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Can we cool the earth through geoengineering?

This is a long article, but a good read. It is the best paper I have read on using geoengineering to address climate change. It takes a comprehensive look at all the possibilities and gives an analysis of how likely they are to produce results and the challenges associated with them. Without giving away too much, don’t give up of the need for aggressive mitigation measures anytime soon.

~ Barry Vesser


Engineering the Climate: Can we stave off global warming by tinkering with the planet?

By Powell Hutton

January 2016

Powell Hutton served for 30 years in the US Army, after which he worked in the public and private sectors, including doing research and analysis for the Departments of Defense and Energy. This article is based on a recent talk he gave for former World Bank staff. It first appeared in The American Oxonian, Fall 2015, vol. CII:4. Major sources include Earthmasters (Yale 2014) by Clive Hamilton; the online publication Yale environment 360; and online sources including the National Oceanic and Atmospheric Administration, the Intergovernmental Panel on Climate Change, and the National Aeronautics and Space Administration.

The December 2015 climate change conference in Paris was a major breakthrough after decades of talk. Never had the world achieved such a broad international consensus to cut back carbon emissions. In political terms, part of the reason for its success was that each participating nation set its own voluntary goals to cut emissions, with no external legal enforcement mechanism other than international opprobrium. Each country offered its own carrot. But there is no stick.

In environmental terms, the Paris agreement didn’t go far enough. Most careful observers say the combined efforts, unless decidedly ramped up in the near term, will ultimately fall short of the goal of keeping the Earth’s temperature from rising beyond 2 degrees Centigrade since the Industrial Revolution, let alone the more aspirational goal of 1½ degrees.

How do we meet the voluntary Paris goals, let alone the ramped up ideal? The push to curb global greenhouse gas emissions is the most important and direct way to moderate rising global temperatures: cutting back on the prime causes over which humans have control. Let’s call this emphasis on mitigation, Plan A.


The real practical, political, and economic difficulties in implementing Plan A, however, have led to increasing interest in alternative solutions. Maybe we can wriggle out from doing the difficult parts of Plan A by circumventing them. Instead of cutting emissions directly, can we manipulate the Earth’s climate to counteract global warming in a Plan B? That way we could have our cake and eat it, too. So, yes, there is a Plan B, and it’s called “geoengineering,” or human attempts to shape the Earth’s climate to suit our wants.

A good definition of geoengineering is the deliberate and large-scale intervention in the Earth’s climatic system with the aim of reducing global warming and its effects. While it has been studied since the 1970s, a lot more money and research is going into it now, and Plan B has become a topic of growing public interest, if not hype. Almost immediately after the Paris agreement, for example, we started hearing about Plan B from major news organizations. In a four-part segment, National Public Radio said geoengineering approaches would be needed to keep temperatures down. The Washington Post ran an opinion piece arguing that geoengineering “can and should go hand in hand with natural defense plans.”

The danger is that the more we talk about Plan B, the less we will perceive the need to follow through with the Paris agreements and Plan A. Geoengineering, however, in spite of what some of its most ardent backers say, is far from shovel ready. In fact, we need a lot more study of the consequences before we even think about buying the shovels.

There are two broad avenues of research. One calls for sucking carbon dioxide out of the atmosphere to decrease the greenhouse effect. Let’s call that B1. And the other approach is to manage the amount of sunlight coming in, so we don’t get so hot. Let’s call that B2.

Human imagination and ingenuity have produced at least 40 different ways to do these jobs. Some are simple, like painting roofs white—or, on a larger scale, painting mountains white. Some are downright wacky, like digging up and scattering moon dust to orbit around the Earth to shade us from the sun. At least that’s more interesting than merely deploying large mirrors in space to reflect heat back out. My personal favorite is to increase the Earth’s orbit by 1 to 2 percent. That’s been calculated to add five and a half days to the year. I don’t know what it would do to other planetary orbits, and I don’t think the proponents do either. That’s the rub with all these ideas—we don’t yet understand, let alone know how to cope with, the unintended consequences of our tinkering. Our global systems are just too complex. Please keep this caveat in mind, because we are literally dealing with life and death.

So let’s look at the first line of attack, Plan B1: absorbing carbon. Vegetation lives and dies, and while it’s growing, and during the day, it soaks up a lot of carbon—but it also gives up a lot when it dies. The net effect, however, has been a good one for the climate. Trees are excellent for this job, but global reforestation is unlikely to be effective in the short term, because current deforestation is so extensive and prevalent. Deforestation now accounts for some 11 percent of global emissions, a trend that would first have to be reversed. Underscoring the difficulty is that warming has allowed insect populations to extend their ranges and seasons into boreal forests. In British Columbia, for example, 80 percent of the mature lodgepole pine forests have been destroyed by the mountain pine beetle. Those forests are now carbon sources, not carbon sinks.

