Monday , March 8 2021

The first solar dimming experiment will test a way to cool the Earth

Zhen Dai, Frank Keutsch and David Keith

Frank Keutsch, Zhen Dai and David Keith (from right to left) at Keutsch's Harvard University lab.Credit for Kayana Szymczak Nature

Zhen Dai holds a small glass tube covered with a white powder: calcium carbonate is a compound that is used everywhere, from paper and cement to toothpaste and cake mixtures. Spray a tablet into water and a gaseous antacid is formed that calms the stomach. The question of Dai & colleagues, a doctoral candidate at Harvard University in Cambridge, Massachusetts, is whether this harmless matter can help mankind get rid of the greatest indigestion: global warming caused by greenhouse gas pollution.

This idea is simple: spray a piece of particle into the stratosphere and cool the planet by reflecting some rays of the Sun back into space. Scientists have already witnessed the principle of action. When Pinatubo Mountain erupted in the Philippines in 1991, an estimated 20 million tonnes of sulfur dioxide was injected into the stratosphere. It was the atmosphere layer 10 to 50 kilometers from the Earth's surface. The explosion caused a particles of sulphate, which had cooled down to about 0.5 ° C, causing haze. For approximately 18 months, the average temperature of the Earth returned to its state before the steam engine arrived.

The idea that people can reverse the world thermostat with similar, artificial means dates back a few decades. It follows a larger class of planet-refrigeration programs, known as geoengineering, which have long-lasting controversy and, in some cases, fear.

Researchers have severely limited their work on such tactics with computer models. Among the concerns is that the darkening of the Sun can degrade some parts of the world, for example, from sunlight, and can repulse or at least become disadvantageous by changing rain patterns.

However, while emissions continue to increase and climate projections are still poor, conversations about geoengineering research are beginning to be more controversial among scientists, policy makers and some environmentalists. Because many researchers have come to an alarming conclusion that the only way to prevent the serious effects of global warming is to absorb large amounts of carbon dioxide from the atmosphere or to artificially cool the planet. Or maybe more likely.

If everything goes as planned, the Harvard team will be the first to move solar geoengineering from the lab to the stratosphere with a project called the Stratospheric Controlled Perturbation Test (SCoPEx). The first phase – a $ 3 million test that included two flights of a steerable balloon 20 kilometers up the southwestern United States – was able to start as early as the first half of 2019. When placed, the experiment would reveal small calcium carbonate plumes, approximately 100 grams each, equal to the amount in the antacid bottle found on a roughly average shelf. The balloon will rotate to observe how the particles are dispersed.

The test itself is extremely modest. Dai, who has been studying for the last four years, did not emphasize the concerns about such research, which included establishing a desktop device to simulate and measure the chemical reactions in the stratosphere before the experiment. Or I'm reading a chemical, “he says. "It's not like a nuclear bomb."

However, the experiment will be the first to fly under the banner of solar geoengineering. And including some environmental groups, these efforts are under intense scrutiny that addressing the only permanent solution to climate change is a dangerous distraction: reducing greenhouse gas emissions. The scientific output of SCoPEx is not really important, says Jim Thomas, an executive director of ETC Group's environmental advocate in Val-David, Montreal, Canada, opposes geoengineering: P is try. it is a science experiment to change social norms and pass a line. "

Being aware of this attention, the team is moving slowly and trying to establish an open supervision for the experiment as an external advisory committee to review the project. Some say that such a framework, which can pave the way for future experiments, is more important than the results of this single test. Le The SCoPEx is the first exit point of the door and triggers an important talk about how independent guidance, advice and supervision should be, bağımsız says Peter Frumhoff, chief climate scientist at the Cambridge University of Cambridge, and the chairman of the advisory committee. member of an independent panel. ”It's more important to do it right than it's done quickly.“

Join the team

In many ways the stratosphere is the ideal place to make the atmosphere more reflective. Small particles injected there can spread all over the world and remain open for two years or more. If they are strategically and regularly placed in both hemispheres, they can form a relatively uniform cover to protect the entire planet (see de Global intervention Her). The process does not have to be extremely expensive; In a report published last month, the Intergovernmental Panel on Climate Change suggested that the fleet of a high-flying aircraft would be able to accumulate enough sulfur to balance heating from about $ 1 billion to about $ 10

