In trying to reduce air pollution, China may have sped up global warming: Study

While attempting to improve air quality in China and across East Asia, regulators may have inadvertently contributed to a rise in global warming, according to a new study. Fewer aerosol emissions, which can also be used as a method to cool the Earth by absorbing sunlight, could increase temperatures by roughly 0.05 degrees Celsius each decade beginning in 2010, the study authors said.

The findings were published Monday, July 14, in Communications Earth & Environment.

Stricter air quality regulations with unintended consequences

China was able to reduce the emission rates of toxic sulfur dioxide by 75% after implementing strict air quality regulations, researchers noted. However, while sulfur dioxide gas is harmful to plants, humans and other animals, its particles are among the aerosols that are used to cool the planet. Sulfur dioxide comes from the burning of fossil fuels and volcanoes. 

Prior research on aerosols and sunlight

As Straight Arrow News previously reported, when clouds form around certain aerosols, their particles absorb solar energy from the atmosphere and work to dim sunlight on the ground below.  In the absence of clouds, these aerosols can still reflect sunlight away from Earth and back into space.

Prior to China’s aggressive air quality control policies, pollution had been the leading cause of premature death in the nation, the authors of the study said. But, with fewer cooling aerosols in the air, areas of East Asia and around the globe have seen greater warming and are predicted to suffer from more extreme heat and changing monsoon patterns, which could lead to harmful impacts on the agricultural industry, as noted in the study.

The findings of the newest study

The falling sulfate levels “partially unmasks greenhouse-gas driven warming and influences the spatial pattern of surface temperature change,” the researchers wrote.

“Reducing air pollution has clear health benefits, but without also cutting CO2, you’re removing a layer of protection against climate change,” Robert Allen, study co-author and climatology professor at the University of California, Riverside, said in a statement. “It highlights the need for parallel efforts to improve air quality and reduce greenhouse gas emissions.”

Methodology

Allen and fellow researchers discovered the phenomenon of fewer aerosols causing warmer temperatures through simulations using major climate models from the years 2015 to 2049. Through the use of data from the Regional Aerosol Model Project, which includes assistance from the United States, Europe and Asia, the researchers were able to project how much temperatures have warmed and may continue to warm in the future.

Future climate change mitigation efforts

While the study focused on sulfate aerosols, the scientists involved in the research emphasized that carbon dioxide and methane emissions are the biggest contributors to long-term climate change.

“Our study focused on the recent, dramatic speedup in global warming, which is very concerning but still small compared to the overall, long-term amount of warming from increased CO2 and methane,” the lead author of the study, Bjørn Samset, a senior researcher at the Center for International Climate and Environment Research in Norway, said in a statement.

Allen also acknowledged that because aerosols have a short lifespan in the atmosphere, their impact on rising temperatures may also be short-lived.

“Sulfur dioxide and sulfate aerosols have lifetimes of about a week,” Allen said. “Once they’re removed, we’ll eventually settle back into a warming rate that’s more consistent with the long-term trend.”

Researchers say that as countries across the globe begin to eliminate the use of aerosols, they plan to examine any potential shifts that could influence future climate trends.