Sequestration underground is another way to soak up carbon, and it might handle up to half of human-produced CO2, namely that emitted from large industrial sources. Attacking the problem there is advantageous, because CO2 is some several hundred times more concentrated out of a power plant smokestack than in the atmosphere.

Pilot plants have been built to test the viability of carbon capture and storage (CCS), but they’ve had a mixed record, and no full-scale power plant with CCS is yet in operation. Sequestration uses energy, it’s expensive, and it can be risky. The extra energy needed to run the process either reduces power output significantly—perhaps by a third—or requires its own separate source, creating more emissions and increasing power bills. CO2 can be and has been pushed back down oil or other wells, but coal-fired plants aren’t always located in the best places for that. The endeavors have been relatively accident-free so far, but because of the pressures needed, the potential for leaks is always present. In its present form of maturity, CCS is unlikely to contribute significantly to mitigating global warming.

That leaves the oceans, which already do most of the work in absorbing carbon out of the atmosphere. They cover three-quarters of the Earth’s surface and work 24/7, not just in daylight hours as with reforestation. The challenge is that the top layers of the ocean are already have a full charge of CO2, so how can we change that?

One way is to improve absorption in the surface waters through what’s called ocean fertilization. Iron is a necessary ingredient for photosynthesis, and is often the limiting nutrient, so if we can throw enough iron filings or iron sulfate slurry into the water, we can foster the growth of algae, which will absorb more CO2, and some of the carbon might sink below the topmost layers.

The return on investment looks really good in the lab. One ton of iron can theoretically promote the absorption of between 30,000 and 110,000 tons of CO2. It’s a little hard to visualize just what such numbers mean, but they look big and they look good—a good ROI.

OK, where to put this iron? Cold water absorbs more CO2 than warm water, so placing iron in Arctic or Antarctic waters would be more effective than off Hawaii. Wherever we do it, though, we run into the traditional problem of algae blooms everywhere. In the process of sucking out CO2, growing algae also suck oxygen out of the water, creating dead zones such as we have in the Chesapeake Bay and in the Gulf of Mexico at the mouth of the Mississippi. Fertilization and the resulting blooms upset the biological and mineral balance of nutrients in the ocean, and on a global scale we don’t really know what that would do to existing fish and mammal stocks, but it is unlikely to be positive.

To test out iron fertilization, since the early 1990s over a dozen experiments have been conducted in the Antarctic’s Southern Ocean. It’s cold and it’s deep, yet the results have been uniformly disappointing. Experiments altered the chemical composition of a few hundred square kilometers of water for just one or two days. Instead of the proportional equivalent of 30,000 to 110,000 tons of absorbed carbon, only the proportional equivalent of 200 tons was measured.

Moreover, iron’s effectiveness will change over time, as the ocean becomes warmer, fresher, and more acidic—warmer, because green water with algae absorbs more heat than cleaner blue water; fresher, because of ice melt; and more acidic, because in the water, CO2 turns into carbonic acid. Very major and repeated infusions of iron would be necessary to have a sustained global impact. Even so, revised calculations indicated that the ocean could extract only about 3 percent of current emission output. It wouldn’t touch what’s already there.

To combat ocean acidification, with its destructive effects on marine ecosystems, crushed limestone could be added. But the massive amounts needed would require a whole new mining, transportation, and distribution infrastructure. Iron fertilization would need its own new infrastructure as well. The net impact of these new major industrial loads on the environment would counter-balance the carbon savings they were trying to promote. Of course, we also haven’t figured out who would foot the bill.

Two final points about Plan B1. First, this approach attacks the problem of CO2 head on, by trying to get rid of CO2 in the atmosphere. That’s good. Second, though, it takes a long time. Natural absorption is not a quick process. It can’t be implemented globally and be effective in a short time. That’s not so good.

To do something quicker, or to act in a climate emergency, we’d have to look to the second approach, B2, solar radiation management—to reduce the heat from the sun before it heats up our atmosphere. Once again, oceans hold the key, because water absorbs and keeps heat much more effectively than air. The shortfall of this approach, however, is that if all we do is cut back on sunlight, CO2 build-up and ocean acidification continue unabated. If done well, however, B2’s effects could be almost immediate.

