Can we engineer our way out of the climate crisis?

While governments are struggling to limit emissions of CO2 and other greenhouse gases, a number of scientists are more and more convinced that we cannot avoid deliberately manipulating the climate. But some concepts of climate engineering are quite adventurous and possibly as dangerous as climate change itself.

By Michael Förtsch

To say that the situation is serious would be an understatement. Climate change and global warming are becoming more and more visible. A United Nations report, published in November 2019, predicts that unless there is a major climate protection effort, the Earth’s average temperature will rise by 3.4 to 3.9 degrees by the end of the century. This would trigger widespread droughts, mass extinctions of animal species, water shortages throughout nations, and thus the flight of hundreds of millions of people. The number of hot days in Germany has already increased and at the same time the number of deaths due to heat stress in the sick, the elderly and children, as was shown by a study by the Federal Ministry of the Environment. Extreme weather conditions, storm surges and low water levels are also increasing today.

But despite the visible consequences, despite international protests and appeals from activists such as Greta Thunberg and renowned climate scientists, the efforts of the states are rather moderate. Too little, preliminary studies have shown, is being done to curb emissions of millions of tonnes of CO2 and other greenhouse gases such as methane. Instead of a reduction in emissions, a record high was reached in 2018. As a result, a tool that has been considered too extreme and invasive to curb climate change increasingly seems to be thinkable. At least more and more scientists and even the Intergovernmental Panel on Climate Change IPPC believe that its use may be necessary. We are talking about geo- and climate-engineering, the deliberate manipulation of the climate.

Should we simulate a volcanic eruption?

The year 1816 was not a good year. It was the year without a summer, as it is still called today. Because it was one of the coldest years in centuries. In the middle of the summer there was frost, harsh rainfall, hail and flooding. This led to crop failures, famines and thousands of deaths in Europe and North America. For a century, it was a mystery what had caused this bizarre year of misery. In 1920, the climatologist William Jackson Humphreys concluded that the Tambora volcano was behind it. Its eruption in April 1815 had hurled more than 150 cubic kilometers of dust, ash and sulfur into the atmosphere. They enveloped the globe like a veil that robbed the sunlight of its power: a volcanic winter.

Today’s climate scientists believe that the effects of such a volcanic eruption can be artificially re-energised. Only last year, researchers at Harvard University started a study to test whether and how effective this could work. In a first test, a balloon brought up small amounts of calcium carbonate particles. The researchers then observe how the particles are distributed and what effects they might have on solar radiation. According to David Keith, the project’s director, these attempts were to „explore whether the albedo, the reflectivity, of our planet can be increased and thus the solar radiation that reaches the Earth’s surface can be controlled.“

The eruption of Mount Cleveland was far less extreme than that of Tambora but also hurled considerable amounts of ash into the atmosphere.

Of course, the researchers do not want to cause frost and famine, that occurred when Tambora erupted, but rather to lower the average temperature of the earth or even individual regions. The technology of this Solar Radiation Management „does not make it unnecessary to reduce CO2 in the atmosphere,“ says Keith. „But it could mitigate the immediate consequences of climate change. We can intervene and quickly achieve temporary effects.“ For example, heat periods could be combated that would otherwise cause considerable damage to humans, plants, animals, the ecosystem, but also to the economy. The technology could also be used on a large scale to artificially pause climate change, while climate protection programmes are implemented around the world.

According to a calculation by Keith and his colleagues, the estimated global warming could be reduced by up to half. Other researchers, [such as Wake Smith of Yale University, are not only convinced that this is credible and feasible, but also comparatively cheap. A global solar radiation management program only needs 60,000 flights a year with 100 specially adapted aircraft. That would cost about 2.5 billion U.S. dollars per year.

Giant mirrors and mega-lenses in space

The idea from Harvard – that is, artificially reducing solar radiation to Earth – is not new. For decades, scientists have been working on various ways to manipulate both the regional weather and the climate. Above all, it is about the targeted reflection and blocking of sunlight, as this would have an immediate effect. Ideas include almost pragmatically simple means, such as equipping houses with white roofs or so-called Cool Roofs, which, as a study by the University of Southern California states, „absorb less sunlight than traditional roofs, reduce heating and the heat emitted into the atmosphere.“ The large-scale cultivation of plants with white flowers and spraying of artificial snow should have a very similar effect.

More extreme agents, however, which have been debated as options, would be to span and spray desert surfaces with reflective or white films, liquid films or confetti-like particles. There are also considerations of releasing several hundred to tens of thousands of balloons with silver coatings in cities and forests, depending on the area. As a result, the temperature can be lowered by two to three degrees Celsius, at least regionally. If these methods were actually applied on a large scale, a global effect could be achieved and the temperature of the world could be lowered. At least that is what environmental and material researcher Alvia Gaskill argued ten years ago.

Scientists at oil giant Exxon , now ExxonMobil, have also been researching measures to manipulate the climate. As early as the 1970s, the company began to accumulate evidence-based studies on the dangers of climate change – even if the company publicly claims otherwise. The Exxon researchers calculated that if 55,000 mirrors with a total area of 100 square kilometers were transported into orbit, about one to maybe even two percent of the sun’s irradiation could be blocked. An idea that also didn’t seem ludicrous to Edward Teller, the father of the hydrogen bomb..

