Can geoengineering fix the climate? Hundreds of scientists say not so fast
by Oliver Milman  /  25 Dec 2022

“As global heating escalates, the US government has set out a plan to further study the controversial and seemingly sci-fi notion of deflecting the sun’s rays before they hit Earth. But a growing group of scientists denounces any steps towards what is known as solar geoengineering. The White House has set into motion a five-year outline for research into “climate interventions”.

Those include methods such as sending a phalanx of planes to spray reflective particles into the upper reaches of the atmosphere, in order to block incoming sunlight from adding to rising temperatures. The work is required by Congress. It is “not new research, but a report that highlights some of the key knowledge gaps and recommendations of priority topics for relevant research”, said a spokesperson for the White House’s office of science and technology policy, adding Joe Biden’s administration wants “effective and responsible CO2 removal” as well as deep cuts to greenhouse gas emissions.

Several American researchers, somewhat reluctantly, want to explore options to tinker with the climate system to help restrain runaway global heating, even as they acknowledge many of the knock-on risks aren’t fully known. “Until recently, I thought it was too risky, but slow progress on cutting emissions has increased motivation to understand techniques at the margins like solar geoengineering,” said Chris Field, who chaired a National Academies of Sciences report last year that recommended at least $100m being spent researching the issue.

“Illustration of stratospheric aerosol injection, marine cloud brightening, and cirrus cloud thinning, the three solar geoengineering interventions considered in the report.”

“I don’t think we should deploy it yet and there are still a ton of concerns, but we need to better understand it,” Field said. “Climate change is causing widespread impacts, it’s costing lives and wrecking economies. We are in a tough position; we are running out of time, so it’s important we know more.” Previous attempts at running experiments for what is known as solar radiation management (SRM) have faced staunch opposition.  Last year, an exploratory flight in Sweden of a high-altitude SRM balloon, led by Harvard University researchers, was halted after objections by environmentalists and Indigenous leaders.

But at least one US startup is now hoping to leap ahead with solar geoengineering. Make Sunsets, backed by two venture capital funds, launched in October. It claims to have already run two internal test flights for its plan to inject sulphur via balloons into the stratosphere, more than 20km above the Earth’s surface. The venture, named after the deep red sunsets that would occur if particles were seeded into the stratosphere, says its “shiny clouds” will “prevent catastrophic global warming” and help save millions of lives. “Any human-caused release of carbon dioxide is geoengineering,” it argues on its website, which asks people to buy “cooling credits” to fund its work. “We screwed up the atmosphere, and now we have a moral obligation to fix things!”

“Diagram showing three potential solar geoengineering methods”

Edward Parson, an expert in environmental law at University of California, Los Angeles, says Make Sunsets’ claims that it could return the world to its pre-industrial temperature for just $50bn a year are “absurd”. He explains that most researchers are wary of deploying what they consider to be a desperate, last-ditch option. But Parson says the risks in researching solar geoengineering have been overblown and that the US “is probably the bold leader on this. It would be a big step forward if we have a research program. In my opinion, the probability that a nation makes a serious effort on solar geoengineering over the next 30 years is about 90%,” he adds.

“As impacts get much worse and if mitigation doesn’t massively increase, I judge it quite likely that some major nation considers its citizens are suffering climate harms that are intolerable.” This prospect horrifies opponents of solar geoengineering. An open letter signed by more than 380 scientists demands a global non-use agreement for SRM; it also says that growing calls for research in this area are a “cause for alarm”, due to an unknown set of ramifications that will have varying consequences in different parts of the world and could scramble “weather patterns, agriculture and the provision of basic needs of food and water”.

Frank Biermann, an expert in global governance at Utrecht University, said he’s also disturbed that solar geoengineering will create a sort of moral hazard where governments ease off efforts to cut emissions and fossil fuel companies use it as cover to continue business as usual. Planet-heating emissions are expected to hit a record high this year, even though they must halve this decade if the world is to avoid dangerous levels of global heating. “I would say the majority of scientists believe this is a crazy idea for a variety of reasons,” said Biermann, who thinks the US is an outlier because of its own large per-capita emissions and inconsistent adherence to global agreements.

