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All about space
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In 2021, the Earth took a dark step: the concentration of carbon dioxide (CO2) in the atmosphere reached 150% of its value in pre-industrial times, according to the UK Met Office. To avoid the worst effects of climate change, the world must reduce net carbon dioxide emissions to zero by 2050.
But even if we did achieve this target, it would not put the brakes on temperature rises sharply, as it takes time to see the effects of CO2 reductions on global temperatures; the negative impacts of global warming will continue for decades. But is there anything else we can do to reduce temperatures faster?
A Harvard University research group believes that a temporary reduction in global temperatures could be achieved by changing the composition of Earth’s upper atmosphere. The researchers hoped to test some of this technology – and the viability of their theory – this summer, in what they call the Stratospheric Controlled Disturbance Experiment (SCoPEx). Although work has been suspended, the team still hope that the experiment continues for the not-too-distant future.
Earth’s ultimate heat source is the sun, which bathes the day side of the planet in a constant stream of infrared radiation. About 30% of this is reflected back into space by the atmosphere, while the rest warms the planet during the day and is sent back into space at night. In the delicate balance that prevailed in pre-industrial times, the incoming heat was exactly compensated by the amount lost in space, ensuring that global average temperatures remained constant.
The problem today is that CO2 emissions upset this balance by absorbing some of the heat that should be sent back into space, trapping it inside the atmosphere. The more carbon dioxide there is in the atmosphere, the more the temperature rises. In the long term, humans must reduce the amount of carbon dioxide in the atmosphere to avoid the worst effects of climate change. But other processes can produce short-term reductions in global temperature.
Volcanic eruptions, for example, throw clouds of dust particles high into the stratosphere, an upper layer of the atmosphere, forming a protective shield that prevents some of the sun’s heat from reaching the surface of the earth. Earth. The 1991 eruption of Mount Pinatubo in the Philippines, for example, caused the average temperature in the northern hemisphere to drop by about 1 degree Fahrenheit (over half a degree Celsius) over the next 15 months. The SCoPEx team wants to take a page from such eruptions by injecting particles into the upper atmosphere in order to bring down temperatures.
The basic idea – called Stratospheric Aerosol Injection, or SAI – is simple. A high-flying plane or helium balloon would distribute batches of microscopic particles called aerosols into the stratosphere at altitudes of 12.4 miles (20 kilometers) or higher – much higher than planes usually fly. The aerosols would remain suspended in the air, too small to be visible as clouds from the ground but opaque enough to reflect a fraction of the sun’s energy back into space.
In the simulations, the ISC appears to be a viable concept. A2018 Report of the Intergovernmental Panel on Climate Change (IPCC) found that a fleet of high-flying planes could deposit enough aerosols to offset current levels of global warming. But the aerosols would need to be renewed every few years, and the method only tackles one of the symptoms of climate change rather than addressing its root cause, the Greenhouse effect. At best, it is a stopgap measure, countering rising temperatures as countries simultaneously reduce carbon dioxide levels.
So far, research on SAI has been theoretical, supplemented by a limited amount of real-world data from volcanic eruptions. SCoPEx wishes to perform real world measurements under carefully controlled conditions, allowing better calibration of computer models. “If we are to provide policy makers with useful information on whether this might work, we need to check our models,” said project principal investigator Frank Keutsch, of the Department of Chemistry and Chemical Biology at Harvard University, told the Boston Globe.
Volcanoes mainly release sulfur-based compounds. But these compounds not only cool the atmosphere, but also damage the protection of the Earth. ozone layer that protects us from harmful UV rays. The SCoPEx team is therefore focusing on a less harmful aerosol, calcium carbonate, in other words chalk dust, which the researchers hope will produce the desired cooling effect without damaging the ozone layer.
Proposed experience
The team wants to deploy a large helium balloon which would be similar to a standard weather balloon except that it would be equipped with propellers to allow the ground crew to maneuver it in a controlled manner. With help from the Swedish Space Corporation, scientists planned to launch the balloon near Kiruna, Sweden.
During its first flight, which is tentatively scheduled for next year, the balloon would drop nothing into the stratosphere. Instead, it would climb to an altitude of 12.4 miles, where the team would test the maneuver system and verify that all scientific instruments and communications were functioning properly.
If the test was successful, a second flight would achieve a controlled release of 2.2 to 4.4 pounds (1 to 2 kilograms) of calcium carbonate at the same altitude. The balloon would move steadily in a straight line during the release, so the aerosol particles would form a narrow plume about 1 km long. The balloon would then return through the plume, observing how the particles disperse over time and how well they reflect sunlight, according to the SCoPEx website.
As valuable as the SCoPEx test flight may be to our understanding of ISC, it is important to see the project in perspective. “The point is not to change the climate or even to see if you can reflect sunlight,” said one of the scientists on the project, David Keith, professor of applied physics at Harvard, previously said HowStuffWorks. “The goal is simply to improve our models of how aerosols form in the stratosphere.”
At least another decade of research will be needed before a large-scale aerosol release, Keith said. The release “could involve the injection of about 1.5 million tonnes [1.4 million metric tons] in the stratosphere per year, ”he said. “About a hundred planes would need to continuously carry payloads up to about 12 miles. [20 km] altitude.”
Controversy
The ISC remains very controversial, however. One concern is that humans created the climate crisis in the first place by pumping greenhouse gas in the atmosphere, so how can people be sure pumping aerosols will make things better? Although computer modeling suggests that IAD is safe, it is still possible that it has unforeseen side effects. It is possible that this will disrupt weather conditions, damage crops by reducing the amount of sunlight they receive and, if sulfur aerosols are used, damage the ozone layer.
Indeed, some scientists hesitate to follow the IAD path.
“That we can actually try to control the whole climate is a pretty terrifying idea,” said Douglas MacMartin, senior research associate and lecturer in mechanical and aerospace engineering at Cornell University and research professor in computer science. and mathematical sciences at the California Institute of Technology, says Smithsonian magazine. And the IPCC, in a 2018 discussion of what the panel called Solar Radiation Modification (SRM), concluded that “the combined uncertainties, including technological maturity, physical understanding, potential impacts and governance challenges, limit the ability to implement implement SRM in the near future ”.
Due to these concerns, the SCoPEx team has postponed the maiden voyage of its helium balloon “until a more in-depth societal engagement process can be conducted to address geo-research issues. -solar engineering in Sweden “.
But Keith argued that the real danger is that some maverick organizations are implementing an SAI without the kind of scientific data that SCoPEX wants. The second big objection to SAI research is that governments and businesses that are already reluctant to reduce carbon dioxide emissions will cling to SAI as proof that such reductions are unnecessary.
This could negate any potential benefits of the IAD. Even if the SCoPEx mission is successful and IAD is fully implemented, it will only complement, not replace, carbon dioxide reduction. Lizzie Burns, managing director of Harvard’s solar geoengineering research program, offered a striking analogy: “It’s like a pain reliever. If you need surgery and are taking pain relievers, that doesn’t mean you don’t need surgery anymore.
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