In a recent study, published in Nature Communications, scientists from the National Centre for Earth Observation (NCEO) used satellite observations of atmospheric methane to infer maps of methane emissions. They found that methane emissions from tropical wetlands represented about 60% of the global methane annual total and explained a large portion (up to 80%) of year-to-year variations of its annual growth rate.
The research team also found strong correlations between tropical sea surface temperature (SST) anomalies and variations in terrestrial methane emissions (via changes in rainfall and temperature), which could form the basis of a future climate feedback mechanism as climate model projections suggest these SST anomalies will become more extreme.
Professor Paul Palmer, Director of Strategic Science, NCEO, said:
‘This study helps to reveal how interconnected parts of the natural world are responding to changes in climate. It has only been possible by having a self-consistent decadal record of atmospheric methane developed by Japanese and NCEO researchers.’
There are still large gaps in the current global methane budget and scientists from NCEO are applying observations and numerical analysis to improve our quantifications of natural and anthropogenic emissions. Emissions of methane from tropical wetlands represent a significant fraction of global methane budget so it is important to understand their magnitude and the processes that control their variation.
Importance of methane as a greenhouse gas
Methane (CH4) is the second most important greenhouse gas in the atmosphere after carbon dioxide (CO2). Since the pre-industrial era, methane concentration in atmosphere has more than doubled, contributing about a third of current human-induced global warming.
It is therefore critical to implement policies aimed at reducing methane emissions as a key to combating climate change. At COP26 in Glasgow, more than 100 countries signed a pledge to reduce methane gas emissions by 30% in less than ten years. This is a critical step in keeping global warming to 1.5°C when compared with pre-industrial levels.
Scientists have been monitoring global methane levels for decades. Recent space-borne and surface-based observations confirms that after nearly a decade of pause, atmospheric methane concentrations started to increase again since 2007. Yet its causes, as well as its future trends, are not yet fully understood.
Read the full paper: Tropical methane emissions explain large fraction of recent changes in global atmospheric methane growth rate in Nature Communications.
About the author
Contact Dr Liang Feng for further information
National Centre for Earth Observation and School of GeoSciences, University of Edinburgh