“Soon, everyone who is dependent on coal, oil and gas will jump on the solar engineering bandwagon and say, ‘we can continue for 40 years with fossil fuels’ now. This debate threatens to derail current climate policies. It’s a huge risk.” Biermann likens research on blocking sunlight to the satirical movie Don’t Look Up, in which researchers who warn of a catastrophic incoming meteoroid are sidelined in favor of an outlandish plan to deal with it. “The only way to find out whether this works is to do it to the whole planet for several years,” he said. “I mean will 8 billion people sit there in our living rooms having our last meal waiting and hoping that elite western universities got it right, that the Americans will not mess it up?”

There isn’t any international governance around solar geoengineering for now. Critics fret that unilateral action to alter the climate could spark conflict if one part of the world benefits, while another suffers knock-on droughts or floods. Also, the addition of aerosols would have to be continuous to maintain the cooling – any disruption, either intentional or otherwise, would cause a sort of “termination shock”, where bottled up warming would be unleashed in a disastrously rapid jolt.

“Termination shock terrifies me,” said Lili Fuhr, a climate and energy expert at the Center for International Environmental Law. “This is just a gigantic gamble with the systems that sustain life on Earth. It could be weaponized, it could be misused – imagine if, say, India and Pakistan disagreed over one of them doing this. “We need to do more than just emissions cuts and I wish we had a magical fix to this, but this doesn’t turn bad ideas into good ones,” Fuhr adds.

The idea of recalibrating the world’s climate to deal with heat-trapping emissions isn’t new. A group of scientific advisers to Lyndon Johnson cautioned the US president about global heating in 1965, musing that “deliberately bringing about countervailing climatic changes therefore need to be thoroughly explored”. Calls for intervention have grown in recent years as countries continue to dawdle over emissions cuts and as an internationally agreed limit of 1.5C of global heating over pre-industrial times looms into view. There are several types of proposed geoengineering, such as pumping a mist of salt water into clouds to make them more reflective of sunlight, or to place ice particles in high-altitude clouds to stop them trapping so much of the heat that bounces off Earth.

The most high-profile method, though, is firing a reflective substance such as sulphur or chalk dust from nozzles into the stratosphere, where the particles would then circulate around the world and start deflecting the sun’s rays. David Keith, professor of applied physics and of public policy at Harvard, estimates that around 2m tons of sulphur a year, injected via a fleet of about 100 high-flying aircraft, would cool the planet by around 1C, around the amount it has heated up since the Industrial Revolution. All of this would cost several billion dollars a yearaccording to an estimate, and provide a relatively quick drop in temperatures. Keith argues it is more compelling than various carbon capture technologies that can take a long time and involve complex, expensive infrastructure. “Pretending that climate change can be solved with emissions cuts alone is a dangerous fantasy,” Keith has stated.

The basic physics of doing this is well understood, Parson said, likening it to the huge eruption of Mount Pinatubo in the Philippines in 1991, an event that expelled nearly 20m tons of sulphur dioxide into the stratosphere and caused global temperatures to drop temporarily by about 0.5C. “Most people didn’t notice that and there have been studies since that give us confidence it can be done,” said Parson. “We don’t know how it should be done, yet, and the environmental aspects and the governance remain concerns. It would be reckless to just start deploying this now but we have lost so many easy paths to limit the harms of climate change that we only face worse options.”

Spraying sulphur into the skylight of the Earth could deplete the ozone layer, some have suggested, and perhaps make the sky a milky white color. Other effects on regional weather are more uncertain, to the extent one recent novel based on the topic, The Ministry for the Future by Kim Stanley Robinson, depicted India embarking upon solar geoengineering to save itself from deadly heatwaves while another, Termination Shock by Neal Stephenson, conversely had India sabotaging a sulphur deployment system in Texas because it interfered with its monsoon.

