Scientists from SRON Netherlands Institute for Space Research and the Karlsruhe Institute for Technology (KIT) have developed a highly accurate method to derive concentrations of the greenhouse gases CO₂ ‑­ and methane from observations of Japanese GOSAT satellite. GOSAT has been launched in January 2009 but till now the carbon dioxide and methane data lacked sufficient accuracy. The newly derived data have the accuracy to significantly improve our understanding of the sources and sinks of greenhouse gases in the Earth atmosphere.

Since pre-industrial times the concentrations of man-made greenhouse gases have increased dramatically. For future climate change prediction it is essential to develop realistic scenarios of how the greenhouse gas concentrations will evolve. This requires a thorough understanding of the sources that emit greenhouse gases in the atmosphere and the sinks that remove them. For example, only about half of the emitted CO₂ remains in the atmosphere. The other half is removed by the combined action of the oceans and land.

Since the capacity for carbon storage is limited it is expected that the sinks will increasingly fail to keep up with the emissions in the future. With the current understanding of sources and sinks it is hard to predict when this will happen. "To improve our understanding, highly accurate global measurements of greenhouse gases are crucial," says Sandrine Guerlet, one of the researchers involved in the development of the new method..

First satellite

GOSAT is the first satellite dedicated to observe greenhouse gas concentrations from space. The satellite measures sunlight reflected from the Earth surface and atmosphere at different colors. CO₂ and methane absorb light at specific colors and hence the amount of light measured depends on the amount of CO₂ and methane in the atmosphere. To derive the concentrations of these gases it is needed to model the path that the sunlight travels through the atmosphere. The scientists from SRON and KIT developed a novel method for this (funded by the NWO Gebruikers Ondersteunings GO programma). The resulting GOSAT CO₂ and methane data have unprecedented accuracy, which was demonstrated by comparing the data with independent measurements performed from the ground.

Scientists

The GOSAT CO₂ and methane data derived by the SRON scientists are part of ESA’s Essential Climate Variables project on greenhouse gases and as such will be made available to a broad user community. The high accuracy of the retrievals has also been recognized by the Japanese GOSAT team (JAXA, NIES, MOE Ministry of Environment) resulting in a collaboration between the retrieval team at SRON and KIT and the GOSAT team.

The results were published on 30 July 2011 in the Geophysical Research Letters.