James Early, a Harvard researcher, considered it realistic in 1989 that a 2,000-kilometer lens could be positioned between the sun and the earth. This Fresnel or step lens would be positioned at the so-called Lagrange point 1 and could thus shone the light that directly hits the earth like an inverted magnifying glass and thereby weaken it. This is an idea with which Early was not alone. The physicist and author Gregory Benford also had such a consideration, but believed that a 1,000 kilometer broad and only a few millimeters thick lens would be enough to reduce the sun’s irradiation by 0.5 to 1 percent.

Other ideas to weaken the sun include ships sailing around the oceans as gigantic steam engines to blow artificial clouds into the sky covering the earth’s surface, and especially the melting poles. This sounds absurd, but as initial tests had shown, it could work. It would also be possible to extract salt particles from the seas and blow them into the clouds in order to make them brighter and thus more reflective. Another consideration is to darken the sky by mixing airplane fuels with sooty aerosols. Even covering the ocean with floating plastic and aluminum chips or tons of plastic balls, or blowing moon or asteroid dust between earth and sun were possibilities.

Sucking CO2 from the air

Of course, it’s not just reducing the sunlight what could manipulate the climate. There is also the substance that has caused the climate to change: CO2, carbon dioxide. Instead of just reducing its emissions, some scientists and activists are calling for actively pulling it out of the atmosphere: a concept called Carbon Dioxide Removal. One idea is to enliven the sea by pumping ton of iron sulphate and nutrients into it. The naval biologist Callum Roberts of York University, on the other hand, calls for making the ocean less acidic by using chemicals such as olivine and calcium carbonate.

The goal? Both methods are intended to stimulate the growth of algae and corals that absorb and store CO2. The carbon absorbed would sink to the seabed – and remain there for the long term – if the plants die later. At least that is the simple and at first plausible consideration. Studies carried out over the past few years, however, have produced different results. It turned out that the fertilization of the oceans is likely to succeed in principle – but not whether it would be as effective as hoped. Ultimately, this depends on which organisms benefit and grow the most as a result.

Nevertheless, some influential scientists welcome the approach – partly because it would be feasible immediately. The necessary fertilisers and chemicals are mass-produced, as are ships to distribute them. „Let’s look at the shallow seas in coastal areas, many of which were once rich in seaweed and algae,“ says David King, the former adviser to the British government on climate change. Re-greening these areas is „a relatively simple matter“ and can be done „in a few weeks“.

Several start-ups are now pursuing an even more active approach to CO2 reduction. For example, the Swiss company Climeworks is working on a combination of air filters and blowers, which are assembled as walls to extract the CO2 from the air and pump it underground, where it reacts with basalt rock and even petrifies. The first plants in Hinwil, Switzerland, have been running since 2017, where they are expected to collect up to 900 tons of carbon dioxide per year. Iceland is now also fitted with a filter system, which is operated jointly with the University of Iceland and the energy supplier Reykjavik Energy.

Global Thermostat from New York, on the other hand, wants to retrofit dirty power plants and plants with large tube absorbers so that they can not only no longer emit CO2, but also capture additional CO2 from the environment. Arizona State University recently announced that it will convert a CO2 absorber developed by researcher Klaus Lackner, which is a kind of mechanical tree more reminiscent of a vertical folding roof, into a test series. Twelve of these trees could capture just over a tonne of CO2 per day.

A more exotic option to get CO2 out of the atmosphere would be to accelerate the weathering of stone, especially lime and other silicates. In this decomposition process, they bind small amounts of CO2. In practice, this would mean removing rocks and mountains on an industrial scale, rasping them into small pieces and distributing the boulders. However, entire mountain landscapes would have to be leveled in order to do so effectively. This would not be particularly economical and landscape-friendly.

Do we have a choice?

The above methods are just some of the ideas for Climate Engineering. There are many others. Apart from fertilizing the seas, none of them is yet ready for use on a large scale. But certainly, they all share a problem: the consequences the plans might have are difficult to estimate. Harvard researcher David Keith, who wants to bring reflective particles into the atmosphere, said in a lecture that his method will have „many puzzles in detail and some bad side effects.“ The climate is such a complex system that even the smallest interventions could have unexpected and devastating consequences.

Flooding the sky with artificial clouds or particles could turn the weather of entire countries upside down, causing droughts, hurricanes, or storm surges. This, in turn, could trigger international conflicts, lawsuits, and wars if individual nations, or perhaps even companies, do something unilateraly. It would never be certain whether climate engineering or climate change was the trigger. Whether and how climate engineering would currently be permitted under international law is equally uncertain in the opinion of the Federal Ministry of Education and Research of Germany.

Nevertheless, the number of experts who believe that the methods of climate engineering should be researched vigorously and considered as a possible tool is increasing. The simple reason for this is that even if greenhouse gas emissions are drastically reduced, it may not be enough to prevent a climate catastrophe. At least not one that would seriously affect all life on the planet.

Teaser image: Getty Images / coffeekai