Gas meter in space

Tropomi sees how polluted the air is everywhere on Earth

Never before have we had such a clear view of global air pollution and the development of the climate. What has changed that? A new Dutch instrument, for one.

Text: Mark Traa

The European satellite Sentinel-5 Precursor has been orbiting the Earth since October 2017. On board is Tropomi: the Tropospheric Monitoring Instrument. This device makes precise measurements of the atmospheric composition. For example, it measures the amount and location of carbon monoxide, methane, nitrogen dioxide and ozone in the atmosphere. This provides scientists with a better understanding of how our air quality and our climate are changing.

The distribution of polluting gases varies across the world. In the Netherlands, traffic and industry emit large amounts of nitrogen dioxide. Thanks to Tropomi, from now on we see exactly where these gases originate, how their density changes over time and the weather’s impact on this. Another nice touch: the path of Tropomi’s orbit (around the poles) means that every day each place on Earth is viewed at the same local time. It’s perfect for comparing situations occuring at the same time of the day.

The data Tropomi transmits is not always reassuring, but it’s extremely useful because it enables us to see what kind of invisible garbage we send into the atmosphere.

Tropomi is the result of a partnership between several parties: Airbus Defence and Space Netherlands, KNMI, SRON and TNO, commissioned by NSO and ESA.

A single space-borne image reveals where the most nitrogen dioxide is emitted. Never before has this been so clearly illustrated. Tropomi succeeded in doing so on November 7th 2017. The (red) plumes around industrial areas are clearly visible.

Ten days after the first photo, the Netherlands had a supply of clean air from the north-west. And it showed: the concentrations of nitrogen dioxide immediately decreased.

A world map that makes instantly clear where most of the carbon monoxide is emitted. Thanks to Tropomi. The air pollution above Asia is clearly visible. A great deal of carbon monoxide is emitted there by industry, transport and households. The pollution increases in November when farmers burn agricultural waste following the harvest to clean up their fields. Things look bad above South America (deforestation), Africa and Australia as well (forest and savannah fires).