Higher temperatures on the earth's surface at higher latitudes cause an increase in the emission of methane, a greenhouse gas that plays an important role in global warming. Therefore, higher temperatures are not just a consequence of climate change but can also worsen cause of it, conclude climate researchers in an article published in Science.

During their research, the researchers made use of the methane concentrations determined by SRON Netherlands Institute for Space Research on the basis of measurements from the Dutch-German space instrument SCIAMACHY (on board ESA's environmental satellite Envisat).

The team of researchers -- from SRON and the University of Edinburgh -- investigated the methane emissions from the world's largest methane sources: paddy fields, marshes and bogs. These wetlands can be found in both the tropics and at higher altitudes and exhibit strong variations in their emissions.

The researchers discovered that fluctuations in the methane emissions in the tropics are mainly determined by variations in the groundwater level but that fluctuations in the methane emissions at high latitudes are mainly due to variations in the surface temperature. The team drew these conclusions based on satellite data about the earth's atmosphere (SCIAMACHY) and surface temperature for the period 2003-2007, and satellite measurements of variations in the gravitational field (GRACE) that were used to calculate variations in groundwater levels. An analysis of the data revealed that the total emission of the boggy areas increased by 7 percent during this period.

Future climate changes

In the Science article, the researchers describe which regional wetlands are sensitive to fluctuations in the groundwater level and which for extremely high temperatures, with the result that they emit more methane. This will help scientists to more accurately predict future climate changes.

The University of Edinburgh's Prof. Paul Palmer, who led the research, says: "The research results underline the fact that global warming is a complex process -- higher temperatures in turn speed up the warming process. Our research strengthens our conviction that satellites can accurately register changes in the emission of greenhouse gasses at specific locations on the earth. This makes it possible to accurately map the emission of greenhouse gases from a wide variety of natural and man-made sources."

Christiaan Frankenberg, SRON researcher at the time of the research and co-author of the article in Science, adds: "The great thing about this study is that it shows that by combining different types of satellite data, you can gain new insights into the processes that can influence our climate."