There are three major ideas, and they play off the different wavelengths of incoming and outgoing (or reflected) infrared radiation. The first is to cool us by opening a window in the sky. The highest cirrus clouds act as a blanket to hold in more heat than they reflect back out, so if we got rid of them, more of the Earth’s heat would escape. This might be done by adding special chemicals to jet fuel. But this idea hasn’t gained much ground.

The second idea is the reverse. Instead of removing the high clouds, we’d add low clouds over the oceans: by brightening the total marine cloud cover, we reflect more heat back into space and might keep the oceans from absorbing so much. By one estimate, 1,500 ships, each configured with 28 billion—that’s billion with a B—sub-micron level nozzles could spray sea water into the atmosphere to provide nuclei for cloud droplets to form and increase the cloud cover. The biggest assumptions and unknowns involve cloud dynamics, about which our knowledge is frankly very limited.

Perhaps the most widely discussed concept is to shade us by spraying aerosol particles, typically sulfur dioxide, up into the stratosphere where they would likely remain for some weeks before needing to be replaced. The idea takes its roots from volcanic eruptions, which have proved to be very effective sun shields. Tambora in 1816, Krakatoa in 1883, and more recently Pinatubo in 1991, all ejected massive amounts of sulfate aerosols high enough into the atmosphere to substantially cool the Earth for a significant time. Some 60 years ago, this was the type of effect that led to fears of a “nuclear winter.” The actual technology needed to deliver man-made aerosols does not appear to be a big obstacle, at least compared to other options.

Before we get too enthused about these possibilities, let’s take a closer look. CO2 spreads rapidly, and more or less uniformly, around the globe, providing a blanket to keep the heat in all the time. Cloud formation and reflection, however, would be patchy, effective only in daylight, and more effective in the tropics where the sun’s rays are strongest. Thus, a cloud shield near the equator could drop temperatures there by about 0.5 degrees Centigrade. It would have marginal effect at the poles, however, because the sun’s rays are more oblique. The more uniformly dispersed CO2 would more than offset the reflectivity of the clouds, such that even with a cloud shield the temperature at the poles might increase as much as 1 to 2 degrees Centigrade. That’s enough to melt a lot of ice—and polar ice is the key driver on all estimates of our future climate.

I mentioned earlier the importance of acknowledging unintended consequences. In that classic imagery, would the flight of a butterfly let loose on one side of the world cause a typhoon on the other? Changing the climate in one region has implications elsewhere we cannot fully anticipate. As Don Rumsfeld might say, we have unknown unknowns.

We know, for example, that man-made stratospheric clouds would be cooling, but we also know that in so doing they would cut rainfall. Creating a more consistent tropical cloud cover over the Amazon Basin could cause up to a 20 percent drop in rain there. That would have a fundamental impact on the character and composition of the rain forest, affecting tree growth and thereby CO2 absorption. Models indicate it could cause a 10 to 20 percent drop in rainfall in the United States, enough to give the Southwest, already in a major drought, even more pause. Russia would likely receive some 10 percent less rain.

More importantly, models tell us that cooling Central Asia could interfere with current cloud and heat patterns and change the monsoons, thereby directly affecting the food sources for over two billion people in South and Southeast Asia. We’re already reading about the problems with rainfall from which Pakistan, India and Bangladesh have been suffering. Are we willing to risk upsetting the monsoon cycles on which so much life—human and other—depends?

Adding sulfur would also certainly lead to an increase in air pollution, already a costly global health issue. Ironically, if China, India, and all the others, including the United States, were to clean up their air pollution overnight and suddenly give us all clear skies, world temperature would rapidly increase by almost 1.1 degrees Centigrade, more than the 0.8 degrees Centigrade we’ve had globally since the Industrial Revolution.

Underscoring that projection, we got direct evidence after the 9/11 attacks, when all flights over the United States were cancelled for three days. During that period, with virtually no contrails across the continent, the average daily surface-level temperature range across the country increased by about 2 degrees Fahrenheit above the climatological average. The response to removing those clouds was very quick. In short, modulating sunlight can be very effective.

So we’re at what Clive Hamilton, an Australian professor and author of Earthmasters, calls an “exquisite dilemma.” Having low-level sulfate pollution from burning coal and oil actually cools the planet. Yet the World Health Organization estimates that 1.3 million people die every year from this thick brown haze. Should we warm up the planet to reduce asthma deaths?

This quandary leads to another sobering thought. If we ever were to deploy an effective sun shield, we might have to do it indefinitely. Any disruption in continuous shielding that might occur from, say, budget difficulties or international turmoil, could cause an immediate sharp spike in global temperatures that would be prolonged for decades.

