Methane data from 2002 to present derived from satellite observations

This dataset provides atmospheric CH₄ observations as derived from satellite radiances. It consists of two types of products each covering a different part of the atmosphere: (i) The average CH₄ mixing ratio of the entire atmosphere from the Earth’s surface to the top of the atmosphere. These column-averaged mixing ratio products are referred to as “XCH4” products. (ii) Mid-tropospheric (MT) CH₄ mixing ratio products. These products are referred to as "MTCH4" products. These products can be used to monitor the spatial distribution and temporal evolution of CH₄. This is important as CH₄ is after CO₂ the most important anthropogenic so-called greenhouse gas enhancing global warming and associated climate change. Methane has many natural and anthropogenic sources. CH₄ time series show an annual cycle, e.g., due seasonal wetland emissions. Currently atmospheric methane also shows and increasing trend. The dataset can be used for several climate related applications: It can be used in combination with appropriate modelling (e.g., inverse modelling) to obtain information on CH₄ emission sources, to assess the quality of climate models, to generate (e.g., forcing) input data as used by climate models, to determine the atmospheric CH₄ growth rate, etc.
The XCH4 and MTCH4 satellite-derived data products complement networks of surface observations. Typically, surface observations are more accurate, but they are also sparse whereas the satellite observations cover large parts of the world not observed from the ground. The XCH4 and MTCH4 datasets are generated by applying so called retrieval algorithms to satellite radiance measurements. The XCH4 products are based on measurements of reflected solar radiation in the short-wave near-infrared (SWIR) spectral region. These measurements are sensitive to CH₄ changes in the entire atmospheric vertical column down to the Earth surface. This implies that the observations are limited to essentially cloud-free conditions. Strict quality filtering is applied to the data products to achieve highest possible data quality. Whereas generation of the XCH4 products requires reflected solar radiation, i.e., daytime observation conditions, the MT products have been generated from radiance measurements in the thermal infrared (TIR) spectral region. These measurements can be conducted day and night and therefore have a much better spatio-temporal coverage compared to the XCH4 data. These measurements have maximum sensitivity for CH₄ variations in the mid-troposphere and only limited sensitivity to CH₄ changes near the ground. The two types of datasets are therefore highly complementary as they contain different information on atmospheric CH₄.
The dataset consists of 2 types of products:

column-averaged mixing ratios of CH₄, denoted XCH4
mid-tropospheric CH₄ columns, denoted MTCH4.

The XCH4 products are available as Level 2 (L2) products (satellite orbit tracks) and as Level 3 (L3) product (gridded). The XCH4 L2 products are available as individual sensor products (SCIAMACHY: WFMD and IMAP algorithms; GOSAT: OCFP, OCPR, SRFP and SRPR algorithms; GOSAT-2: SRFP and SRPR algorithms) and as a multi-sensor merged product (EMMA algorithm). The L3 XCH4 product is generated by gridding the corresponding EMMA Level 2 product and is provided in OBS4MIPS format. The IASI Level 2 products are generated with the NLIS algorithm. The IASI Level 3 products are generated by merging and gridding the corresponding Level 2 products and are available in OBS4MIPS format. The XCH4 L3 dataset will be updated on a yearly basis, with each update cycle adding a new data version for the entire period, up to one year behind real time. The MTCH4 L3 dataset will be updated every 6 months. The L2 data end in 2022.
This dataset is produced on behalf of C3S with the exception of the SCIAMACHY L2 products that were generated in the framework of the GHG-CCI project of the European Space Agency (ESA) Climate Change Initiative (CCI).