Beijingers have gotten an unexpected glimpse of seldom-seen blue sky the past several days, following meteorologists' forecast of medium pollution during the Asia-Pacific Economic Cooperation (APEC) summit from November 5 to 11.

Many Beijing residents thought the local government had managed to strike a meaningful blow against air pollution, but environmentalists warned that blue skies have come at the cost of GDP losses that cannot be sustained.

During a November 4 conference forecasting the weather for the APEC summit, meteorologists said that Beijing would see medium or severely polluted air from Saturday, November 8 to Tuesday, November 11, with pollutants from neighboring provinces transported to Beijing by wind from the south.

However, during the weekend just passed, Beijing's air quality index went no higher than 100, the upper limit of the range labeled "good" by the Beijing Municipal Environmental Protection Bureau. The temperature ranged from 2 C to 10 C.

Some Beijing residents also joked about the rare good weather as they enjoyed the blue skies, suggesting APEC might stand for "Air Pollution Eventually Controlled," while one wit coined the phrase "APEC Blue" to describe something good and beautiful that is also fragile and short-lived.

Many pictures featuring blue skies tagged with the keywords "APEC Blue" were posted on Weibo and WeChat, expressing the mixed feelings brought the brief spell of beautiful late-fall weather.

Environmentalists shared the view that the Chinese government had managed to bring air pollution under control during the summit.

"Government policies have played a very important role in the good weather, but it's also cost Beijing and its neighboring cities an enormous amount in manpower and economic losses," said Ma Jun, director of the Institute of Public and Environmental Affairs. Among the strict steps taken by Beijing to cut emissions from factories and vehicles were a six-day holiday for employees at institutes and schools and the suspension of work at all construction sites. The capital also worked with neighboring regions including Tianjin to implement pollution control measures.

But environmentalist also said Beijing has made sacrifices to get back its blue skies that are not sustainable over the long term.

The government's actions took the form of mandatory administrative orders that had negative impact on people's ordinary lives and long-term GDP growth, Ma said.

Ma declined to provide an estimate  of economic losses, saying that estimating an exact number was difficult.

To deal with the air pollution over the long run, Zhang Yuanxun, an environmental professor at the Chinese Academy of Sciences, suggested that   requiring factories in Beijing and its adjacent areas to comply with national emissions standards, and encouraging commuters to take public transportation to work.