The cleanup of air pollution in East Asia has accelerated global warming, a new study published today (Monday, 14 July) in the journal Communications Earth and Environment has found.
Global warming, driven primarily by emissions of greenhouse gases, has been accelerating for the past 15 years, leading to record-breaking surface temperatures. Over the same period, countries in East Asia have made strong efforts to clean up air pollution, which is important for public health. The largest air pollution clean-up has been made in China, where ambient air pollution is responsible for about 1 million deaths a year .
But air pollution has also helped cool the climate. Sulfate aerosols, arising from burning fossil fuels, can shade the Earth's surface from sunlight. Air pollution has therefore inadvertently held in check some greenhouse gas driven warming. The Intergovernmental Panel on Climate Change (IPCC) assessed that in 2021, aerosols cooled the global surface by 0.4 ºC. This, however, did not take into account the fact that since the early 2010s, China, then a major emitter of key constituents of air pollution, has implemented strict policies to improve air quality.
Bjørn H. Samset, lead author and senior researcher at CICERO Centre for International Climate Research, said: "We have been able to single out the climate effects of air quality policies in East Asia over the last 15 years. Our main result is that the East Asian aerosol cleanup has likely driven much of the recent global warming acceleration, and also warming trends in the Pacific."
Analysing the climate effects of emissions from a single region is challenging. It requires climate simulations that have not been readily available and updated emissions data that captures the actual pollution reductions in and around mainland China. Using a large set of simulations from eight different climate models, this study shows how a 75 percent reduction in East Asian sulfate emissions partially unmasks greenhouse gas driven warming, and changes how temperatures rise in different parts of the world.
Dr Laura Wilcox, contributing author and associate professor at the National Centre for Atmospheric Science (NCAS) in the University of Reading, said: "The climate effects of air pollution are short-lived, while the impact of carbon dioxide emissions can be felt for centuries. This means that the acceleration of warming due to reductions in air pollution is also likely to be short-lived. We will see an acceleration of warming while the unmasking takes place, and then a return to a greenhouse-gas driven rate of warming as air pollution stabilises."
