The study, which drew on data from 69 countries including Australia, cited a grounded aviation industry and a lack of cars on the road as the key reasons for the decline.

Twitter : Pep Canadell

@pepcanadell

Global daily emissions of fossil CO2 dropped by 17% due to Covid-19

Without the existence of real-time monitoring of CO2, scientists used policies to predict how much global emissions reduced by between 1 January and 30 April.

On 7 April alone, the study said emissions were 17 per cent lower than they were on the same day last year - the largest change during the analysed period.

"To put that figure in context, daily emissions declined on average between January to April by 8.6 per cent again compared to the same period last year," CSIRO researcher and Global Carbon Project Director Dr Pep Canadell said

"The peak 17 per cent daily decline on 7 April was because China, the US, India, and all other major carbon-emitting countries were all in a high-level of lock-down at the same time."

Dr Canadell, who is also a co-author of the study, said the decreases in emissions were largest in China, where industry and communities were first locked down, followed by the US, Europe and India.

While transport, industry and public building emissions trended lower, home emissions were on the rise. 

"With people being urged to stay home and isolate, there was a corresponding increase in global residential emissions of 2.8 per cent, which saw a 0.2 megatonne increase in CO2 at its peak decline," Dr Canadell said. 

Before the coronavirus, the scientists said global emissions were rising by about 1 per cent per year over the past decade, with the exception of 2019, which saw no growth.

Overall emissions for 2020 will be dependent on how long restrictions remain in place around the world.

If countries remain in lockdowns of varying levels until the end of the year, the study predicted an overall decrease in carbon emissions of 7.5 per cent.

If restrictions are largely lifted by mid-June, that reduction would shrink to 4.2 per cent.

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