New maps that use information from the Copernicus Sentinel-5P satellite reveal emissions of nitrogen dioxide along a Siberian natural gas pipeline that connects the Urengoy gas field – the second-largest gas field in the world – with Europe.

The Urengoy–Pomary–Uzhhorod pipeline is one of Russia's main natural gas export pipelines. In order to maintain the pressure and flow over long distances, a series of compressor stations are strategically placed to help push the gas along.

Compressor stations typically run on gas-powered turbines, and their high-temperature combustion usually leads to small quantities of nitrogen dioxide emissions being lost to the atmosphere.

Until now, it has proved difficult to measure trace-gas concentrations over snow-covered regions such as Siberia, northern Europe and Canada, as it has been very difficult to distinguish clouds from snow and ice in the data retrieval algorithms – considering snow and clouds appear equally bright and cold.