Pale circles on the map show low pollution levels; black spots are the worst. Amid the delicate negotiations in Paris, some political sensitivity may attach to the measurements. "Worse than China" may have become the worldwide shame benchmark for air pollution. Not that any of the delegates would say that out loud in Paris. More diplomatically, US President Barack Obama said the conference needed to do more than "simply" reach an agreement on "rolling back the pollution we put into the skies", emphasising the need to reduce poverty and preserve the planet simultaneously. Chinese President Xi Jinping said any agreement should take into account differences between nations: "Countries should be allowed to seek their own solutions, according to the national interest." A NASA satellite photo shows smog over Beijing on November 30, 2015. The brightest areas are clouds or fog, tinged with yellow or grey because of air pollution. Credit:NASA Earth Observatory When he said that at the start of the conference on Monday, Beijing was choking on the worst air pollution of 2015. NASA satellite images showed Beijing engulfed by a yellow-grey pollution haze while Plume Labs' map had northern China as a mass of black spots where cold-fired power plants had been in overdrive due to a cold snap.

The unofficial air quality index measured at the US embassy in Beijing showed 666 for small particulate matter on Monday. In the US an index over 100 is considered unhealthy, and anything over 300 would trigger an emergency health warning. Small particulate matter (less than 2.5 micrometres) is particularly hazardous to health because it can embed deep in the lungs and even enter the bloodstream directly from there. The Chinese authorities issued an alert advising people to stay indoors. Construction was halted at some sites and some factories were ordered to close, news reports said. The Forbidden City is visible through pollution with the help of Chinese netizens. Credit:Kim Kyung-Hoon The head of the European Union Chamber of Commerce in Beijing, Joerg Wuttke, posted the "view" from his office window:

When Plume Labs' small particulate reading for Paris topped that of Beijing in March, the French government responded by cutting half the cars from the road, according to Plume. As the summit grinds on, the latest readings say current air pollution in Paris is again far worse than in Beijing where the air is deemed "fresh". Paris citizens are warned to use caution exercising or eating outdoors, while for Beijing the advice is to "go for it". For Sydney the air pollution is registering as moderate and "go for it" applies.