China may have found itself once again in the news for the choking smog which blanketed many of its cities over the past month, but pollution in the world's number two economy actually eased in 2015, data compiled by Greenpeace shows. The data, which covers 367 cities, showed average PM2.5 levels dropping by 10% in 2015 compared with the previous year.

However, even with the improvement, 80% of the cities in the survey still failed to meet national air quality standards.

Greenpeace climate and energy campaigner Dong Linsai said: "The biggest trend we've seen is that, although we saw serious smog in the winter of the fourth quarter that's just passed, for the overall trend for the year most of the cities in China have seen improvements air quality. This shows that China has had some success in improving its air quality."

After decades of unbridled economic growth, China's leadership has vowed to crack down on severe levels of air, water and soil pollution, including the heavy smog that often blankets major cities. On top of central government initiatives to crack down on pollution, some local governments have also introduced their own smog-busting initiatives.

Hebei's Baoding city, consistently amongst the top 10 most-polluted, implemented a December-long enforcement of odd-even license plate restrictions and total ban on outdoor construction for December. But some cities have been less proactive in tackling smog, and Dong said he believed this is the reason why Shanghai saw an increase of 3.14% in average PM 2.5 levels.

"In this air quality ranking we've seen that Shanghai's (average pm 2.5) concentration has increased. This could be because according to a legal clause Shanghai should have put forward a goal for controlling and reducing coal consumption by June 2015, but so far Shanghai still hasn't put forward this goal. This (the poor data for Shanghai) could be Shanghai not reaping the benefits from setting an emissions standard and a goal for coal consumption, and could be the reason for the differences between provinces," he said.

More leadership from the central government on tackling coal is needed if China wants to see sustained decreases in PM 2.5 levels, said Dong. China saw a fall of 3.5 in coal production in 2015, official data released on 19 January showed, in part due to declines in key coal consuming industries like steel production and power generation.

"Now we've seen some eastern provinces putting forward regional goals for controlling coal consumption, but so far we haven't seen a national one. If we want to solve this problem on a greater scale in China, Greenpeace has consistently been calling for a national goal on controlling the amount of coal consumption in the upcoming 13th five year plan. Only once this goal has been included can China take the next step to speed resolving the air pollution issue," Dong added.