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Corona-induced carbon reductions still undetectable in the atmosphere

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While global carbon emissions have fallen since the beginning of the coronavirus pandemic, scientists have found that this reduction is not yet being reflected in atmospheric concentrations of carbon dioxide.

Current estimates suggest that global restrictions on industry, transport and socialising should lead to a reduction in carbon emissions of up to eight per cent this year, possibly the largest fall since World War 2.

“In spite of the reduced emissions, our measurements show that CO2 concentration in the atmosphere has not yet decreased,” said Ralf Sussmann from the Karlsruhe Institute of Technology in Germany.

“To reduce CO2 concentration in the atmosphere in the long run, restrictions imposed during the corona pandemic would have to be continued for decades. But even this would be far from being sufficient.”

For the study, the researchers used data from the Total Carbon Column Observing Network (TCCON). It measured the concentrations in different layers of the atmosphere in several places around the globe using high-tech infrared spectrometers, which use the Sun as a light source.

“This measurement method is highly precise; uncertainties are in the range of a few thousandths,” Sussmann said.

Due to the long life of CO2 and the high background concentrations that have accumulated since the start of industrialisation, changes in the atmosphere are so far undetectable.

“Also, natural impacts make early detection difficult. Anthropogenic emissions, the main cause of the long-term increase in atmospheric CO2, are superposed by annual fluctuations of the growth rate due to natural climate variabilities of ocean sinks and land vegetation,” Sussmann said.

The researchers compared the TCCON measurements with the expected atmospheric growth rate for 2020 – with and without corona restrictions.

“Precision analysis of atmosphere measurements revealed that the impacts of Covid-19 measures on the atmosphere might be measured after little more than six months,” he added. “In any case, we would be able to find out within presumably two and half years, whether global political and social measures will help us find viable alternatives of fossil fuels and reach the goals of the Paris Climate Agreement.”

According to the Intergovernmental Panel on Climate Change, cumulative reductions of carbon on the order seen this year would be required every year to reach the goals of the Paris Agreement by 2030.

“The restrictions imposed during the corona crisis are far from being sufficient. They have just resulted in a one-time reduction by eight percent. Political measures have to be taken to directly initiate fundamental technological changes in the energy and transport sectors,” Sussmann said.

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