Recent methane trends derived from S5P/TROPOMI data

<p>Methane (CH₄) has a relatively long tropospheric lifetime and is consequently a well-mixed greenhouse gas. CH₄, released by several<br />types of human activity and natural processes, is one important driver of climate change. The global mean concentration of CH₄ has<br />increased by 156% between the beginning of the industrial revolution around 1750 and 2019, reaching roughly 1866 ppb in 2019 (IPCC).<br />The time dependence of this increase is not well understood. For example, it is not entirely clear why CH₄ growth rates reached record&#160;<br />high values in 2020 and 2021. Furthermore, the number of published growth rates (annual methane increases) is limited and includes data<br />from NOAA and the Copernicus Climate Change Service. Hence the rate of increase of CH₄ calculated from independent data sources are<br />valuable for cross-verification and in furthering our understanding of the methane cycle.<br />The TROPOMI instrument onboard the Sentinel-5P satellite provides daily CH₄ data with a spatial resolution of roughly 7x7 km&#178;<br />and global coverage. We analyze the TROPOMI CH₄ data with the goal of determining robust values of the annual methane increases (AMI)<br />for both global and zonally resolved data. For this we utilize a dynamic linear model approach to separate the underlying methane level,<br />the seasonal and short-term variations. The AMIs are defined as the difference in the underlying (i.e. fitted) methane level between<br />the first and last day of a year. In this contribution, we present first results for global and zonal TROPOMI AMIs for the years 2019-2022.<br />We compare the resulting global TROPOMI AMIs with data from NOAA and Copernicus and discuss the distribution of zonal AMIs for the given years.</p>