Options for engineering the climate system, some long-dismissed by many as a vestige of Buck Rogers, are getting additional attention as near-term prospects for an effective political remedy remain bleak. But with research into the subject come increasing numbers of ethical questions yet to be resolved.

Is geoengineering an ethical response to the problem of climate change? What moral issues are raised by any deliberate manipulation of the climate system? Should research into its science and engineering proceed, or does that step create a moral hazard by making emissions cutbacks seem less urgent?

There are more questions, to be sure, and few easy answers. But scientists, environmentalists, and philosophers increasingly are grappling with the complexities and tradeoffs of climate solutions long considered by many to be drastic, as they fear the world seems unable or unwilling to get carbon out of its energy diet.

This first of a two-part series examines geoengineering and its potential side effects, including recent studies that find the costs are relatively small. Part two will explore some of the ethical questions being raised about geoengineering by philosophers, scientists, and others.

Engineering the Climate

Geoengineering, also called climate engineering, involves the deliberate modification of Earth’s natural systems to reduce global warming. The term itself is not vanilla and all-encompassing, and not all geoengineering proposals are alike.

Grand ideas have been bantered about for decades — mirrors in space to deflect a portion of incoming sunlight, or injection of sulphur particles in the upper atmosphere to mimic the cooling effects of large volcanic eruptions. Spreading iron dust in ocean eddies could act as fertilizer for phytoplankton, whose blooms and death would drag carbon into the deep ocean. Other proposals include spraying seawater to brighten marine clouds and reflect sunlight, or painting some large number of roofs white.

These schemes can be cheap and certainly cost-effective. In some cases, they can also be fast, but they are hardly without risks. In the last few years scientists have been putting foundations under these ideas, especially since the failure of the 2009 Copenhagen climate summit and with limited success in subsequent international negotiations. As the observed effects of climate change — which, remember, are still in their infancy — become apparent, and as the future looks ever more foreboding, there is an expanding sense that solutions once thought radical may one day be necessary, and that the research needs to be under way now. Private parties have already undertaken geoengineering experiments, with permission or without, with no small controversies.

Born from Pessimism over Policy Prospects

Like an artery-clogged person who doubles down on the pizzas, Earth’s most intelligent species is gulping fossil fuels at an ever-increasing rate, despite all the warnings from the world’s scientific communities. Prospects for significantly reducing carbon emissions through international protocols for some have never looked more bleak, and cutbacks on the scale needed to halt dangerous climate change — at least 80 percent — look nearly unreachable.

The resulting gloom, and the threats of a climate emergency — rapid disintegration of the polar ice sheets, massive methane burps from frozen tundra, unforeseen black swans that change the game — leave geoengineering as a fallback position, the last arrow in the climate quiver.

As science writer Eli Kintisch wrote in his 2010 book Hack the Planet, “geoengineering is a bad idea whose time has come.”

Two Geoengineering Acronyms: CDR and SRM

Geoengineering schemes fall into two broad categories: carbon dioxide reduction (CDR) such as sequestering carbon in the oceans or extracting it directly from the air; and solar-radiation management (SRM) — reducing how much sunlight hits the planet’s surface. Most of the promise — and most of the controversy — lies in SRM schemes, which are fast, cheap, imperfect, quasi-permanent, and could be done unilaterally by a country or an organization.

Just a few grams of sulphate particles delivered to the stratosphere, costing about a dollar per kilogram, could offset the warming of a tonne of carbon dioxide; this century’s warming could be reduced at least one hundred times cheaper than by emissions cuts. A 2010 opinion article by David Keith, Edward Parson and M. Granger Morgan in the journal Nature observed that “SRM may be the only human response that can fend off rapid and high-consequence climate impacts.”

Breaking the Geoengineering Research Taboo

But not long ago, simply talking about geoengineering was taboo.

While science titans like Edward Teller and John von Neumann had pitched climate modification as a weapon in the Cold War, one of the first efforts to examine the options critically was a 1992 paper in the American Geophysical Union publication EOS by David Keith and Hadi Dowlatabadi. Even though the climate problem was becoming clear – the United Nations Framework Convention on Climate Change was founded that year — many in the climate community appeared reluctant to discuss it because of its “moral hazard” problem: the concern that if climate engineering came to be seen as a tenable solution to climate change, avoiding the problem in the first place through reductions in emissions of greenhouse gases would be second-fiddle.

But the topic was peeled open for discussion by Paul Crutzen’s 2006 editorial essay in Climatic Change calling for active research into geoengineering, especially by changing the Earth’s albedo by releasing aerosols into the stratosphere. Crutzen’s reputation and scientific heft — he was awarded a share of the 1995 Nobel Prize for his work on atmospheric chemistry and ozone depletion — made the topic respectable, and research has snowballed since (see Sidebar).

In many ways, carbon dioxide reduction (CDR) is the more preferred of the two geoengineering avenues. While it might appear crazy (not to mention expensive) to be extracting carbon-based fuels from the ground only to then recover their carbon for burial, such schemes avoid most of the carbon problem in the first place, such as acidification of the oceans or plant overgrowth that would change the Earth’s reflectance.

Unfortunately, iron fertilization proposals are likely limited to relatively small reductions of a couple of gigatons of carbon per year. With the world now emitting 11 gigatons annually as a result of burning fossil fuels, cement production, and land use changes, warming could only be partially delayed at best. Unlike with SRM, fertilization schemes have been prototyped by those hoping to sell carbon credits, most notably the LOHAFEX experiment in the southwestern Atlantic ocean in 2009, and this past summer’s controversial (and much condemned) iron dump off the coast of British Columbia by a California businessman.