The debate over how much we should meddle with the climate is likely to intensify as the fallout from global heating worsens. For now, opponents won’t back down. To Biermann, solar geoengineering should be considered by governments as being akin to landmines or biological weapons and blacklisted internationally. “This is just another one on this list,” he said. “People talk about the freedom of research, but you don’t have the freedom to sit in your back yard and develop a chemical bomb.”

“This alarmingly simple hack could let anyone tinker with the climate”

This alarmingly simple hack could let anyone tinker with the climate
by James Temple / February 13, 2019

“The scenario would go something like this. It’s the year 2051. A decade of drought, crop failure, and famine has killed millions across East Africa, sparking violent clashes over food and water. Similar scenes of death and devastation are playing out in other parts of the globe. In response, an environmental group, or maybe a humanitarian one, or perhaps just some individual with a huge social-media following, calls for a radical response: every citizen should launch high-altitude balloons into the sky, each carrying a small payload of particles that could reflect heat back into space.

“Make Sunsets claims it released balloons full of sulfur particles into the atmosphere”

This kind of distributed, DIY geoengineering scheme appears technically feasible, which raises troubling questions about the ability to regulate such technologies, according to a white paper published on the website of the Harvard Kennedy School’s Belfer Center late last year. It notes that hobbyist kits for unmanned high-altitude balloons can already be purchased for as little as $25, and imagines that such a campaign could be coordinated using social media, blockchain, and crowdfunding sites.

Adapting balloons into geoengineering devices may simply require mixing helium with a few kilograms of sulfur dioxide, a compound that in the stratosphere is converted into sulfuric acid, which in turn casts away heat. Pressure will build inside each balloon as it ascends, until it bursts somewhere above 20 kilometers (12 miles), scattering its contents into the atmosphere. Researchers have imagined other rogue geoengineering scenarios, including nations launching efforts unilaterally, which some believe could incite a war.

Given the relatively low cost and simple technology involved, even wealthy individuals could potentially go it alone, a possibility that David Victor, co-director of the Laboratory on International Law and Regulation at the University of California at San Diego, dubbed the “Greenfinger” scenario. In fact, one California businessman sparked international controversy in 2012 by dumping iron into the ocean, in an effort to stimulate the growth of carbon dioxide–gobbling phytoplankton.

The new paper essentially adds another category of unsanctioned scenario to fret over, and one suggesting that the technology could even be harder to regulate than previously imagined. “Given the globalization of communication and commerce, as well as the small scale of each act, highly decentralized solar geoengineering would be difficult to eradicate altogether,” argue the authors, Jesse Reynolds, an environmental law and policy fellow at the University of California, Los Angeles, and Gernot Wagner, co-director of Harvard’s Solar Geoengineering Research Program (who is moving to New York University this fall).

A growing number of researchers and officials contend that we should explore geoengineering as a way to reduce the impact of climate change, given the rising dangers and stunted efforts to cut emissions. In October, the US National Academies announced plans to lay out a formal research agenda and develop standards governing research practices. But the question of how the technology should be regulated is highly fraught. What body should oversee its deployment? What level of consensus is required for use of a technology that could alter the climate of every nation but affect different areas very differently? And what’s the appropriate average global temperature target?

A DIY scheme makes all this far more complicated. For starters, the environmental implications of geoengineering vary according to what types of particles are used, how fast they are released, and in what amounts. All that will be much harder to control or modulate if it’s being carried out by thousands of individuals. Such an effort couldn’t be carefully dialed up or down in response to how the climate system reacts—which, for all the modeling that’s been done, can’t be known with certainty until geoengineering is actually deployed. It may also leave the world more open to what’s known as termination shock: if people suddenly stopped sending out those balloons, whether because it was outlawed or they simply moved on to other things, whatever climate warming happened while the effort was under way would manifest all at once.

