Global background methane concentrations calculated in support of the HTAP3-OPNS exercise

This repository contains global average methane concentrations up to the year 2050 as calculated by EMEP MSC-W (MET Norway) in support of the HTAP3-OPNS exercise. The projections include a Maximum Feasible Technical Reduction (MTFR) and baseline (CLE, for Current Legislation) scenario, as described in more detail in the supporting emission-file repository (Klimont et al., 2025; https://zenodo.org/records/14748815). In addition, concentrations for a hybrid constructed "HILO" scenario are calculated. The HILO scenario combines air pollutant emissions (VOC, CO, NOx) from the MTFR scenario with methane emissions from the CLE scenario. For all three scenarios, greenhouse gases other than methane and pollutants other than VOC, CO, and NOx are taken from the SSP2-4.5 scenario.

The methane projections are calculated using the MAGICC7 model (Meinshausen et al., 2020, 2011, 2009) following the approach outlined in van Caspel et al. (2024). The MAGICC7 model is a probabilistic earth system model emulator, developed to efficiently calculate future greenhouse gas concentrations and global mean temperature change based on anthropogenic emission scenarios. The emission scenarios are combined with global averaged observed methane concentrations from the NOAA network (Lan et al., 2024) over a historical reference period (here taken to be 2018-2023) to estimate biogenic methane emissions. The biogenic emissions (estimated to amount to 205.7 Tg/yr) are kept fixed in the future projections, noting that the model also includes temperature-dependent permafrost emissions. The MAGICC7 model is further run in its 600-ensemble probabilistic mode, with the provided methane concentrations representing ensemble averages.

Each of the scenario files contain global average methane concentrations between the years 1990 and 2050, with years up to and including 2023 corresponding to observed concentrations. 

References:

Klimont, Z., Heyes, C., Hoglund-Isaksson, L., Lindl, F., Kim, Y., Rafaj, P., Purohit, P., Kaltenegger, K., Gomez-Sanabria, A., Winiwarter, W., Warnecke, L., Schoepp, W., Kiesewetter, G., Sander, R., Nguyen, B., Zhang, S., Brocza, F., & Wagner, F. (2025). Global gridded anthropogenic emissions of air pollutants and methane for the period 1990-2050 (V2.1) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.14748815

van Caspel, W. E., Klimont, Z., Heyes, C., and Fagerli, H.: Impact of methane and other precursor emission reductions on surface ozone in Europe: scenario analysis using the European Monitoring and Evaluation Programme (EMEP) Meteorological Synthesizing Centre – West (MSC-W) model, Atmos. Chem. Phys., 24, 11545–11563, https://doi.org/10.5194/acp-24-11545-2024, 2024. 

Lan, X., Thoning, K., and Dlugokencky, E.: Trends in globally-averaged CH4 , N2 O, and SF6 determined from NOAA Global Monitoring Laboratory measurements, Version 2024-07, https://doi.org/10.15138/P8XG-AA10, 2024.

Meinshausen, M., Meinshausen, N., Hare, W., Raper, S. C., Frieler, K., Knutti, R., Frame, D. J., and Allen, M. R.: Greenhouse-gas emission targets for limiting global warming to 2 C, Nature, 458, 1158–1162, https://doi.org/10.1038/nature08017, 2009.

Meinshausen, M., Raper, S. C. B., and Wigley, T. M. L.: Emulating coupled atmosphere-ocean and carbon cycle models with a simpler model, MAGICC6 – Part 1: Model description and calibration, Atmos. Chem. Phys., 11, 1417–1456, https://doi.org/10.5194/acp-11-1417-2011, 2011.

Meinshausen, M., Nicholls, Z. R. J., Lewis, J., Gidden, M. J., Vogel, E., Freund, M., Beyerle, U., Gessner, C., Nauels, A., Bauer, N., Canadell, J. G., Daniel, J. S., John, A., Krummel, P. B., Luderer, G., Meinshausen, N., Montzka, S. A., Rayner, P. J., Reimann, S., Smith, S. J., van den Berg, M., Velders, G. J. M., Vollmer, M. K., and Wang, R. H. J.: The shared socio-economic pathway (SSP) greenhouse gas concentrations and their extensions to 2500, Geosci. Model Dev., 13, 3571–3605, https://doi.org/10.5194/gmd-13-3571-2020, 2020.