If we're going to avoid climate disaster, we're going to have start getting a lot more direct. We're going to have to think about cooling the planet.
The concept is called geoengineering, and in the past few years, it has gone from being dismissed as a fringe idea to the subject of intense debates in the halls of power. Many of us who have been watching this subject closely have gone from being skeptics to advocates. Very reluctant advocates, to be sure, but advocates nonetheless.
What has changed? Quite simply, as the effects of global warming have worsened, policy makers have failed to meet the challenge. As a result, if we want to avoid an unprecedented global catastrophe, we may have no other choice but to reduce the impact of global warning, alongside focusing on the factors that are causing it in the first place. That is, while we continue to work aggressively to reduce the amount of carbon released into the atmosphere, we also need to consider lowering the temperature of the Earth itself.
To be clear, geoengineering won't solve global warming. It's not a "techno-fix." It would be enormously risky and almost certainly lead to troubling unforeseen consequences. And without a doubt, the deployment of geoengineering would lead to international tension. Who decides what the ideal temperature would be? Russia? India? The U.S.? Who's to blame if Country A's geoengineering efforts cause a drought in Country B?
Also let's be clear about one other thing: We will still have to radically reduce carbon emissions, and do so quickly. We will still have to eliminate the use of fossil fuels, and adopt substantially more sustainable agricultural methods. We will still have to deal with the effects of ecosystems damaged by carbon overload.
But what geoengineering can do is slow the increase in temperatures, delay potentially catastrophic "tipping point" events—such as a disastrous melting of the Arctic permafrost—and give us time to make the changes to our economies and our societies necessary to end the climate disaster.
Geoengineering, in other words, is simply a temporary "stay of execution." We will still have to work for a pardon.
Nothing New
Altering the Earth's temperature, of course, is hardly anything new. Human civilization has been changing the Earth's environment for millennia, often to our detriment. Dams, deforestation and urbanization can alter water cycles and wind patterns, occasionally triggering droughts or even creating deserts. On a global scale, industrial activity for the past 150 years or so has changed the Earth's atmosphere, threatening to raise average world temperatures to catastrophic levels, even if we were able to stop releasing carbon into the atmosphere immediately.
What we're talking about with geoengineering, however, is something new. It's a more deliberate manipulation of the environment, rather than a byproduct of other activities. And while we know more than we did just a few years ago about how it might work, there are still plenty of unknowns.
Geoengineering mainly takes two forms: temperature management, which moderates heat by blocking or reflecting a small portion of the sunlight hitting the Earth; and carbon management, which gradually removes large amounts of carbon from the atmosphere (as opposed to simply reducing the amount of additional carbon we're releasing into the atmosphere). Temperature management is the more likely course of action, as it has the advantage of potentially quick results, while carbon-management techniques that would have a global impact might take decades or centuries to show results.
Sun Block
Temperature-management proposals boil down to increasing how much sunlight the Earth reflects, rather than absorbs. (Increasing the planet's reflectivity by 2% could counter the warming effects of a doubling of CO2 emissions.) While a variety of techniques have been suggested, some don't pass the plausibility test, either due to cost, clear drawbacks, or both.
For instance, one proposal would place thousands of square miles of reflective sheets in the desert to reflect sunlight—an interesting plan, until you realize that this would effectively destroy desert ecosystems. Another proposal calls for launching millions of tiny mirrors into orbit, where they would block some sunlight from reaching the atmosphere. But one study of the orbiting-mirror plan concluded that, to keep pace with the continual warming, we'd need to launch one square mile of sunshade into orbit every hour.
Two approaches hold the most promise: injecting tons of sulfates—essentially solid particles of sulfur dioxide—into the stratosphere, and pumping seawater into the lower atmosphere to create clouds. A recent report in the journal Atmospheric Physics and Chemistry Discussions identified these two approaches as having a high likelihood of being able to counter global temperature increases, and to do so in a reasonably short amount of time.
The sulfate-injection plan, which has received the most study, is explicitly modeled on the effects of massive volcanic eruptions, such as Mount Pinatubo in the Philippines; in the months after the 1991 eruption, global temperatures dropped by half a degree Celsius.
To trigger a drop in global temperatures, we'd need to loft between two million and 10 million tons of sulfur dioxide (which combines with oxygen to form sulfate particles) into the lower stratosphere, or at about 33,000 feet. The tiny particles suspended in the atmosphere act like a haze, reflecting a significant amount of sunlight—though not enough to notice at ground level (except for some superb sunsets).
While this seems like a large amount, several studies have shown it could be done using some combination of high-altitude balloons, dispersal in jet-aircraft exhaust, and even more exotic platforms such as artillery shells. As with volcanic sulfates, the particles would eventually cycle out of the atmosphere, so we'd have to refresh that two to 10 megatons of sulfur dioxide roughly every year.
