] As Lennart Bengtsson, Senior Research Fellow at the University of Reading, put it: “the artificial release of sulphate aerosols is a commitment of at least several hundred years.”[v]
But what’s so bad about that? Would the cost of dispersing the sulfur be exorbitant? No, not at all. A study by Aurora Flight Sciences concluded that a fleet about the size of a small airline, like Jet Blue, would be more than sufficient to handle the job of delivering the sulfur to the stratosphere.[vi] Also, Teller, Hyde, and Wood speculated that a positive side effect of their plan would be such a large reduction in UV damage to skin and crops that the economic benefits would far outweigh the billion-dollar-per-year cost of sulfur dispersal.[vii]
Now, the above trio of venerated scientists (whom I want desperately to call Larry, Moe, and Curly Joe, but won’t because it would be disrespectful and inappropriate) seem to have overlooked a few of the negative side effects of sulfurizing the stratosphere, but here’s one that’s noteworthy for its irony: After the sulfur is injected into the heavens and begins to reverse global warming, global climate change will proceed unhampered. That statement might seem odd because we generally use the terms “global warming” and “climate change” interchangeably, but there is a subtle distinction between the two, as The Economist has noted:
Double the amount of carbon dioxide in the atmosphere and the average global temperature will go up. Add the right amount of stratospheric sulphur and the temperature will come back down to where it began. There will, in other words, be no net global warming. But though the average temperature is unchanged, the climate is not.[viii]
The results of multiple computer models indicate that, as a consequence of stratospheric sulfurization, the Earth’s average temperature would fall, but regional climates would go right on changing: The poles would get warmer, the tropics would get cooler, and droughts would occur more often. Studies show, in fact, that injections of sulfur dioxide into the lower stratosphere could disrupt summer monsoons in Asia and Africa, leading to crop failures and famines that could affect billions of people.[ix]
Which brings us to another whole set of problems. Computer models show that the effects of atmospheric sulfurization would vary around the world.[x] As a result, some countries would do better than others. Who would decide how much solar radiation to block? Might not billions of people facing drought-induced famines be a tad peeved if countries that stood to benefit proceeded with the plan? How much would subsequent wars cost? How much would we need to spend in foreign aid to try to prevent those wars? How much would human migration cost? Which countries would accept the immigrants? Teller, Hyde, and Wood estimated what they thought were positive side effects of pumping sulfur into the stratosphere, but they overlooked entirely the potential geopolitical costs.
They also ignored a number of environmental risks. One is the possibility of depleting the Earth’s protective ozone layer. Remember when the physicist-triumvirate said dispersing sulfur in the stratosphere would block some ultraviolet radiation and thus reduce skin disease and crop damage? Well, as it turns out, sulfate particles increase the ability of chlorofluorocarbons (CFCs) to destroy ozone.[xi] (CFCs, as you may recall, have been banned by international treaty precisely because they break up ozone molecules, create holes in the ozone layer, and allow more ultraviolet radiation to strike and damage skin and crops. Although we’ve largely stopped using CFCs, some that we used in the past are still drifting up to the ozone layer and some that are already there will keep destroying ozone for decades.[xii]) So, the scientific trio are very likely wrong-o. Rather than protecting us from skin disease and crop damage, stratospheric sulfate aerosols could exacerbate the depletion of the ozone layer and increase the prevalence of skin cancer and crop damage.
And there’s more bad news. The sulfate aerosols might also react with water molecules in the atmosphere to produce sulfuric acid, which could then fall as acid rain, snow, sleet, or particulates.[xiii] Acid precipitation damages soils, forests, buildings, statues, and monuments. It harms fish, frogs, snails, clams, and other aquatic creatures by making freshwater more acidic; and, as you might imagine, it’s no trip to the spa for human beings, either. Although it apparently has little impact on the outer surfaces of the human body, it affects our hearts and lungs when we breathe it in particulate form, and, in susceptible individuals, it aggravates asthma and bronchitis.[xiv] Beyond that, acid rain releases toxic metals from soil, transports them in water, and increases fish-eaters’ risk of consuming toxins along with their trout.[xv]
Ready for more?
Well, diffusing sunlight with stratospheric sulfur aerosols would reduce the amount of direct sunlight reaching the Earth’s surface—which is, of course, the point of pumping the sulfur out there—but it would also reduce the direct sunlight reaching solar panels. For that reason, it would have a negative impact on solar power production.[xvi] More diffused, less direct sunlight would also impact photosynthesis and the growth of plants.[xvii]
And the sky? Kiss sapphire and robin’s-egg blue goodbye.[xviii] According to a number of researchers, the daytime sky would undergo whitening and brightening.[xix] A depressing thought, isn’t it? Imagine living with the reality of a washed-out sky from here on out.