UC San Diego’s Victor compares the prospect of DIY geoengineering to the challenges of preventing gun violence. “Anything that democratizes the technologies of geoengineering probably makes the governance problem harder,” he said in an e-mail. “Restraint is harder when the numbers of actors is much larger and when the technology is easier to obtain for actors who may be particularly prone to use the technology irresponsibly.” Still, he’s not convinced that the balloon scenario is all that feasible, or at least all that likely. Victor believes that new laws in North America and Europe would be enough to prevent most people in those areas from participating in such an effort—and that state-backed geoengineering efforts are the more realistic risk in other parts of the world. Reynolds and Wagner themselves recognize that the plot they’ve laid out is unlikely, even if it’s technically feasible.

The paper notes that a hundred million balloons would have to successfully release around 10 kilograms of sulfur dioxide to lower global temperatures by around 0.1 ˚C in the following year. That’s a lot of balloons for a fairly small temperature difference, and any such efforts would have to be continually repeated. But the authors add that the effort could simply amount to a kind of protest against inaction, even if it’s not large enough to really move temperatures. Reynolds says much of the governance debate over geoengineering to date has focused on regulating state-sponsored deployment scenarios or research efforts. The point of the paper was to begin exploring prospects that we’re not expecting. “We need to keep our thinking open to multiple possibilities,” he says.

Whether the balloon concept is feasible or not, the basic point remains that geoengineering, in any scenario, poses incredibly vexing governance questions. Some argue that these challenges and the environmental unknowns mean the world can never safely conduct geoengineering, and we should all stop talking about it and giving anyone crazy ideas. But geoengineering is so cheap and simple, and climate change is so perilous, that it probably will be done in some form and at some scale.

And we don’t yet know exactly how it will play out within an incredibly complex climate system. Given those risks—and the real chance that we may one day need it—it’s far preferable for researchers and policy experts to explore every conceivable scenario, determine the safest methods, strive for workable if imperfect regulatory frameworks, and communicate clearly about the potential benefits and inevitable side effects.”

Giant pipe and balloon to pump water into the sky in climate experiment
by John Vidal / 31 August 2011

“It sounds barmy, audacious or sci-fi: a tethered balloon the size of Wembley stadium suspended 20km above Earth, linked to the ground by a giant garden hose pumping hundreds of tonnes of minute chemical particles a day into the thin stratospheric air to reflect sunlight and cool the planet. But a team of British academics will next month formally announce the first step towards creating an artificial volcano by going ahead with the world’s first major “geo-engineering” field-test in the next few months.

The ultimate aim is to mimic the cooling effect that volcanoes have when they inject particles into the stratosphere that bounce some of the Sun’s energy back into space, so preventing it from warming the Earth and mitigating the effects of man-made climate change. Before the full-sized system can be deployed, the research team will test a scaled-down version of the balloon-and-hose design. Backed by a £1.6m government grant, the team will send a balloon to a height of 1km over an undisclosed location. It will pump nothing more than water into the air, but it will allow climate scientists and engineers to gauge the engineering feasibility of the plan. Ultimately, they aim to test the impact of sulphates and other aerosol particles if they are sprayed directly into the stratosphere.

If the technical problems posed by controlling a massive balloon at more than twice the cruising height of a commercial airliner are resolved, then the team from Cambridge, Oxford, Reading and Bristol universities expect to move to full-scale solar radiation tests. The principal investigator, Matthew Watson, a former UK government scientific adviser on emergencies and now a Bristol University lecturer, says the experiment is inspired by volcanoes and the way they can affect the climate after eruptions. “We will test pure water only, in sufficient quantity to test the engineering. Much more research is required,” he said, in answer the question of what effect a planetary-scale deployment of the technology could have.

Other leaders of the government-funded Stratospheric particle injection for climate engineering (Spice) project have investigated using missiles, planes, tall chimneys and other ways to send thousands of tonnes of particles into the air but have concluded that a simple balloon and hosepipe system is the cheapest. The research is paid for by the government-funded Engineering and Physical Sciences Research Council. “The whole weight of this thing is going to be a few hundred tonnes. That’s the weight of several double-decker buses. So imagine how big a helium balloon do you need to hold several double-decker buses – a big balloon. We’re looking at a balloon which is possibly 100-200m in diameter. It’s about the same size as Wembley stadium,” said the Oxford engineering lecturer Hugh Hunt in an interview earlier this year. “This hose would be just like a garden hose, 20km long and we pump stuff up the pipe. The nice thing about it is that we can really have a knob, if you like, which we can control to adjust the rate at which we inject these particles.”