Stratospheric sulfate injection appeals to many geoengineering proponents for a few reasons. It doesn't require a massive leap in technology to carry out successfully; arguably, we could start doing it this year, if we needed to. It's relatively cheap, probably costing just a few billion dollars a year. And because stratospheric sulfate injection emulates an effect of volcanic eruptions, we already have some idea of what to expect from it—for better and worse. We know, for example, that the cooling effect could start within weeks of the injection process.
We also know that stratospheric sulfates will likely damage the ozone layer (as happened after Mount Pinatubo erupted), potentially resulting in more skin cancer and damage to plants and animals. In addition, the scattering of sunlight will reduce the efficiency of some kinds of solar power, and some studies have suggested that it could disrupt monsoonal rain cycles.
A Higher Chance of Clouds
The other high-impact proposal, cloud brightening, increases the amount of reflected sunlight by making more clouds and thickening existing ones. One idea is to use ships to propel seawater thousands of feet in the air, where it would form or increase cloud cover.
The technique has both advantages and disadvantages compared with the sulfate-injection method. Lofting seawater into the air to seed cloud formation would have fewer environmental side effects than the sulfates, and may allow for targeted use to counter droughts. Because it would be relatively low altitude, it wouldn't have the same scattering effect on sunlight as sulfate injection.
But increasing the extent and thickness of cloud cover could also have at least as powerful an effect on rainfall patterns as sulfate injection, increasing downpours in one area or contributing to unexpected droughts in others. Finally, the technologies required for cloud brightening are still experimental, though initial proposals look to be markedly more environmentally benign than those used for sulfate injection.
Both solutions could present a more dramatic problem if the geoengineering was to stop abruptly. According to some studies, global temperatures would spike once the geoengineering steps were ended, actually exceeding for a short time where they would have been without any geoengineering. Afterward, the temperature increase would continue as if nothing had been done to slow it. While this doesn't mean we'd have to undertake geoengineering indefinitely, it underscores why geoengineering must be accompanied by carbon cuts.
Also, neither would do anything to solve other problems that arise from excessive levels of carbon dioxide, such as oceans becoming more acidic from increased carbon loading.
The Political Impact
Any kind of geoengineering would also face other issues. Most prominent are the political concerns. Since geoengineering is global in its effects, who determines whether or not it's used, which technologies to deploy, and what the target temperatures will be? Who decides which unexpected side effects are bad enough to warrant ending the process? Because the expense and expertise required would be low enough for a single country, what happens when a desperate "rogue nation" attempts geoengineering against the wishes of other states? And because the benefits and possible harm from geoengineering attempts would be unevenly distributed around the planet, would it be possible to use this technology for strategic or military purposes? That last one may sound a bit paranoid, but it's clear that any technology with the potential for strategic use will be at the very least considered by any rational international actor.
There are also more mundane questions of liability. If, for example, South Asia experiences an unusual drought during cyclone season after geoengineering begins, who gets blamed? Who gets sued? Would all "odd" weather patterns be ascribed to the geoengineering effort? If so, would the issue of what would have happened absent geoengineering be considered relevant?
Consider the Alternative
With all of these drawbacks, why would I consider myself an advocate of geoengineering, no matter how reluctant? Because I believe the alternative would be worse.
The global institutions we rely on to deal with a problem like climate change seem unable to look past short-term roadblocks and regional interests. At the same time, climate scientists are shouting louder than ever about the speed and intensity of environmental changes coming from global warming.
In short, although we know what to do to stop global warming, we're running out of time to do it and show no interest in moving faster. So here's where geoengineering steps in: It gives us time to act.
That's if it's done wisely. It's imperative that we increase funding for geoengineering research, building the kinds of models and simulations necessary to allow us to weed out the approaches with dangerous, surprising consequences.
Fortunately, the deployment of geoengineering need not be all or nothing. Though it would have the greatest impact if done globally, some models have shown that intervention just in the polar regions would be enough to hold off the most critical tipping-point events, including ice-cap collapse and a massive methane release.
Polar-only geoengineering strikes me as a plausible compromise position. It could be scaled up if the situation becomes more dire and could be easily shut down with minimal temperature spikes if there were unacceptable side effects.
Still, we can't forget: Geoengineering is not a solution for global warming. It would simply hold temperatures down temporarily, doing nothing about the causes of climate change, let alone ocean acidification and other symptoms of a carbon overdose. We can't let ourselves slip back into business-as-usual complacency, because we'd simply be setting ourselves up for a far greater disaster down the road.
Our overall goal must remain the reduction and then elimination of greenhouse-gas emissions as swiftly as humanly possible. This will require feats of political will and courage around the world. What geoengineering offers us is the time to make it happen.
--Mr. Cascio, based in the San Francisco Bay area, is a futurist and Senior Fellow at the Institute for Ethics and Emerging Technologies. He can be reached at reports@wsj.com.
Posts
