Australian wildfires boost forecast 2020 carbon dioxide rise

Concentrations of carbon dioxide in the atmosphere are expected to experience the largest annual rise since measurements began in 1958. The bushfires in Australia are partly responsible.

Australia's fires are expected to add to atmospheric CO2
Australia's fires are expected to add to atmospheric CO2

Australia’s bushfires will contribute more to the annual carbon dioxide (CO2) rise than the increase in emissions caused by humans between 2018 and 2019, scientists have predicted.

Atmospheric concentrations of carbon dioxide are measured at Mauna Loa in Hawaii. They are expressed in parts per million (ppm). Climate scientists say the world needs to keep atmospheric CO2 under 450ppm in order to stop climate change passing dangerous levels.

Scientists at the Met Office have predicted that 2020 will witness one of the largest annual rises in concentration since records began 60 years ago.

Weaker absorption of CO2

Atmospheric CO2 is expected to peak in May, at about 417ppm, while the average for the year is estimated at 414ppm, some 2.74ppm above the average for 2019.

Emissions from humans burning fossil fuels and cutting down forests have driven increases in atmospheric CO2 every year since 1958. The rate of the rise is not always even, due to the amount of carbon absorbed by ecosystems such as tropical forests.

However, the rate at which ecosystems absorb carbon is expected to be weaker than normal for the second year running, meaning that atmospheric carbon will rise by around 10% this year. Emissions from the Australian bushfires will contribute up to one-fifth of this surge, scientists believe.

Recovery uncertain

If ecosystems in Australia fully regrow to the same size as before the fires, the emissions from the fires could be considered temporary, the scientists said.

However, it is possible that the widespread impact of the fires and potential changes to the way they are managed might result in new ecosystems, with smaller amounts of organic material available to absorb carbon.

If predictions for this year’s atmospheric CO2 become reality, it will be the fourth largest rise on record. The largest on record was 2016, due to a major contribution from that year’s El Niño - a band of warm ocean water in the Pacific which has a significant impact on the weather, particularly in Latin America.

The second largest rise in atmospheric CO2 was in 2019, which was closely followed by 1998. There was a major El Niño in 1997/98, though only a minor one in 2019. Annual increments of atmospheric CO2 have generally been increasing over time as a result of rising anthropogenic (human induced) emissions.