London -
When we think of choking smog, the first city that comes to mind is Beijing, China, but it seems that London, UK is running a close second, a statistic that has been called a "public health emergency."
Using new, high-resolution global satellite maps of air quality indicators, NASA scientists have tracked air pollution trends over the past decade. The latest maps show emissions of NO2 have gone up significantly over South Asia.
This global map shows the concentration of nitrogen dioxide in the troposphere as detected by the Ozone Monitoring Instrument aboard the Aura satellite, averaged over 2014.
