Increase in tropospheric nitrogen dioxide over China observed from space

Emissions from fossil fuel combustion and biomass burning reduce local air quality and affect global tropospheric chemistry. Nitrogen oxides are emitted by all combustion processes and play a key part in the photochemically induced catalytic production of ozone, which results in summer smog and has increased levels of tropospheric ozone globally(1). Release of nitrogen oxide also results in nitric acid deposition, and - at least locally - increases radiative forcing effects due to the absorption of downward propagating visible light(2). Nitrogen oxide concentrations in many industrialized countries are expected to decrease(3), but rapid economic development has the potential to increase significantly the emissions of nitrogen oxides(4-7) in parts of Asia. Here we present the tropospheric column amounts of nitrogen dioxide retrieved from two satellite instruments GOME(8,9) and SCIAMACHY(10) over the years 1996 - 2004. We find substantial reductions in nitrogen dioxide concentrations over some areas of Europe and the USA, but a highly significant increase of about 50 per cent - with an accelerating trend in annual growth rate - over the industrial areas of China, more than recent bottom-up inventories suggest(6).