Southeast Australia experienced intensive and geographically extensive wildfires during the 2019–2020 summer season1,2. The fires released substantial amounts of carbon dioxide into the atmosphere3. However, existing emission estimates based on fire inventories are uncertain4, and vary by up to a factor of four for this event. Here we constrain emission estimates with the help of satellite observations of carbon monoxide5, an analytical Bayesian inversion6 and observed ratios between emitted carbon dioxide and carbon monoxide7. We estimate emissions of carbon dioxide to be 715 teragrams (range 517–867) from November 2019 to January 2020. This is more than twice the estimate derived by five different fire inventories8–12, and broadly consistent with estimates based on a bottom-up bootstrap analysis of this fire episode13. Although fires occur regularly in the savannas in northern Australia, the recent episodes were extremely large in scale and intensity, burning unusually large areas of eucalyptus forest in the southeast13. The fires were driven partly by climate change14,15, making better-constrained emission estimates particularly important. This is because the build-up of atmospheric carbon dioxide may become increasingly dependent on fire-driven climate–carbon feedbacks, as highlighted by this event16.
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Acknowledgements We thank the team that realized the TROPOMI instrument, comprising a partnership between Airbus Defence and Space Netherlands, the Royal Netherlands Meteorological Institute (KNMI), the SRON Netherlands Institute for Space Research and the Netherlands Organisation for Applied Scientific Research (TNO), commissioned by the Netherlands Space Office (NSO) and the European Space Agency (ESA). The Sentinel-5 Precursor is part of the European Union (EU) Copernicus programme, and Copernicus Sentinel data from 2019 and 2020 have been used here. The WRF model computations were carried out on the Dutch national e-infrastructure with the support of the SURF Cooperative. We also thank the large team of scientists and technicians who worked on the fire emission data sets available online. G.R.v.d.W. and I.R.v.d.V. are partly supported by the Netherlands Organization for Scientific Research (NWO; VICI research programme 016.160.324).
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