As much as Chinese authorities need resolve to tackle air pollution, they also require encouragement. A study by scientists from China, France and the United States provides that, contending that the switch to cleaner energy sources is working. They say that if the present strategy remains in place, the almost year-round blue skies of the 1970s could return to big cities by 2030. It is a tantalising vision that necessitates an unwavering dedication to moving away from coal and oil, no matter what the costs and pressures. The optimistic outlook is based on analysis of data from urban areas, with the most encouraging signs from progress in fighting the most dangerous air pollutant, fine particles known as PM2.5. Named for their size in micrograms, the particles largely come from power plants, vehicles and burning fuel for heating and can cause serious health problems with prolonged exposure. The study, published in the journal Science Advances, believed levels may have peaked a few years ago at an average of about 60 micrograms per cubic metre of air. Projecting improvements to 2030 with the continued shift towards use of cleaner energy sources such as natural gas, nuclear power and solar, even a modest decrease of 5 micrograms would return air quality to pre-1980 levels, researchers’ calculations show.

Heavily polluted cities such as Beijing and Shanghai were much different 40 years ago; there were few factories, life was simpler and people got around by bicycle. Decades of rapid economic growth fuelled by industrialisation changed that, and the air in many of China’s largest cities is among the most choking in the world. Authorities well know what that means for health, development and image, and have put in place tough targets and a shift towards cleaner industries. They were the basis for China’s pledges when signing up to and taking a leading role in the Paris accord on climate change.