Paul Jackman /Nature

Most of the solar geoengineering studies have focused on the sulfur dioxide, the same substance released by Pinatubo Mountain. But sulfur may not be the best candidate. In addition to cooling the planet, aerosols produced in this explosion increased the speed at which chlorofluorocarbons consumed the ozone layer, which protects the planet from harmful ultraviolet radiation. Sulphate aerosols are also sufficient to warm up by the sun, potentially influence the moisture movement and even change the jet flow. Olan There are all these downstream influences that we don't fully understand, Frank says Frank Keutsch, an atmospheric chemist who is one of Harvard and SCoPEx's top researchers.

The first stratospheric experiments of the SCoPEx team will focus on calcium carbonate, which is expected to have less heat absorption than sulfates and less effect on ozone. However, textbook answers – and even the Daitıs desktop device – cannot take the entire picture. ”We don't really know what to do because it doesn't exist in the stratosphere, Ke says Keutsch. ”It builds a red flag.“

SCoPEx aims to collect real world data to solve it. The experiment began as a partnership between the experimental physicist David Keith and Harvard's atmospheric chemist James Anderson. Keith has been researching various geoengineering options for over 25 years. In 2009, at the University of Calgary in Canada, he founded Carbon Engineering at Squamish, a company that has been working to commercialize technology to spread carbon dioxide to the atmosphere. After attending Harvard, Keith used research funds from the Bill & Melinda Gates Foundation in Washington, DC to begin planning the experiment.

Later, Keutsch is not a climate scientist and is the most reluctant geologist. But he worries about where humanity has gone and what it means for the future of his children. When Keith talked about the idea of ​​SCoPEx at a conference after he started in Harvard in 2015, he said the initial reaction was & totally insane;. Then it's time to be engaged. Um What can I do to myself, an atmospheric chemist? Bir I asked. He joined forces with Keith and Anderson and since then has been a pioneer in experimental work.

A look at the sky

Already SCoPEx has moved further than the previous solar power generator works. The United Kingdom Stratospheric Particle Injection, intended to spray 1 km of water into the atmosphere, was partially canceled in 2012 because scientists filed a patent application on a device that could ultimately affect every person on the planet. (Keith says there will be no patent in any technology involved in the SCoPEx project).

Environmental chamber for testing instruments used in SCoPEx field mission

SCoPEx is an environmental chamber for testing instruments used in the field mission.Credit for Kayana Szymczak Nature

Although SCoPEx is the first solar generator test to fly, Keith says that other projects that didn't mark them this way before provided useful data. For example, in 2011, the East Pacific Emission Aerosol Cloud Experiment pumped smoke into the lower atmosphere to mimic pollution from ships, capturing more water vapor and causing clouds to shine. The test was used to study the impact on sea clouds, but the results had a direct impact on geoengineering science: the brighter clouds created a cooling effect 50 times greater than the warming effect of carbon emissions from the ship's researchers.2nd.

Keith says the Harvard team occasionally did not face protests or any direct opposition – with occasional conspiracy theorist. The difficulty that researchers face is that science-finance institutions fear that those who invest in geoengineering will lead to protests by environmentalists.

In order to help advance the field, Keith set a $ 20 million target in 2016 to support not only experimental work but also a formal research program that covers modeling, governance and ethics. So far, the Gates Foundation has earned over $ 12 million to date from other charities; the pot provides funding to dozens of people, largely on a part-time basis.

Keith and Keutsch want an external advisory committee to review SCoPEx before they fly. The committee to be elected will report to Harvard engineering dean and research assistant. U We see this as part of a process to create a wider support to investigate, Ke says Keith.

Keutsch is looking forward to having the guidance of an external group and hopes that such tests can clarify how it should continue. Iyor This is a far more politically challenging experiment than I thought, “he says. “I was a little naive“

SCoPEx also faces technical challenges. It has to spray particles of the correct size: the team calculates that those with a diameter of about 0.5 micrometers should be able to well distribute and reflect sunlight. The balloon can also reverse its course in the fine air, so it can pass through its wake. Assuming the team is able to find the calcium carbonate feather – and there is no guarantee they can do – SCoPEx needs tools to analyze the particles and, if possible, transports the samples back to Earth.

