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Reductions in noxious emissions in China have contributed to temperature rises in America and adjacent waters.
This implies that creating atmospheric pollution could be a solution to AGW.
https://www.science.org/content/art...ne in aerosols,scientists report today in the
This implies that creating atmospheric pollution could be a solution to AGW.
https://www.science.org/content/art...ne in aerosols,scientists report today in the
Deadly Pacific ‘blobs’ tied to emission cuts in China
Warming due to cleaner air rippled across the ocean, modeling suggests
- 6 MAY 2024
- 3:30 PM ET
- BYWARREN CORNWALL
In 2015, a blob of warm water off Alaska led to marine die-offs. Did pollution cuts in China supercharge the event?C.L. GENTEMANN, ET AL., GEOPHYS. RES. LETT., 44, 312– 319, (2017), DOI: 10.1002/2016GL071039
Starting in late 2013, the first in a handful of record-shattering heat waves struck the north Pacific Ocean near Alaska. Temperatures in these warm “blobs,” which have occurred four times in the past decade, sometimes reach more than 2°C above normal. They have sparked coastwide blooms of toxic algae, left thousands of humpback whales missing and presumed dead, emptied the nets of Alaska cod fishers, and littered North American beaches with the corpses of starved seabirds.
Research has implicated climate change, which can supercharge natural fluctuations in ocean heat. But now, scientists are pointing to another surprising contributor: China’s success in stemming air pollution. A steep decline in aerosols—tiny airborne particles such as sulfates—emitted by Chinese factories and power plants in the 2010s appears to have amplified a string of extreme heat waves on the other side of the Pacific, driving up to 30% of the temperature increase during these heat waves, scientists report today in the Proceedings of the National Academy of Sciences.
“We have been aware of the important role of aerosol forcing in modulating climate change,” says Hai Wang, a climate modeling expert at the Ocean University of China and an author on the paper. “But we didn’t expect that the warming would increase by that much.”
The new work ties together two phenomena that hadn’t previously been linked, says Dillon Amaya, a climate modeling expert at the National Oceanic and Atmospheric Administration who studies climate impacts in U.S. waters. “There has not been a satisfying explanation” for the spate of heat waves, he says. “This offers a really compelling argument.”
Aerosols can act like tiny mirrors, reflecting sunlight back into space and reducing the amount that reaches Earth’s surface. Eliminate them and the world warms. Scientists last month reported that cleaner air might be responsible for 40% of the increase in heat driving global warming between 2001 and 2019.
Wang and his collaborators wondered whether a drop in aerosol pollution might explain a more geographically specific warming effect. The Pacific heat waves occurred in a part of the ocean that previously seemed unresponsive to rising global temperatures, and they coincided with a pollution crackdown in China that between 2006 and 2017 pushed down emissions by as much as 70% for sulfur dioxide, which reacts in the atmosphere to form sulfate particles.
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To see whether the two developments might be linked, the researchers turned to a dozen computer models that have been used to simulate how the atmosphere and ocean interact to shape global climate, in a coordinated exercise known as the Coupled Model Intercomparison Project (CMIP).
The researchers partly relied on a quirk in different iterations of the project. The models participating in CMIP5 assumed that aerosol pollution over East Asia would flatten, but not drop. The CMIP6 models, however, more closely mimic the actual decline in aerosol pollution. When the researchers ran the models to re-create the climate up to the year 2020, both generations moved in tandem until 2007. Then they diverged. The CMIP6 models showed strong warming in the northeast Pacific, the epicenter of the heat waves.
By peering more deeply into one model, the researchers uncovered a possible explanation. Much as a dropped rock can send waves across a pond, temperature changes in a limited region can ripple across the atmosphere, Wang says. The computer simulations showed a chain reaction in which falling air pollution in China increased warming near the coast of Asia, which amplified a high-pressure system along the Pacific’s western edge. That intensified a neighboring low-pressure system in the middle of the Pacific. A huge low-pressure patch known as the Aleutian Low, off the coast of Alaska, responded by strengthening and expanding southward, which weakened westerly winds that cool the sea surface and set the stage for a heat wave.
These patterns didn’t cause the heat waves, Wang says. Natural fluctuations in the weather did that. But they likely amplified the heat waves’ intensity, as did climate change, by creating conditions “that make these extreme events easier to happen,” he says.
The study covers a relatively short time span and a small number of heat waves in a complex, dynamic ocean, cautions Maria Rugenstein, a Colorado State University scientist who studies interactions between the atmosphere and the tropical Pacific. “It’s kind of statistically not very substantial,” she says of the number of events. “But their physical argument is very solid.”
If the findings hold up, Rugenstein says, they also offer a lesson about the potential consequences of intentionally injecting aerosols high into the atmosphere, a geoengineering strategy some have proposed as a way to cool the planet. The study shows the climate can respond quickly, with unexpected repercussions an ocean away. “I would take this as a cautionary tale,” she says.