While the October experiment is expected to have no impact on the atmosphere, it could also be used to try out “low-level cloud whitening”, a geo-engineering proposal backed financially by Microsoft chairman and philanthropist Bill Gates. In this case, fine sea salt crystals would be pumped up and sprayed into the air to increase the number of droplets and the reflectivity in clouds. Together, many droplets are expected to diffuse sunlight and make a cloud whiter. However, environment groups in Britain and the US said the government’s experiment was a dangerous precedent for a full-scale deployment that could affect rainfall and food supplies. Even if the approach successfully cools the planet by bouncing some of the Sun’s energy back into space, it would do nothing for the build up of CO2 in the atmosphere, which leads to increased ocean acidity.

“What is being floated is not only a hose but the whole idea of geo-engineering the planet. This is a huge waste of time and money and shows the UK government’s disregard for UN processes. It is the first step in readying the hardware to inject particles into the stratosphere. It has no other purpose and it should not be allowed to go ahead,” said Pat Mooney, chair of ETC Group in Canada, an NGO that supports socially responsible development of technology. Mike Childs, head of science, policy and research at Friends of the Earth UK, said: “We are going to have to look at new technologies which could suck CO2 out of the air. But we don’t need to do is invest in harebrained schemes to reflect sunlight into space when we have no idea at all what impact this may have on weather systems around the globe.”

But the principle of large-scale geoengineering has been backed strongly by Sir Martin Rees, the former president of Royal Society, which in 2009 concluded in a report that it may be necessary to have a “plan B” if governments could not reduce emissions. “Nothing should divert us from the main priority of reducing global greenhouse gas emissions. But if such reductions achieve too little, too late, there will surely be pressure to consider a ‘plan B’ – to seek ways to counteract the climatic effects of greenhouse gas emissions by ‘geoengineering’,” said Rees. Members of the British public who were consulted by researchers in advance of the Spice experiment were broadly sceptical. “Overall almost all of our participants were willing to entertain the notion that the test-bed as an engineering test – a research opportunity – should be pursued. Equally, very few were fully comfortable with the notion of stratospheric aerosols as a response to climate change,” the Cardiff University-based researchers concluded.

Hacking the planet – potential geo-engineering solutions

Ocean nourishment
Billions of iron filings are deposited in the ocean to stimulate a phytoplankton bloom. The aim is to enhance biological productivity to remove carbon dioxide from the atmosphere. Many experiments have been conducted, including fertilisation of 900 square kilometers (350 sq miles) of the Atlantic. Results so far are disappointing.

Space mirrors
Giant “mirrors”, made of wire mesh, could be sent into in orbit to deflect sunlight back into space. But the scale needed, the expense and the potential unintended consequences are so great that it is widely considered unrealistic. In the same league as the idea to mine the moon to create a shielding cloud of dust.

Cloud whitening
The idea is to increase the water content in low clouds by spraying sea water at them. This makes them reflect more sunlight. It would be pretty harmless, and cheap but would have to be done on an immense scale to have any global effect. Backed by Bill Gates.

Artificial trees
Proposed by climate scientist Wallace Broecker who imagines 60m artificial “trees” dotted around the world, “scrubbing” the air by capturing CO2 in a filter and then storing it underground. The trees could remove more carbon dioxide than an equivalent-sized real tree.

Albedo changes
Painting roofs and roads white, covering deserts in reflective plastic sheeting, dropping pale-coloured litter into the ocean and genetically engineering crops to be paler have all been proposed to reflect sunlight back into space.

Carbon capture and storage (CCS)
Carbon dioxide is collected from coal or other fossil fuel power plants and is then pumped underground. Works in principle but it is expensive and increases the fuel needs of a coal-fired plant by 25%-40%. More than 40 plants have been built with many others planned.

“This article was amended to remove a reference to the Royal Society”



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