Daily global CO2 emissions fell 17% at the height of the shutdown due to government action in response to Covid-19, scientists say.
The most comprehensive report ever published indicates that almost half of the record decline is due to fewer car trips.
But the authors are concerned that as people get back to work, car use will increase again.
They fear that CO2 emissions will soon be higher than before the crisis.
They urge politicians to seize the moment and make real and lasting changes to transportation and personal mobility.
In the UK, Transport Secretary Grant Shapps has pledged £ 250 million to improve cycling and walking infrastructure. Other countries are also considering similar plans.
The restrictions that most governments put in place in response to Covid-19 have had a significant impact on carbon production activities which are integrated into almost everything we do.
Road transport has declined enormously, as has aviation.
However, now that the UK is starting to return to work, Mr Shapps said people should drive to work rather than using public transport, if walking or cycling is not an option.
“If you cannot walk or cycle but have access to a car, please use it rather than traveling by bus, train or tram,” he said.
The industry temporarily closed and demand for energy around the world has collapsed.
Now, in a detailed analysis, the researchers have shown how these changes have had an impact on our CO2 emissions.
They calculated the reduction in carbon on the basis of the locking policies implemented in 69 countries which together account for 97% of global emissions.
At the height of the crisis in early April, daily emissions fell 17% from the previous year, which means that around 17 million tonnes less CO2 were emitted every day.
The key to the fall was cars. Emissions from surface transportation decreased by 43%, the same amount as the decline in industry and power generation combined.
While the aviation slowdown has made the headlines for the economic impact, it only accounts for 10% of the decline during the pandemic.
China posted the largest decline, followed by the United States, Europe and India.
If certain restrictions on economic activity remain in place around the world until the end of the year, global emissions are likely to decrease by 7%.
If transportation and economic activity levels prior to the pandemic returned in mid-June, the annual decline would be approximately 4%.
But the research team that carried out this work is concerned that the rebound, especially on the roads, will experience a carbon boost.
Analysis – Roger Harrabin, environmental analyst
The lockout also raised questions about other pollutants. One of the UK’s leading experts, Professor Frank Kelly of London’s King’s College, said he knew that diesel cars were emitting far more pollution than expected – two years before U.S. officials disclosed the scandal.
He told Radio 4’s The Life Scientific that his team discovered a huge disconnect between the emissions reported by the automakers and the actual readings on the road.
Professor Kelly said he reported it to the Ministry of the Environment, Food and Rural Affairs (Defra), but did not publish his findings. He said work subsequently undertaken in the United States has led to lawsuits against automakers who had installed “defeat devices” to deceive regulators.
The government has not denied the account. A spokesperson said, “We are taking urgent action to improve air quality and our clean air strategy has been hailed by the World Health Organization as an” example for the rest of the world “”.
Meanwhile, on the Covid-19 crisis, he said that levels of pollutant NO2 had dropped by up to 60% in London since the drop in traffic under control.
The levels of another pollutant, soot particles, remained at harmful levels.
“A big concern that people will naturally want to get back into their cars to go to work, and this could cause emissions to rebound to the same level or even more than before, once everyone is back,” said Professor Corinne The Quéré of the University of East Anglia, who directed the analysis.
Researchers say that fundamental and systemic change is necessary if the emissions curve is to be flattened to limit the worst impacts of climate change.
In terms of transportation, the opportunities are enormous, according to Professor Le Quéré.
She says that after the global financial crisis of 2008, some governments like China, the United States and Germany made significant investments in wind and solar power, which brought down the prices of these renewable energies .
“Here in 2020, we are very close to the same situation with regard to electric mobility,” she told BBC News.
“Battery prices have gone down, we have a lot of models and governments will try to boost their savings. “
“So if these two things can line up, it could make a huge difference to tomorrow’s transportation. “
Seizing the opportunity presented by the virus is also at the forefront of business thinking on climate change.
A letter signed by 155 large companies, representing $ 2.4 trillion (£ 1.96 trillion) in market capitalization, calls for a net zero emissions response to the lust crisis.
Companies such as Carlsberg, Iberdrola, EDF and Coca Cola Europe say they want governments to “favor a faster and fairer transition from a gray economy to a green economy”.
The authors of the latest carbon analysis agree that the time has come to act. They point out that if CO2 emissions can be temporarily reduced, then CO2 concentrations persist in the atmosphere, warming the planet.
It will take a radical change to change that.
“I very much think that we are at a crossroads. And at this point, as British Prime Minister Boris Johnson has said, it could go both ways. “
“He was talking about his own health, but here we are talking about the health of the planet. “
“It could go both ways. “
The study was published in the journal Nature Climate Change.
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