Future CH4 as modelled by a fully coupled Earth system model: prescribed GHG concentrations vs. interactive CH4 sources and sinks
We have used the NASA Goddard Institute for Space Studies (GISS) Earth system model GISS-E2.1 to study the future budgets and trends of global and regional CH _4 under different emission scenarios, using both the prescribed GHG concentrations as well as the interactive CH _4 sources and sinks setup...
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| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
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| Series: | Environmental Research: Climate |
| Subjects: | |
| Online Access: | https://doi.org/10.1088/2752-5295/adb3c0 |
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| Summary: | We have used the NASA Goddard Institute for Space Studies (GISS) Earth system model GISS-E2.1 to study the future budgets and trends of global and regional CH _4 under different emission scenarios, using both the prescribed GHG concentrations as well as the interactive CH _4 sources and sinks setup of the model, to quantify the model performance and its sensitivity to CH _4 sources and sinks. We have used the Current Legislation (CLE) and the maximum feasible reduction (MFR) emission scenarios from the ECLIPSE V6b emission database to simulate the future evolution of CH _4 sources, sinks, and levels from 2015 to 2050. Results show that the prescribed GHG version underestimates the observed surface CH _4 concentrations during the period between 1995 and 2023 by 1%, with the largest underestimations over the continental emission regions, while the interactive simulation underestimates the observations by 2%, with the biases largest over oceans and smaller over the continents. For the future, the MFR scenario simulates lower global surface CH _4 concentrations and burdens compared to the CLE scenario, however in both cases, global surface CH _4 and burden continue to increase through 2050 compared to present day. In addition, the interactive simulation calculates slightly larger O _3 and OH mixing ratios, in particular over the northern hemisphere, leading to slightly decreased CH _4 lifetime in the present day. The CH _4 forcing is projected to increase in both scenarios, in particular in the CLE scenario, from 0.53 W m ^−2 in the present day to 0.73 W m ^−2 in 2050. In addition, the interactive simulations estimate slightly higher tropospheric O _3 forcing compared to prescribed simulations, due to slightly higher O _3 mixing ratios simulated by the interactive models. While in the CLE, tropospheric O _3 forcing continues to increase, the MFR scenario leads to a decrease in tropospheric O _3 forcing, leading to a climate benefit. Our results highlight that in the interactive models, the response of concentrations are not necessarily linear with the changes in emissions as the chemistry is non-linear, and dependent on the oxidative capacity of the atmosphere. Therefore, it is important to have the CH _4 sources and chemical sinks to be represented comprehensively in climate models. |
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| ISSN: | 2752-5295 |