Emissions from energy fell by about 2 billion metric tons, or 5.8% in 2020, from the prior year. Such a plunge “is without precedent in human history — broadly speaking, this is the equivalent of removing all of the European Union’s emissions from the global total,” the authors wrote.

Both the U.S. and EU saw emissions fall by 10%, with the steepest reductions concentrated in March, April, and May. China was the only large economy that saw emissions increase, by 0.8% on an annual basis. Much of that rise came toward the end of the year. China’s emissions were 7% higher in December 2020 than they were in December 2019.

The category with the biggest drop in energy-use emissions was transportation, as workers quarantined and business slowed or halted. The decline in oil use contributed more than half of the overall total, with half of that coming from road traffic and another 35% from grounded airplanes.

The bright spots—there were some—came in the renewables space. Electricity generated from the sun and wind reached a record 20% of the mix  of global energy sources for the first time, and electric vehicles sold in record numbers.

While the world simultaneously struggles to both return to normal and cut emissions permanently, the IEA is concerned about a post-pandemic CO₂ gusher. The speed with which energy demand returned as pandemic restrictions lifted “underscores the risk that CO₂ emissions will increase significantly this year,” the IEA wrote. 

Scientists estimate that emissions would have to plummet by 10% for the year before scientists could detect the reduction in the CO₂ concentration of the atmosphere, which has risen every year for decades.