Global Changes in the Atmosphere Guided Reading and Study Answers
As Climate Disasters Pile Up, a Radical Proposal Gains Traction
The idea of modifying Earth's atmosphere to cool the planet, once seen as too risky to seriously consider, is attracting new money and attention.
WASHINGTON — As the effects of climate change become more devastating, prominent research institutions and government agencies are focusing new money and attention on an idea once dismissed as science fiction: Artificially cooling the planet, in the hopes of buying humanity more time to cut greenhouse gas emissions.
That strategy, called solar climate intervention or solar geoengineering, entails reflecting more of the sun's energy back into space — abruptly reducing global temperatures in a way that mimics the effects of ash clouds spewed by volcanic eruptions. The idea has been derided as a dangerous and illusory fix, one that would encourage people to keep burning fossil fuels while exposing the planet to unexpected and potentially menacing side effects.
But as global warming continues, producing more destructive hurricanes, wildfires, floods and other disasters, some researchers and policy experts say that concerns about geoengineering should be outweighed by the imperative to better understand it, in case the consequences of climate change become so dire that the world can't wait for better solutions.
"We're facing an existential threat, and we need to look at all the options," said Michael Gerrard, director of the Sabin Center for Climate Change Law at the Columbia Law School and editor of a book on the technology and its legal implications. "I liken geoengineering to chemotherapy for the planet: If all else is failing, you try it."
On Wednesday, a nonprofit organization called SilverLining announced $3 million in research grants to Cornell University, the University of Washington, Rutgers University, the National Center for Atmospheric Research and others. The work will focus on practical questions, such as how high in the atmosphere to inject sunlight-reflecting aerosols, how to shoot the right size particles into clouds to make them brighter, and the effect on the world's food supply.
Kelly Wanser, SilverLining's executive director, said the world is running out of time, and protecting people requires trying to understand the consequences of climate intervention. She said the goal of the work, called the Safe Climate Research Initiative, was "to try to bring the highest-caliber people to look at these questions."
The research announced Wednesday adds to a growing body of work already underway. In December, Congress gave the National Oceanic and Atmospheric Administration $4 million to research the technology. NOAA will also start gathering data that will let it detect whether other countries start using geoengineering secretly. And Australia is funding experiments to determine whether and how the technology can save the Great Barrier Reef.
"Decarbonizing is necessary but going to take 20 years or more," Chris Sacca, co-founder of Lowercarbon Capital, an investment group that is one of SilverLining's funders, said in a statement. "If we don't explore climate interventions like sunlight reflection now, we are surrendering countless lives, species, and ecosystems to heat."
One way to cool the earth is by injecting aerosols into the upper layer of the atmosphere, where those particles reflect sunlight away from the earth. That process works, according to Douglas MacMartin, a researcher in mechanical and aerospace engineering at Cornell University whose team received funding. "We know with 100 percent certainty that we can cool the planet," Dr. MacMartin said in an interview.
What's still unclear, he added, is what happens next.
Temperature, Dr. MacMartin said, is a proxy for a lot of climate effects. "What does it do to the strength of hurricanes? What does it do to agriculture yields? What does it do to the risk of forest fires?"
To help answer those questions, Dr. MacMartin will model the specific weather effects of injecting aerosols into the atmosphere above different parts of the globe, and also at different altitudes. "Depending on where you put it, you will have different effects on the monsoon in Asia," he said. "You will have different effects on Arctic sea ice."
Another institution getting money as part of the new initiative is the National Center for Atmospheric Research in Boulder, Colo., which is funded by the National Science Foundation and has what its researchers call the world's most sophisticated earth system model.
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The grant from SilverLining will pay for the center to run and analyze hundreds of simulations of aerosol injection, testing the effects on weather extremes around the world. One goal of the research is to look for a sweet spot — the amount of artificial cooling that can reduce extreme weather events, without causing broader changes in regional precipitation patterns or similar impacts.
"Is there a way, in our model world at least, to see if we can achieve one without triggering too much of the other?" said Jean-Francois Lamarque, director of the center's Climate and Global Dynamics laboratory.
NOAA is starting its own research into solar geoengineering. And in August, the agency announced that it would begin measuring aerosol levels in the stratosphere, creating a baseline so the agency can tell if those levels change later.
One of the advantages of having that information, according to Troy Thornberry, a research scientist at NOAA who studies atmospheric composition and chemical processes, is that it would let NOAA determine if aerosol levels increase — a sign that some other country may be intentionally injecting aerosol without announcing it.
Injecting aerosol into the stratosphere isn't the only way to bounce more of the sun's rays back into space. The Australian government is funding research into what's called "marine cloud brightening," which is meant to make clouds more reflective by spraying saltwater into the air. The goal is to get salt particles to act as nuclei in those clouds, encouraging the formation of many small water droplets, which will increase the brightness of the clouds.
Australian researchers say they hope the technique can save the Great Barrier Reef. Rising water temperatures during so-called marine heat waves are accelerating the die-off of the reef, and making marine clouds more reflective may be able to cool water temperatures enough to slow or stop that decline.
In March, Daniel Harrison, a biological oceanographer at Southern Cross University in Australia, tested the technology by using 100 nozzles to spray water into the air.
"The results were quite encouraging," Dr. Harrison said in a phone interview. One of the challenges, he said, will be using the technology on a large enough scale to make a difference. He estimated it would probably take 500 to 1,000 stations such as barges or platforms spraying water, or a smaller number of moving vessels, to cover the entire reef.
The University of Washington is also working on marine cloud brightening and was another recipient of a SilverLining grant. Sarah Doherty, program manager for the university's Marine Cloud Brightening project, said the challenge would be building spray nozzles that consistently produce the right size particles. between 30 and 100 nanometers, and finding ways to prevent them from sticking together.
The project aims to understand how the clouds respond, and also predict the regional and global climate response. Dr. Doherty said her team hoped to field-test the spray system in the next 12 to 18 months.
"The whole idea of the research we're doing," she said, "is to make sure you don't go out and inadvertently change things in a way that's going to cause damage."
Global Changes in the Atmosphere Guided Reading and Study Answers
Source: https://www.nytimes.com/2020/10/28/climate/climate-change-geoengineering.html
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