Pollution paradox: How cleaning up smog drives global warming

Pollution paradox: How cleaning up smog drives global warming

Fred Pearce writes:

They call it “The Blob.” A vast expanse of ocean stretching from Alaska to California periodically warms by up to 4 degrees Celsius (7 degrees F), decimating fish stocks, starving seabirds, creating blooms of toxic algae, preventing salmon returns to rivers, displacing sea lions, and forcing whales into shipping lanes to find food.

The Blob first formed in 2013 and spread across an area of the northeast Pacific the size of Canada. It lasted for three years and keeps coming back — most recently last summer. Until now, scientists have been unable to explain this abrupt ocean heating. Climate change, even combined with natural cycles such as El Niño, is not enough.

But new analysis suggests an unexpected cause. Xiaotong Zheng, a meteorologist at the Ocean University of China, and international colleagues argue that this extraordinary heating is the result of a dramatic cleanup of Chinese air pollution. The decline in smog particles, which shield the planet from the sun’s rays, has accelerated warming and set off a chain of atmospheric events across the Pacific that have, in effect, cooked the ocean.

Other researchers spoken to by Yale Environment 360 see the finding, made with the help of in-depth climate modeling, as having potentially critical implications for future climate in the Pacific and elsewhere. Emissions of the tiny particles that cause smogs, collectively known as aerosols, are in decline across most of the world — apart from South Asia and Africa. Scientists are concerned that the cleanups will both heat the global atmosphere and lead to more intense regional ocean heat waves.

Yangyang Xu, an atmospheric scientist at Texas A&M University not involved in the study, said it shows that “aerosol reductions will perturb the climate system in ways we have not experienced before. It will give us surprises.”

Indeed, that may already be happening in the Atlantic. Some researchers we spoke to argue that the exceptional heat wave that spread across the North Atlantic from spring last year until April this year, sending fish fleeing for cooler Arctic waters, may have owed its intensity to international efforts to reduce aerosol emissions from ships crossing the ocean. [Continue reading…]

The Guardian reports:

The slashing of pollution from shipping in 2020 led to a big “termination shock” that is estimated have pushed the rate of global heating to double the long-term average, according to research.

Until 2020, global shipping used dirty, high-sulphur fuels that produced air pollution. The pollution particles blocked sunlight and helped form more clouds, thereby curbing global heating. But new regulations at the start of 2020 slashed the sulphur content of fuels by more than 80%.

The new analysis calculates that the subsequent drop in pollution particles has significantly increased the amount of heat being trapped at the Earth’s surface that drives the climate crisis. The researchers said the sharp ending of decades of shipping pollution was an inadvertent geoengineering experiment, revealing new information about its effectiveness and risks.

High ocean surface temperatures smashed records in 2023, alarming experts who have struggled to explain the huge rises. But scientists have mixed views on the role played by the cut in shipping pollution. [Continue reading…]

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