ANSTO Scientists Refine Global Methane Estimates

A groundbreaking international study published in the Journal of Geophysical Research: Atmospheres has provided new insights into global fossil methane emissions, using innovative multi-isotopic atmospheric measurements.

Principal Accelerator Scientist Dr Andrew Smith, a co-author who has investigated methane emissions for over two decades with A/Prof Vasilii Petrenko and others, contributed significantly to this collaborative research, which has improved the accuracy of greenhouse gas emission estimates and support more effective global climate mitigation efforts.

The study, led by Dr Ryo Fujita of the Imperial College London and the Japanese Meteorological Research Institute in Tsukuba, used advanced isotopic analysis, including radiocarbon and stable isotopes of carbon and hydrogen, to accurately distinguish between different methane emission sources. This research is the first research to integrate multiple isotopic datasets to precisely quantify global methane emissions from fossil fuels, biogenic, geologic, and biomass burning sources across the historical timeframe from 1750 to 2015.

One key finding of the study was that global fossil methane emissions are about 130 teragrams per year for the period 2003-2012, which closely matches the Global Carbon Project estimates, a network of scientists and institutions investigating greenhouse gases. To put this into perspective, a teragram is one trillion grams, approximately equivalent to the mass of water in 400 Olympic-sized swimming pools.

Importantly, the study contradicts earlier claims of significantly underestimated fossil methane emissions, bringing clarity to previously conflicting scientific assessments.

Dr. Smith highlighted the importance of multi-isotopic measurements for resolving uncertainties in methane emission inventories. "This study demonstrates that combining multiple isotopic constraints significantly reduces uncertainties in methane emission estimates. Such precise data are crucial for effective climate policy and mitigation strategies," he said.

ANSTO's Centre for Accelerator Science, a world leader in extracting and accurately measuring radiocarbon from minuscule carbon samples. This intricate process requires the identification and counting of individual atoms through accelerator mass spectrometry.

David Child, Leader of the Chemistry Group, Centre for Accelerator Science emphasised the exacting preparation required for these measurements: "Our analytical processes demand incredible precision in the handling and careful chemical purification of tiny samples, essential for answering the most challenging environmental research questions of our times".

Dr Bin Yang carried out the demanding graphitisation process, transforming CO₂ from ice cores into graphite targets for accelerator measurements.

Dr Andrew Smith participated in polar sampling expeditions and performed the radiocarbon measurements using the atom counting technique of accelerator mass spectrometry in the Centre for Accelerator Science at ANSTO.

These results highlight the need for continued international collaboration in tracking greenhouse gas emissions and the importance of ongoing research to support accurate climate policy. ANSTO remains pivotal in global efforts, leveraging nuclear science to tackle environmental challenges.

Other contributing organisations included Ricerca sul Sistema Energetico (Italy), University of Rochester, University of Colorado Boulder (US), and Tohoku University (Japan).