|Paper title||METHANE+ : combining SWIR and TIR measurements from space to disentangle sources and sinks of methane|
|Form of presentation||Poster|
The global growth rate of methane in the atmosphere shows large fluctuations, the explanation of which has been a major source of controversy in the scientific literature. The renewed methane increase after 2007 has been attributed to either natural or anthropogenic sources, with the latter either dominated by agricultural or fossil emissions. Interannual variability in the hydroxyl radical, the main atmospheric sink of methane, has also been proposed as the dominant driver of the temporary pause in the methane increase prior to 2007. The average of atmospheric methane over the past 5 years is the highest since its atmospheric measurements started in the mid 1980s, with record high growth in 2020 despite the pandemic. As a result, methane is by far the largest contributor to the departure of the path to the 2oC target. Again, the exact causes for this record high growth is up for discussion, where it is clear that also the role of OH needs to be considered.
This shows that atmospheric monitoring of methane is needed, but also that the current capabilities are still insufficient to provide conclusive answers about its global drivers. One of the ways to better address this is to try to better resolve the 3D distribution of methane in the atmosphere, realising that the sinks and sources have a different vertical distribution.
Methane has been measured successfully from space using both SWIR and TIR observations. Recently the TROPOMI instrument has made a huge step in SWIR observations from space, and IASI sensors have been providing TIR observations for over a decade now and will continue to do so. Inverse modeling trying to resolve global sources (and sometimes also sinks) using satellite data measurements have been done, mostly using the SWIR for methane. However, SWIR and TIR have a very different height sensitivity for methane in the atmosphere which in principle – combined - should provide us with a better-resolved 3D distribution of methane and thereby with a better handle on OH as well.
The ESA METHANE+ project aims at using both TROPOMI SWIR and IASI TIR measurements to better disentangle the sources and sink of methane. The project on one hand puts effort in improving the respective satellite data products, while on the other hand focuses on using both datasets in an inverse modeling framework. We will present an overview of the project.