The concentration of carbon dioxide in the atmosphere is what matters when it comes to climate change – and the UK’s Met Office is forecasting a near-record increase in 2020. The yearly increase in CO2 may be 2 per cent higher than it would be otherwise because of wildfires that have been burning for months in Australia.
These fires are estimated to have emitted between 0.4 and 0.7 gigatonnes of CO2, says Richard Betts at the Met Office. That’s a huge amount, though not as much as the fires in Indonesia in 1998, which may have produced between 3 and 9 gigatonnes.
Before the industrial age began, levels of CO2 in the atmosphere were around 280 parts per million (ppm). When Charles Keeling began measuring them at Mauna Loa in Hawaii in the 1950s, they were around 315 ppm and increasing by less than 1 ppm per year.
In 2019, the average level at Mauna Loa was 411.5 ppm, and during the past decade levels have been rising by more than 2 ppm per year on average.
Betts and his colleagues forecast that in 2020, the average level at Mauna Loa will rise to 414.2 ppm. He began forecasting the yearly increase in CO2 in 2016, and so far his team’s forecasts have been accurate.
CO2 levels are rising because of the 37 gigatonnes of CO2 from fossil fuels now emitted every year. However, only half the CO2 we emit remains in the atmosphere. The rest is taken up by the oceans and by plants on land. The annual CO2 increase therefore varies greatly depending on global weather patterns that affect plant growth.
The Pacific ocean is expected to be extra warm in 2020, leading to warmer and drier weather over many land areas that should result in 10 per cent more CO2 than usual staying in the atmosphere. A fifth of that extra 10 per cent will be due to the Australian wildfires alone.
Higher annual rises in CO2 have only happened in 1998, 2015, 2016 and 2018. Most were El Niño years, when warm surface waters spread across the Pacific. Now the planet has warmed so much that big increases are occurring even in the absence of El Niños.
“Our forecast of the CO2 rise this year is almost as large as that in 1998 because although there is no large El Niño event like there was then, emissions have risen in the meantime,” says Betts.
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