The global COVID-19 lockdowns caused fossil carbon dioxide emissions to decline by an estimated 2.4 billion tonnes in 2020 – a record drop according to researchers at Future Earth’s Global Carbon Project.

The fall is considerably larger than previous significant decreases ­– 0.5 (in 1981 and 2009), 0.7 (1992), and 0.9 (1945) billion tonnes of CO2 (GtCO2). It means that in 2020 fossil CO2 emissions are predicted to be approximately 34 GtCO2, 7% lower than in 2019.

Emissions from transport account for the largest share of the global decrease. Those from surface transport, such as car journeys, fell by approximately half at the peak of the COVID-19 lockdowns. By December 2020, emissions from road transport and aviation were still below their 2019 levels, by approximately 10% and 40%, respectively, due to continuing restrictions. Total CO2 emissions from human activities – from fossil CO2 and land-use change – are set to be around 39 GtCO2in 2020.

The release of this year’s Global Carbon Budget comes ahead of the fifth anniversary tomorrow of the adoption of the UN Paris climate Agreement, which aims to reduce the emission of greenhouse gases to limit global warming. Cuts of around 1 to 2 GtCO2 are needed each year on average between 2020 and 2030 to limit climate change in line with its goals.

Five years on from the landmark agreement, the international team behind the annual carbon update say growth in global CO2 emissions had begun to falter, with emissions increasing more slowly in recent years, which could be partly in response to the spread of climate policy. For the decade prior to 2020, fossil CO2 emissions decreased significantly in 24 countries while their economy continued to grow.

However, the researchers warn that it is too early to say how much emissions will rebound by during 2021 and beyond, as the long-term trend in global fossil emissions will be largely influenced by actions to stimulate the global economy in response to the COVID-19 pandemic.

Prof Corinne Le Quéré, Royal Society Research Professor at UEA’s School of Environmental Sciences, contributed to this year’s analysis. She said: “All elements are not yet in place for sustained decreases in global emission, and emissions are slowly edging back to 2019 levels. Government actions to stimulate the economy at the end of the COVID-19 pandemic can also help lower emissions and tackle climate change.

“Incentives that help accelerate the deployment of electric cars and renewable energy and support walking and cycling in cities are particularly timely given the extensive disturbance observed in the transport sector this year.”

The emissions decrease appears more pronounced in the US (–12%) and EU27 countries (– 11%), where COVID-19 restrictions accelerated previous reductions in emissions from coal use.  It appears least pronounced in China (–1.7%), where the effect of COVID-19 restrictions on emissions occurred on top of rising emissions. In addition, restrictions in China occurred early in the year and were more limited in their duration, giving the economy more time to recover.

In the UK, which first introduced lockdown measures in March, emissions are projected to decrease about 13%. The large decrease in UK emissions is due to the extensive lockdown restrictions and the second wave of the pandemic.

In India, where fossil CO2 emissions are projected to decrease about 9%, emissions were already lower than normal in late 2019 because of economic turmoil and strong hydropower generation, and the COVID-19 effect is potentially superimposed on this changing trend.

For the rest of the world the effect of COVID-19 restrictions occurred on top of rising emissions, with emissions this year projected to decrease by about 7%.

Globally, the peak of the decrease in emissions in 2020 occurred in the first half of April, when lockdown measures were at their maximum, particularly across Europe and the USA.

Emissions from industry, for example metal production, chemicals, and manufacturing, reduced by up to a third during the COVID-19 lockdown in spring. However, they could already be back up to near or even above 2019 levels by now.

Despite lower emissions in 2020, the level of CO2 in the atmosphere continues to grow – by about 2.5 parts per million (ppm) in 2020 – and is projected to reach 412 ppm averaged over the year, 48% above pre-industrial levels.

Lead researcher Prof Pierre Friedlingstein, of the University of Exeter, said: “Although global emissions were not as high as last year, they still amounted to about 39 billion tonnes of CO2, and inevitably led to a further increase in CO2 in the atmosphere. The atmospheric CO2 level, and consequently, the world’s climate, will only stabilize when global CO2 emissions are near zero.”

Preliminary estimates based on fire emissions in deforestation areas indicate that emissions from deforestation and other land-use change for 2020 are similar to the previous decade, at around 6 GtCO2. Approximately 16 GtCO2 was released, primarily from deforestation, while the uptake of CO2 from regrowth on managed land, mainly after agricultural abandonment, was just under 11 GtCO2. Measures to better manage land could both halt deforestation and help increase the CO2 sink from regrowth.

Deforestation fires were lower this year compared to 2019 levels, which saw the highest rates of deforestation in the Amazon since 2008. In 2019 deforestation and degradation fires were about 30% above the previous decade, while other tropical emissions, mainly from Indonesia, were twice as large as the previous decade because unusually dry conditions promoted peat burning and deforestation.

Land and ocean carbon sinks continue to increase in line with emissions, absorbing about 54% of the total human-induced emissions.

Data for the Global Carbon Budget 2020 is published today in the journal Earth System Science Data.