By contrast, SRM schemes could bring a world with high carbon dioxide but low temperatures — a new, unnatural planetary state. Agricultural productivity would probably rise, but the oceans would still have high acidity, and there could be regional precipitation changes. Climate engineering by the creation of stratospheric clouds could lead to a reduction of the summer monsoon precipitation over India and China, while marine cloud-brightening could bring pernicious impacts to the Amazon, with precipitation reductions of up to 50 percent. (Both reduce incoming shortwave radiation from the sun, and the cooler surface evaporates less.)

For example, the 1991 eruption of Mt. Pinatubo in the Philippines put about 17 million metric tonnes of sulfur dioxide into the stratosphere, and for the next two years average temperatures in the Northern Hemisphere were about 0.6 degrees Celsius cooler, and down 0.4 – 0.5 degrees C globally. Over the subsequent year and a half, global land precipitation dropped by about 6 percent (see Figure) — 4 cubic miles less rainfall, every day.

Figure: The June 1991 eruption of Mt. Pinatubo resulted in a noticeable drop in global land precipitation (right-hand axis) of about 0.2 Sv (1 Sverdrup = 106 cubic meters per second) and global river discharge (left-hand axis). From Hegerl and Solomon (2009) after Trenberth and Dai (2007). Credit: AAAS and AGU. Used with permission.

Another complication is that sulfur dioxide in the atmosphere mixes with ambient water and oxygen to become sulfuric acid, which in turn triggers acid rain and contributes to ozone depletion.

Worse, a serious SRM effort could not be quickly discontinued without serious consequences. Think of lifting the lid on a boiling pot: Unprecedented rapid and dangerous increases in world temperature would take place in as little as two decades if our descendants, or theirs, stopped geoengineering.

More Specific Research… and  More Ethical Considerations

Research into geoengineering is getting ever more specific, and in so doing bringing the ethical issues to light.

For one, it’s now clear that deploying SRM by injecting aerosols into the upper atmosphere (stratosphere) would be quite cheap. A recent engineering cost analysis by McClennan, Keith and Apt concluded that the anticipated extra climate forcing over the next 50 years could be offset with existing technology at a cost of less than $8 billion per year.

That’s cheap enough that a single government could do it, even a small (or rogue) country concluding climate change will become intolerable and giving up on any global consensus, regardless of the deployment’s effect on others. (It’s also well within the financial capabilities of many large corporations.) It all conjures up the notion of fighter jets some day being scrambled to take down tanker jets sent aloft to spray aerosols, or taking out balloons carrying up hoses for a “StratoShield.”

Another recent study looked at the possibilities of local SRM to combat regional heat waves. Diana Bernstein of Hebrew University and colleagues looked specifically at a 2006 heat wave over central California, which lasted for over two weeks and led to the deaths of an estimated 170 people. They found that daily injections of about three kilotons of sulphate aerosols over small regions (about 100 to 1000 square kilometers) led to a 7 ºC (13 degrees F) reduction in mid-day temperatures. Such an effort could require on the order of 100 C-5 cargo jets. However, the researchers note the possibility of unwanted side effects on local or nearby temperatures, such as changes in rainfall or ozone depletion. Sunshine-starved Oregonians might not like the thought of a California aerosol cloud bleeding over their wonderfully warm summer days.

Geoengineering would take climate justice one step higher. Any large geoengineering effort, especially SRM, is going to elicit cries, and of course lawsuits, from those who believe they are harmed, whether the weather events they experience are natural or not. And climate science, still struggling mightily with attribution of extreme weather events like Hurricane Sandy or the midwestern U.S. drought, may not — and may never — be able to provide unequivocal findings.

But more research may not be the answer to the geoengineering conundrum. “I think the biggest problems are not technical,” says Harvard’s David Keith, “but really are trying to understand how on Earth we would have a legitimate system of governance that would be able to make decisions about implementation.”

In part two, to be posted during the week of December 19, some of the philosophical issues raised by climate engineering will be examined. It will also address new ethical questions geoengineering raises beyond the moral problems that stem from humans’ changing of the climate.

Studies on Geoengineering

Contrary to the myth that scientists in the 1970s were convinced about an impending ice age, a 1965 report for President Lyndon B. Johnson warned of a CO2-warmed world — and offered (page 127), as its only solution, two geoengineering ideas to reflect solar radiation. Three reports by the National Academy of Sciences — in 1977, 1983 and 1992 — all discussed geoengineering as a possible response to the CO2issue.

Since Crutzen’s “geoengineering as escape valve” paper in 2006, a series of reports and special journal issues have been examining geoengineering from ever more angles, including a 2007 conference on iron fertilization of the ocean at the Woods Hole Oceanographic Institute in Massachusetts, a 2009 study by the UK’s Royal Society, a special issue in 2012 of the Philosophical Transactions of the Royal Society A, and a series of philosophical essays on the ethics of geoengineering by SRM in the Ethics, Place & Environment. Even the Vatican has considered the possibility of geoengineering, and the upcoming IPCC 5th Assessment Report is expected to include a section on climate engineering.

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A regular contributor to Yale Climate Connections since 2012, David Appell, Ph.D., is a freelance writer living in Salem, Oregon, specializing in the physical sciences, technology, and the environment. His...