Let’s look at what such a sharp spike might mean. Gardeners in northern Virginia know that when August gets too hot, the tomatoes they harvested in July won’t be back again until September. The fruit doesn’t set when the temperature is regularly much over 85 degrees Fahrenheit (or 30 degrees Centigrade). This phenomenon has global food consequences. In Southeast Asia, rice production goes down about 9 percent for every increase of 1 degree Centigrade in nighttime averages; it’s the nighttime resting temperature that is key. Agronomists in Australia found that wheat production showed a potential decrease of up to 50 percent if the temperature rose by about 2 degrees Centigrade. Heat stress similarly affects corn and soybean production.

We might cope with such a rise if we could replant higher up the mountainsides or in cooler climes closer to the poles, but such options are not available on a global scale. Diminished fresh water supply compounds the issue. Bioengineered heat- and drought-friendly crops are unlikely to keep up with the pace of projected climate change.

And of course, such options are not available to non-agricultural plant life. Ecologists stress that the rate of warming is more important than the amount of warming. Animals can migrate, and given enough time, plants can adapt. In fact, they have and they are. Around the globe, species are on the move, climbing in elevation about 36 feet and moving poleward about 10 kilometers per decade to escape the heat and stay within their niches.

Whole ecosystems, however, cannot. The birds that migrate to the Arctic tundra in the spring have evolved their timing to synchronize with the bloom of insects, a rich food source for their young. With earlier warming of the Arctic, however, the insect population may have reached its peak before the birds arrive. An article I read some years ago described the vanishing of the snowshoe hare in Montana and Idaho because the snow was coming later than in previous years. The snowshoe hare turned white on its evolved schedule—not the new delayed snow schedule—and, before the snow arrived, he was a prime target for predators, white against a brown background.

These are small, two-step imbalances. They are replicated and magnified along a complex, multidimensional stairway of global scale. When you look at whole ecosystems—that is, from plants, their flowers and fruits, to pollinators, herbivores, and carnivores, up, down, and across the food web that represents our planet’s rich but diminishing biodiversity—studies have indicated that if the temperature increases at a rate of 0.1 degrees Centigrade per decade, about half of the ecosystem can adapt. If the temperature rises at 0.3 degrees Centigrade per decade, only about 30 percent can adapt, and of that, only 17 percent or about one-sixth of forest ecosystems can adapt.

In other words, if we ever decide to remove the sun shade in a hurry or falter in keeping it there, few ecosystems would survive. Even if ecologists are only half right, is that a risk we are willing to take?

Stratospheric aerosol spraying is the archetypal geoengineering technique—a technofix that would be easy, effective, cheap, and have the most far-reaching implications for all life on Earth, not just human life.

So where are we? Multiple lines of attack that are not mutually exclusive and can complement each other are usually better than just one.

Plan B1—soaking up carbon—attacks the CO2 problem directly. Reforestation and carbon capture and storage deserve our continued full support. But overall, Plan B1, especially oceanic intervention, looks very expensive, would require a major industrial mobilization, have a limited global effect, and take a long time for results—probably too much, to do too little, and too late.

Plan B2—managing the sun’s radiation—has the promise of a smaller industrial and budget outlay, could be deployed reasonably quickly, would affect global climate patterns, and have an immediate effect on reducing heat. If deployed, however, it would probably have to be continued almost indefinitely. It would substantially affect food sources and availability, and it certainly wouldn’t deal with a continuing build up of CO2 or with ocean acidification.

Let’s look at a few other issues.

What is a looming catastrophe for some is a booming opportunity for others. The Dutch are delighted at the marketing prospects for their sea-wall expertise. Russians happily anticipate a Siberian breadbasket. Some Brits are even looking to create a new Champagne district in Kent’s chalky soil. Newly accessible oil and gas reserves in the Arctic provide long-term opportunities. Consider the shortened trade routes between Europe and Asia. Canada wants to ensure the Northwest Passage stays open and under its control. The Northeast Passage above Siberia had 74 transits in 2013, up from just two by icebreakers a couple of years earlier.

If we were to refreeze the Arctic, that bellwether of climate change, and to engineer our climate back to “normal” (and, by the way, how to define that? Is it 50 years ago, or as of last quarter’s financial statement?), a number of entrepreneurs—and politicians—would be quick to register their opposition. Not least, there is that defining capitalist mantra, “No infringement on economic freedom.” Plan A, cutting emissions by mandate, taxes, or otherwise, is Exhibit No. 1 for infringing on economic freedom, one of the reasons there’s been so little headway on it. Plan B, however, would be equally infringing. Both need regulation.

