- 3233 - EARTH - is it heating up? - In 2021, Earth reached a concentration of carbon dioxide (CO2) in the atmosphere that hit 150% of its value in preindustrial times. To prevent these worst effects of climate change, the world needs to decrease net emissions of carbon dioxide to zero by 2050. What is the plan?
------------------ 3233 - EARTH - is it heating up?
- Even if we were to achieve this reduction goal, it wouldn't put a sudden brake on the temperature rise, because it takes time to see the effects of CO2 reductions on global temperatures; the negative impacts of global warming will continue for decades.
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- To counteract this it might be possible to achieve a temporary reduction in global temperatures by tweaking the composition of Earth's upper atmosphere. Researchers were hoping to test some of this technology in the Stratospheric Controlled Perturbation Experiment (SCoPEx).
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- The ultimate source of Earth's heat is the sun, which bathes the daytime side of the planet in a constant flow 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 radiated back into space at night.
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- In the delicate balance that prevailed in preindustrial times, the incoming heat was exactly offset by the amount lost to space, ensuring average global temperatures remained constant.
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- The problem by 2021 is that CO2 emissions have grown to disrupt this balance by absorbing some of the heat that should be radiated 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 prevent the worst effects of this climate change.
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- Other processes can produce short-term reductions in global temperature. Volcanic eruptions blast clouds of dust particles high up into the stratosphere, an upper layer of the atmosphere, forming a protective shield that prevents some of the sun's heat from reaching Earth's surface.
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- The 1991 eruption of Mount Pinatubo in the Philippines caused the average temperature in the Northern Hemisphere to drop by about 1 degree Fahrenheit over the following 15 months. The SCoPEx team wants to take a page from such eruptions by injecting particles into the upper atmosphere in order to lower temperatures the same way.
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- The basic idea or stratospheric aerosol injection, or SAI, is simple. A high-flying aircraft or helium balloon would dispense batches of microscopic particles called aerosols into the stratosphere at altitudes of 12.4 miles, or more, much higher than planes usually fly. The aerosols would remain suspended in the air, too tiny to be visible as clouds from the ground but opaque enough to reflect a fraction of the sun's energy back into space.
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- In simulations, SAI appears to be a viable concept. A fleet of high-flying aircraft could deposit sufficient aerosols to offset current levels of global warming. But the aerosols would have to be replenished every few years, and the method tackles only one of the symptoms of climate change rather than addressing its root cause, the greenhouse effect. It is a stopgap measure, countering rising temperatures while countries simultaneously reduce carbon dioxide levels and lessening the greenhouse effect.
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- The research into SAI has been theoretical, supplemented by a limited amount of real-world data from volcanic eruptions. SCoPEx wants to make real-world measurements under carefully controlled conditions, allowing better calibration of their computer models.
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- Volcanoes mainly eject sulfur-based compounds. But these compounds not only cool the atmosphere but also damage Earth's protective ozone layer, which shields us from harmful UV radiation.
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- The SCoPEx team is focusing on a less harmful aerosol, calcium carbonate, chalk dust, which researchers hope will produce the desired cooling effect without harming the ozone layer.
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- The team wants to deploy a large, uncrewed helium balloon that would be similar to a standard weather balloon except that it would be fitted with propellers to allow the team on the ground to maneuver it in a controlled way.
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- On its first flight, which is tentatively planned for next year, the balloon would not release anything into the stratosphere. Instead, it would ascend to an altitude of 12.4 miles, where the team would test the maneuvering system and check that all the scientific instruments and communications function correctly.
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- A second flight would perform a controlled release of 2.2 to 4.4 pounds of calcium carbonate at the same altitude. The balloon would be moving steadily in a straight line during the release, so the aerosol particles would form a narrow plume around 0.6 miles in length.
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- The balloon would then turn back through the plume, observing how the particles disperse over time and measure the extent to which they reflect sunlight.
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- The goal is simply to improve our models of the way aerosols form in the stratosphere.
At least another decade of research will be needed before there is a large-scale aerosol release. This aerosol release might involve injecting around 1.5 million tons into the stratosphere per year. Roughly a hundred aircraft would need to continuously fly payloads up to about 12 miles altitude.
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The SAI plan remains highly controversial. One concern is that humans created the climate crisis in the first place by pumping greenhouse gases into the atmosphere, so how can people be sure that pumping aerosols into it will make things better? Maybe create a different problem?
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- Although computer modeling suggests SAI is safe, there's still the possibility that it might have unforeseen side effects. There is the possibility that it could disrupt weather patterns, harm crops by reducing the amount of sunlight they receive, and if sulfide aerosols are used damage the ozone layer.
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- Even if the SCoPEx mission is successful and SAI is fully implemented, it will only supplement, not replace, carbon dioxide reduction. Can mankind engineer their way out of this problem?
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- July 26, 2021 EARTH - is it heating up? 3234
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