Recent scientific investigations reveal a surprising link between reduced smog levels in China and extreme heat events across the Pacific.
Efforts to clean up air pollution, crucial for public health, may inadvertently heat the atmosphere.
A phenomenon dubbed “The Blob” refers to unusually warm ocean waters stretching from Alaska to California.
This event, which can elevate temperatures by up to 4 degrees Celsius, severely impacts marine life. Fish stocks dwindle, seabirds starve, toxic algae bloom, salmon fail to return to rivers, sea lions get displaced, and whales enter shipping lanes searching for food.
Emerging in 2013, The Blob occupied an area as vast as Canada and persisted for three years. It has resurfaced multiple times since, most recently in summer.
Scientists previously struggled to explain these sudden increases in ocean temperature. Conventional climate change and natural cycles like El Niño didn’t provide enough justification.
However, a new perspective has surfaced. Researchers under Xiaotong Zheng, a meteorologist at the Ocean University of China, suggest that a significant reduction in Chinese air pollution might be a key factor.
Decreasing smog particles, which usually block some solar energy, accelerates atmospheric warming.
This, in turn, triggers a series of climate events over the Pacific, effectively heating the waters.
Experts contacted by Yale Environment 360 suggest that this discovery, made possible through advanced climate modeling, could have vital consequences for future climate conditions over the Pacific and other regions.
Aerosol emissions are declining globally, except in South Asia and Africa.
Thus, the decrease in these particles is likely to amplify global warming and increase the frequency of intense oceanic heatwaves.
Scrutiny
The concept that pollution reduction could increase atmospheric warming may seem paradoxical.
Yangyang Xu, an atmospheric scientist from Texas A&M University, not involved in the study, notes that reducing aerosols can disrupt the climate system in unforeseen ways.
Aerosols, tiny particles in the atmosphere, are different from greenhouse gases. Instead of trapping heat, aerosols reflect sunlight and sometimes promote cloud formation.
While these particles don’t persist long in the atmosphere, scientists estimate they counteract up to a third of greenhouse warming while present.
Yet, the influence of aerosols has diminished globally in recent years. Clean-air laws in Europe and North America have significantly reduced aerosol emissions since the 1980s.
Over the past decade, China has achieved similar results, with a 70% reduction in aerosols due to strict governmental policies initiated in 2013.
Thus, fewer anthropogenic aerosols are floating in the air than in previous decades.
According to Susanne Bauer from NASA’s Goddard Institute for Space Studies, this trend started in the early 21st century and is expected to continue as more nations aim to eradicate smog.
Consequently, the protective “aerosol mask” is thinning, leading to boosted global warming in various areas.
Ben Booth from the UK Met Office asserts that aerosol removal is presently enhancing greenhouse-gas-driven global warming.
Analysis
Predictions of reduced aerosol cooling have already factored into the Intergovernmental Panel on Climate Change (IPCC)’s future global warming forecasts.
Zheng and Hai Wang from the Ocean University of China, with colleagues from the United States and Germany, revealed through climate modeling that the cleanup of Eastern China’s polluted air has initiated exceptional atmospheric warming over the Pacific. This change has intensified the Aleutian Low, reducing wind speeds that cool the ocean, setting up conditions for extreme ocean warming.
These phenomena serve as warnings for more frequent, larger warm-blob events in the future.
Aerosols, ranging from visible dust and soot particles to invisible ones, come from both natural sources like forest fires and man-made sources like fossil fuel combustion.
Since the Industrial Revolution, the atmospheric load of aerosols has surged, primarily due to human activities involving coal and oil burning.
These emissions include large amounts of sulfur dioxide (SO2), which reacts in the air to form particles that block solar radiation and aid cloud formation. Combustion of fossil fuels produces both warming carbon dioxide and cooling aerosols.
Atmospheric temperatures hinge on the balance between these two factors. The 2021 IPCC climate assessment estimated that greenhouse gases caused a warming effect of about 1.5 degrees Celsius, with aerosols masking 0.4 degrees of this effect.
Without aerosol cooling, temperatures would have already surpassed the 1.5-degree threshold, defined as “dangerous” by the Paris Agreement, says Johannes Quaas from the University of Leipzig and a former IPCC lead author.
But the balance is shifting as more countries work to lower aerosol emissions.
Interestingly, until recently, ship-emitted aerosols likely had a cooling effect that exceeded their warming greenhouse-gas emissions.
This change is driven by a growing awareness of aerosols’ public health impacts, which the World Health Organization reports cause over 4 million premature deaths from various diseases each year. Air pollution decreases life expectancy significantly, and the ongoing efforts to curb aerosol emissions could lead to more significant climatic shifts.
The unique balance of aerosol-induced cooling and greenhouse gas-induced warming can create unexpected climate outcomes, particularly in regions undergoing swift environmental changes.
As nations continue to clean their air for health reasons, these refined balances will challenge current climate models and predictions, requiring constant updates and recalibrations for accuracy.
Continuing to monitor these phenomena will be crucial in understanding and mitigating future warming events.
