Investigating the atmospheric composition and climate response to mitigation: a methane emissions-driven approach
type: CreativeWork
description: Methane is the second most important greenhouse gas after carbon dioxide, and also plays a central role in the chemistry of the atmosphere. The combination of its shorter lifetime and higher effectiveness as a greenhouse gas makes it an attractive option for near-term mitigation of climate change. Methane is also a key tropospheric ozone precursor: ozone is a greenhouse gas, and acts as an air pollutant in the troposphere. Therefore, mitigation of methane has both climate and air quality benefits. A new configuration of the UK Earth System Model, UKESM1-ems, has been developed with an updated methane treatment. Methane emissions are input directly, rather than prescribing a global surface concentration. This thesis focuses on UKESM1-ems and the new capabilities it provides: a more process-based treatment of methane; simulating feedbacks in the methane cycle, and the ability to directly perturb methane emissions. When compared to the previous, concentration-driven model, UKESM1-ems simulates the methane distribution with a better correlation compared to observations, including an improved latitudinal distribution, interhemispheric gradient and vertical gradient. The observed trend in methane over time is also reproduced, combining the methane emissions inputs, online wetland emissions and online chemistry and transport to simulate the methane mixing ratio. The modelled absolute methane mixing ratio is lower than observations: this is likely due to an underestimate in methane emissions, within the current large uncertainty range for emissions. Experiments following different emissions pathways are explored using UKESM1-ems. Firstly, an idealised scenario where all anthropogenic methane emissions are removed instantaneously, to attribute the role of future anthropogenic methane. Methane declines to below pre-industrial levels within 12 years and global surface ozone decreases to levels seen in the 1970s. By 2050, 690,000 premature deaths per year and 1 degree of warmin…
abstract: Methane is the second most important greenhouse gas after carbon dioxide, and also plays a central role in the chemistry of the atmosphere. The combination of its shorter lifetime and higher effectiveness as a greenhouse gas makes it an attractive option for near-term mitigation of climate change. Methane is also a key tropospheric ozone precursor: ozone is a greenhouse gas, and acts as an air pollutant in the troposphere. Therefore, mitigation of methane has both climate and air quality benefits. A new configuration of the UK Earth System Model, UKESM1-ems, has been developed with an updated methane treatment. Methane emissions are input directly, rather than prescribing a global surface concentration. This thesis focuses on UKESM1-ems and the new capabilities it provides: a more process-based treatment of methane; simulating feedbacks in the methane cycle, and the ability to directly perturb methane emissions. When compared to the previous, concentration-driven model, UKESM1-ems simulates the methane distribution with a better correlation compared to observations, including an improved latitudinal distribution, interhemispheric gradient and vertical gradient. The observed trend in methane over time is also reproduced, combining the methane emissions inputs, online wetland emissions and online chemistry and transport to simulate the methane mixing ratio. The modelled absolute methane mixing ratio is lower than observations: this is likely due to an underestimate in methane emissions, within the current large uncertainty range for emissions. Experiments following different emissions pathways are explored using UKESM1-ems. Firstly, an idealised scenario where all anthropogenic methane emissions are removed instantaneously, to attribute the role of future anthropogenic methane. Methane declines to below pre-industrial levels within 12 years and global surface ozone decreases to levels seen in the 1970s. By 2050, 690,000 premature deaths per year and 1 degree of warmin…
author: Staniaszek, Zofia
language: eng
keywords: air quality, atmospheric chemistry, chemistry-climate modelling, climate, emissions-driven, methane, methane mitigation
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/83f1f9b2-99ed-4dbc-9681-ead8404eb307/download
license: https://creativecommons.org/licenses/by-nc/4.0/
date published: 2023-08
date modified: 2026-07-22T22:24:27Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.106388