Research: China’s Clear Air Insurance policies are Triggering Further International Warming

Study: China’s Clean Air Policies are Triggering Additional Global Warming

This is a photo taken in the city of Taiyuan, China shows haze on December 3, 2016.
CREDIT Courtesy of Yuhang Wang

Guest essay by Eric Worrall

According to a study whose authors include Ken Caldeira, China’s efforts to eliminate its infamous air pollution could cause an additional 0.1C NH warming, because less sunlight will be reflected by aerosols. However, despite suggesting China’s improved air quality is a “climate setback”, Caldeira acknowledged cleaner air is a net improvement.

China’s Success in Improving Air Quality by Cutting Polluting Emissions May Worsen Climate Change 


China’s success in improving air quality by cutting polluting emissions may have a negative knock-on effect on climate change overall, a new study has found.

The research, by scientists from Carnegie Institution for Science, USA, Chinese Academy of Environmental Planning, China, Tsinghua University, China, and the University of California Irvine, USA, used modeling to analyze the effect China’s success in reducing emissions such as sulfur dioxide, black carbon, and organic carbon, has had on global climate change. Their results are published today in the IOP Publishing journal Environmental Research Letters.

Lead author Dr. Yixuan Zheng, from Chinese Academy of Environmental Planning, a former postdoc at Carnegie Institution for Science, said: “Economic growth and industrialization in China over the recent decades has been supported by increasing consumption of energy from coal, making China the world’s largest emitter of major air pollutants such as sulfur dioxide and black carbon. These pollutants have significant impacts on air quality and public health, so China put stringent measures in place to reduce them. The measures were effective, and aerosol pollution in China was substantially alleviated after 2013, with notable public health benefits.”

Dr. Zheng said: “Anthropogenic sulfate aerosol was estimated to cool the earth on average by half a degree centigrade in 2010, equivalent to 76 percent of all-anthropogenic-aerosols-induced cooling. Black carbon, on the other hand, absorbs heat in the atmosphere and warms the Earth. So, understanding the effect reduction in these materials could have on warming is essential for future climate mitigation strategies.”

Carnegie’s Professor Ken Caldeira, also a co-author, said: “Cleaning up aerosol emissions has tremendous health benefits, but unmasks some global warming. While this may seem like a climate setback, we need healthy people to help tackle the climate problem, and if we are to have more resources to allocate to better energy systems, we need to be spending less on the health damage caused by our aerosols. Helping people to become healthier can be a win for the climate system, even if it does directly lead to some warming.”

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The abstract of the study;

Climate effects of China’s efforts to improve its air quality

Yixuan Zheng, Qiang Zhang, Dan Tong, Steven J Davis and Ken Caldeira

Published 29 September 2020

Facing severe air pollution issues, China has implemented a series of clean air policies aimed to improve the country’s air quality. These policies largely focused on reducing emissions of major air pollutants such as sulfur dioxide (SO2) and primary aerosols. However, changes in such pollution also affect radiative forcing. To understand the climate consequences of these clean air actions in China, we evaluate the near-equilibrium climate response to sustained changes in aerosol (and precursors) emission rates equivalent to those that occurred in China between 2006 and 2017. During this period, China’s SO2 emissions declined by ~70%, and black carbon emissions declined by ~30%. Climate simulations that used a fully coupled ocean and atmosphere climate model indicate that China’s reductions in aerosol emission rates from 2006 to 2017 may exert a net increase in global radiative forcing of 0.09 ± 0.03 W m−2 and a mean warming of 0.12 ± 0.01 °C in the Northern Hemisphere; and may also affect the precipitation rates in East Asia and in more distant regions. The success of Chinese policies to further reduce aerosol emissions may bring additional net warming, and this ‘unmasked’ warming would in turn compound the challenge and urgency of international climate mitigation efforts.

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The study authors also claim that the lower aerosols have increased precipitation slightly, especially in the East, which has experienced severe floods this year.

It is nice to see an author of a climate paper acknowledge some things are worse than global warming.

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