Okay. I’ve got a question for you: What happens if we’ve counteracted global warming by injecting enough sulfur into the sky to lower the average temperature of the Earth a couple of degrees and then Mount Pinatubo were to blow its stack again? Keep in mind that the cooling that followed its last major eruption inspired this whole farkakte scheme to begin with. What if Oregon’s Mount St. Helens, Indonesia’s Krakatoa, or Iceland’s Eyjafjallajökull (better known as “Mount Unpronounceable”) were to erupt at the same time? (Wondering how likely that is to happen, I did a little research and found that scientists have estimated a probability of about 37 percent for one mildly Earth-cooling volcanic eruption, and a 15-percent chance for two such eruptions over a ten-year span. When it comes to the eruption of one volcano with as much cooling potential as Mount Pinatubo’s 1991 eruption, the probability is in the range of 15 to 25 percent.[xx]) Might the Earth get a bit chilly if volcanoes belched sulfur into the stratosphere without our permission after we pumped a lot of sulfur out there on purpose? And if so, what in the world could we do about it?
* * * * * * *
Well, what do you say we return to our respective corners and ponder those questions for a while? In the interim, be sure to rest up, because next time we’ll consider whether global warming could be setting us up for more frequent volcanic eruptions in the future.
[i] Teller, Edward, Roderick Hyde, and Lowell Wood. “Active Climate Stabilization: Practical Physics-Based Approaches to Prevention of Climate Change.” Article submitted to the National Academy of Engineering Symposium. Washington, DC. April 18, 2002. Livermore, CA: University of California, Lawrence Livermore National Laboratory.
[ii] Libby, Stephen B., and Karl A. Van Bibber. 2010. Edward Teller Centennial Symposium: Modern Physics and the Scientific Legacy of Edward Teller. Hackensack, NJ: World Scientific.
[iii] Teller, Edward, Roderick Hyde, and Lowell Wood. “Active Climate Stabilization: Practical Physics-Based Approaches to Prevention of Climate Change.”
[iv] Ross, Andrew, and H. Damon Matthews. 2009. “Climate Engineering and the Risk of Rapid Climate Change.” Environmental Research Letters, Vol. 4, no. 4.
[v] Bengtsson, Lennart. 2006. “Geo-Engineering to Confine Climate Change: Is It at All Feasible?” Climatic Change. Vol. 77, p. 231. (Emphasis added.)
[vii] Teller, Edward, Roderick Hyde, and Lowell Wood. “Active Climate Stabilization: Practical Physics-Based Approaches to Prevention of Climate Change.”
[viii] “Geoengineering: Lift-off.” Economist. November 4, 2010.
[ix] Robock, Alan, Luke Oman, and Georgiy L. Stenchikov. 2008. “Regional Climate Responses to Geoengineering with Tropical and Arctic SO2 Injections.” Journal of Geophysical Research. Vol. 113.
[x] Robock, Alan. 2008. “20 Reasons Why Geoengineering May Be a Bad Idea.” Bulletin of the Atomic Scientists. Vol. 64, no. 2, pp. 14-18.
[xi] National Science Foundation. “Injecting Sulfate Particles into Stratosphere Could Have Drastic Impact on Earth’s Ozone Layer.” Press Release 08-069. April 24, 2008. http://www.nsf.gov/news/news_summ.jsp?cntn_id=111467 (Accessed November 30, 2013); “Geoengineering: Lift-off.” Economist.
[xii] Benedick, Richard Elliot. 1998. Ozone Diplomacy: New Directions in Safeguarding the Planet. (Enlarged Edition). Cambridge, MA: Harvard University Press: Manney, Gloria L., Michelle L. Santee, Markus Rex, et al. 2011. “Unprecedented Arctic Ozone Loss in 2011.” Nature. Vol. 478, pp. 469-475.
[xiii] Robock, Alan. “20 Reasons Why Geoengineering May Be a Bad Idea.”
[xv] Goyer, Robert A, John Bachmann, Thomas W. Clarkson, et al. 1985. “Potential Human Health Effects of Acid Rain: Report of a Workshop.” Environmental Health Perspectives. Vol. 60, pp. 355-368.
[xvi] Michael C. MacCracken. 2006. “Geoengineering: Worthy of Cautious Evaluation?” Climatic Change. Vol. 77, no. 3-4, pp. 235–43.
[xvii] Farquhar, Graham, and Michael L. Roderick. “Pinatubo, Diffuse Light, and the Carbon Cycle.” Science. Vol. 299, no. 5615, pp. 1997-1998.
[xviii] Hodges, Jim. “Geoengineering: Why or Why Not?” NASA Researcher News. April 7, 2008. http://www.nasa.gov/centers/langley/news/researchernews/rn_robockfeature.html (Accessed November 30, 2013.)
[xix] Kravitz, Ben, Douglas G. MacMartin, and Ken Caldeira. 2012. “Geoengineering: Whiter Skies?” Geophysical Research Letters. Vol. 39, no. 11; Robock, Alan. 2008. “20 Reasons Why Geoengineering May Be a Bad Idea.” Bulletin of the Atomic Scientists. Vol. 64, no. 2. pp. 14-18; Robock, Alan. “Bubble, Bubble, Toil and Trouble: An Editorial Comment. Climatic Change. Vol. 105, no. 3. pp. 383-385.
[xx] Hyde, William T., and Thomas J. Crowley. 2000. “Probability of Future Climatically Significant Volcanic Eruptions.” Journal of Climate. Vol. 13, no. 9, pp. 1445-1450.