Right now, there’s not a lot of that. In the absence of a strong international lead, or indeed a lead from the government of any industrialized nation, the geoengineering field has been left wide open to actors from the private sector. Bill Gates is a leading financial supporter of technologies with promise. The oil majors are deeply involved in studies and experiments. Universities are in on the act. Everyone is seeking patents on their ideas, and patents are being recorded on the books far faster than either law or regulation can keep up. It’s fair to ask, without too much cynicism, will the fate of the Earth be in the hands of one or two private companies or individuals that hold the legal rights and the technological levers to changing the climate?

Humans have always wanted to control the weather. But rain dances and cloud seeding have so far been local, not global, efforts, and they usually failed to deliver on their promise. If we ever get there, though, who will or who should control the knobs on the global climate thermostat? In spite of a UN convention against it, some analysts project future weather wars, where one strongman closes down the life-giving rain of his enemy—though that seems a bit far fetched, at least for now. In any case, India might not like its growing seasons affected by decisions made in Washington, Moscow or Beijing—or by a Monsanto, Gazprom or Samsung either.

Geoengineering is much more than a technofix to climate change. At its heart, it is a double-barreled moral question—a question of justice between the current developed and developing worlds, and a question of justice between our generation and future ones. The starting point is our failure so far adequately to address head on the scientific warnings of global warming. Geoengineering has been advanced as Plan B to buy time while we sort out Plan A, and it’s a cheaper fix. It is not, however, a substitute.

In practice, geoengineering has been used by some of the biggest fossil fuel emitters—coal, oil, gas, and automotive interests—as a way to reduce incentives to cut CO2 emissions and to delay Plan A implementation. Up until 2006, for example, ExxonMobil had given $1.9 million specifically to fund anti-climate studies by the Heartland Institute, a think tank spun off from the American Enterprise Institute. The donations were specific enough for the UK’s Royal Society to ask ExxonMobil to stop funding studies that have “misrepresented the science of climate change by outright denial of the evidence.” That funding stream has stopped, and to his credit, the current Exxon CEO has publically acknowledged that man-made fossil fuel emissions contribute to global warming.

It’s perhaps easy to poke at the big guys. Fundamentally, though, we’re all responsible for global warming, especially those of us in the developed world. Even if we ourselves are not big emitters, we willingly feed off those who are. As Pogo said, “We have met the enemy, and he is us.” It is up to all of us, not just a few, to take action.

Geoengineering is a case where we are trying to have our cake and eat it too. The CO2 we’ve put into the atmosphere so far will be there for centuries and will continue to heat up the globe by about another 1 degree Centigrade, even if we were miraculously to add no more from now on. We’ve taken the benefits of fossil fuels now at the expense of poorer societies and future generations. Geoengineering risks making similar mistakes.

We humans as a species, if not all individuals, will probably survive, because we are exceptional adapters. Not every living thing on this planet is. And unlike us, they won’t have a say in their future. Can the energy, optimism, and entrepreneurial spirit that have gotten us this far now be used to recognize the long-term issues that we—and our life partners on the Earth—face, and do the right thing?

Let me close with another quote from Clive Hamilton. He says: “The essential message is that when we mess with ecological systems, things soon become much more complicated than they first seem, and as the complications multiply so do the uncertainties and dangers.” Plan B, geoengineering our Earth’s climate, as we now understand the options, is not an answer to our inability to address Plan A. We’re likely to hear a lot more about geoengineering in the months and years ahead as a good response to global warming. It’s worth continuing investigation, but it’s not ready for prime time.

In the meantime, Plan A, cutting emissions, is where our real efforts should lie and the earlier the better. We know what CO2 does in the atmosphere, how much is there, where it’s coming from, what it’s interactions are, and that we humans are throwing the natural balance out of order.

That balance is very finely tuned. When I was in high school, I learned that CO2 represented just 0.03 percent of air. Now it’s 0.04 percent or 400 parts per million. That doesn’t sound like much of an increase, but it has major consequences. Another example: average ocean pH is just 0.1 lower than in pre-industrial times. Even allowing for regional variations, NOAA estimates that 30 percent of the waters off the coast of the US Pacific Northwest are now too caustic to permit the survival of the zooplankton at the bottom of the food chain for herring, mackerel, salmon, King crabs, and Alaskan oysters. We ignore the natural balance at our peril.

Paris was a major step forward, but much remains to be done. The United States, for its part, can and has started to provide leadership by example to correct a problem that we have all too freely helped create over the past century, but we need to do more and that will be painful. We have a lot of work to do and it will take a lot of money, but not nearly what doing business as usual would cost—in lost opportunities, lost treasure, and lost lives.