& This is going to be a hard experiment and it might not work, Colorado says David Fahey, an atmospheric scientist at the National Oceanic and Atmospheric Administration in Boulder, Colorado. Hopefully, Faheyçes team provided SCoPEx with a lightweight instrument that can reliably measure the size and number of particles placed on the market. The balloon will also be equipped with a laser device that can monitor hairs remotely. Other equipment that can collect information about the moisture and ozone levels in the stratosphere can also fly on the balloon.


Keutsch and Keith are still working on some technical details. Plans with a balloon company have fallen, they are now working for a second. And an independent engineer team in California is working on options for the spray gun. To simplify work, the SCoPEx group plans to fly the balloon in spring or autumn, making the stratospheric winds change direction and for a short period of time to make it easier to follow the feathers.

For all these reasons, Keutsch qualifies the first flight as an engineering test, mainly aimed at showing that everything is working properly. The tool is ready to spray the calcium carbonate particles, but may use saline to test the sprayer if the consultation committee has targets.

Keith thinks that sulphate aerosols may be the best option for solar generations. Due to the continued efforts to restore the ozone layer through the reduction of the ozone layer, the possibility of sulphate, which increases the ozone layer, should be less concerned in the future. However, its main hope is to create an experimental program where scientists can explore different aspects of solar engineering.

There are a lot of extraordinary questions. Some researchers have suggested that solar geoengineering can change the rainfall patterns and may even lead to more drought in some regions. Others may not warn – that one of the possible benefits of solar generation – preserves crop yields from heat stress. In a study published in August, the researchers found corn (corn), soy, rice and wheat yields.3 After two volcanic eruptions, he fell in 1991 on Mount Pinatubo and El Chichón in Mexico in 1982, and stopped the sky. These discounts may be sufficient to cancel potential gains in the future.

Keith says that science has so far suggested that benefits can outweigh potential negative consequences, especially when compared to a world where warming is not controlled. The common disadvantage is that the protection of the sun does not affect emissions, so that greenhouse gas levels continue to increase and the ocean becomes more acidic. However, he suggests that solar generation can reduce the amount of carbon, including reducing the carbon dioxide in the atmosphere, encouraging forest growth, and reducing the need to cool the buildings. Keith et al. Found that in a recent unpublished analysis of precipitation and extreme temperatures using a high-resolution climate model, nearly all regions of the world could benefit from a moderate solar generator program. Or Despite all the concerns, we can't find any areas that are definitely worse, bu he says. Kadar If the solar power generator is as good as shown in these models, it would be crazy not to take it seriously. “

There is still widespread uncertainty about the state of science and the assumptions that exist in the models – including the idea that humanity can come together in order to establish, maintain and disassemble a well-designed geoengineering program when dealing with the underlying emission problem. Nevertheless, leading organizations, including the Royal Society of the United Kingdom and the US National Academy of Science, Engineering and Medical, urged further research. In October, academies launched a project to try to present a plan for such a program.

Some organizations are already trying to promote discussions between policy-makers and government officials on an international level. For example, the Solar Radiation Management Governance Initiative organizes workshops in the global south. Janos Pasztor, who has addressed climate issues in former UN secretary-general Ban Ki-moon, talks with top government officials around the world as head of Carnegie Climate Geoengineering Governance Initiative, a non-profit organization. New York. Dır Governments should participate in this discussion and understand these issues,. Says Pasztor. ”They must understand not only the risks but also the risks of understanding and not knowing.“

One concern is that governments someday panick over the consequences of global warming and rush through a random solar-geoengineering program. Costs may be a distinct possibility, given that many countries, and perhaps even a few individuals, are likely to be cheap enough. to go alone. These and other questions emerged earlier this month at the annual summit of the Montreal Protocol, which manages the chemicals that damage stratospheric ozone layer in Quito, Ecuador. Several countries have asked for a scientific assessment of the potential impacts of solar generation on the ozone layer and the stratosphere.

If the world is serious about geoengineering, Fahey says there are many complex experiments that researchers can do using satellites and high flying planes. But for now, he says that SCoPEx will be valuable – if it only promotes conversation. Imiz Not talking about geoengineering is the biggest mistake we can make right now. “

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