Abstract:
Methane was discovered 250 years ago by Alessandro Volta in 1776, but its atmospheric budget is still not understood. There is evidence for a strong rise in wetland, agricultural and waste emissions, especially natural emissions from regions in tropical Africa such as South Sudan’s Sudd wetland, as well as in the boreal/Arctic realm. 14CO data suggest an increasing OH sink since 1997, implying the rise in methane emissions was even stronger than previously thought. Following more than a decade of strong growth, 2020-2022 brought a major surprise: the highest growth in the observational record. The causes of the surge seem to include a transient decline in the oxidative power of the atmosphere, coupled with rising wetland emissions. The implications are profound: it’s going to be very hard to bring methane’s growth under control.
Growth in emissions from wetlands and tropical agriculture makes the Global Methane Pledge’s goal of cutting the total atmospheric methane burden harder to achieve. However, there are many easy wins – coal mine vents in China and India, livestock manure, landfills, sewage and biomass fires. In Africa and India landfill management is very poor and rural crop waste burning is widespread, despite the damaging impact of air pollution on public health: much can be done here. In the dairy industry of Europe, the US, China and temperate Southern Hemisphere emission mitigation is increasingly feasible. Overall, meeting the targets of the Global Methane Pledge looks very difficult: but there’s hope that much can change, especially in China.
Biography:
Euan Nisbet is emeritus professor of Earth Sciences, at Royal Holloway, Univ. of London. After studying at Univ. Zimbabwe and at Sidney Sussex college, his geology PhD was in Darwin College, After a NERC Independent fellowship in Oxford and a Royal Society postdoc in ETH Zurich, he joined the staff of Mineralogy and Petrology in Cambridge, prior to the merger into Earth Sciences. For many years he and CMR Fowler, his wife, both taught in the Earth Sciences Dept., Univ. of Saskatchewan (he has prairie ancestry). He led the Canadian Lithosphere Committee for many years, advising the government on natural hazards, including methane hydrate. From 1985-7 he held a Steacie Fellowship from the Governor-General which, with help from Paul Crutzen and Ralph Cicerone, prompted a switch from hard rock geology to atmospheric methane, much to the annoyance of the funding agency who halved his grant. At Royal Holloway he led or co-led many large European consortia, such as Meth-MoniEUr, the West European Methane Budget experiment, EuroHydros, Geomon, MEMO etc. etc. and many NERC projects, including the UK MOYA Global Methane Budget consortium (2016-2022). Many projects were in collaboration with John Pyle. Now retired, he serves on the scientific advisory panel for the United Nations International Methane Emissions Observatory. His input was used in the 2021 Global Methane Assessment underpinning the Global Methane Pledge, and he is a co-author of the 2025 UNEP Global Methane Status report.
