The world’s carbon dioxide emissions saw their largest-ever one-year drop in 2020, falling 7% from 2019 to 34 billion metric tons because of pandemic-related restrictions. But in a new study, researchers said the world should be reducing its output at a rate only slightly less rapid for the rest of the decade, if it is to adhere to the Paris Agreement and avoid the worst effects of climate change.

For the paper published Wednesday in Nature Climate Change, scientists analyzed national and global emissions trends since the landmark climate accord became official in 2016 and found that even the 64 nations reducing their emissions are moving too slowly, with a cumulative average decline of 160 million tons per year before the pandemic. Setting aside the remaining countries with increasing emissions, the world should be cutting the greenhouse gas 10 times faster, they said.

For more than a year, most countries have adopted lockdowns and other disruptive policies to limit the novel coronavirus’ rapid spread. The resulting economic slowdown and reduced travel put a dent in many forms of pollution, including planet-warming carbon dioxide.

Based on data from the Global Carbon Project’s 2020 carbon budget released in December, the researchers found that countries’ carbon-dioxide emissions fell that year by a total of 2.6 billion metric tons, reaching 2010 and 2011 levels. Emissions decreased by 27% on average during the peak of pandemic confinement, and the transport sector played the largest role in reducing emissions throughout the year, according to the study.

In 2016, 194 countries signed the Paris climate accord in a pledge to keep global warming within 1.5 to 2 degrees Celsius above pre-industrial levels. Carbon dioxide emissions had been rising since then, before they nearly stagnated in 2019 at an all-time high of 36.8 billion tons. During this time period, the 36 “high-income” countries decreased their emissions by just 0.8% per year on average before emissions fell 9% in 2020, according to the paper. The other two income groups produced more of the greenhouse gas over the same time span and saw somewhat similar reductions last year.

The 7% decline was equivalent to the annual emissions of India, the world’s fourth-biggest emitter, but much more progress must be made to adhere to the Paris Agreement, the study suggests. Economically disruptive confinement measures aren’t a replacement for long-term climate policies, according to Corinne Le Quéré, a professor of climate-change science at the University of East Anglia and an author of the paper.

“That effect will do nothing to tackle climate change in itself,” said Le Quéré, who chairs France’s High Council on Climate, “but it has showed us if you have coordinated action globally, if you have actions at the right scale, you can [make a] major dent in global emissions.”

In the paper, she and her coauthors advocated for large-scale deployment of renewable energy, improvements in remote communications for businesses and regional tourism and a swift return to public transportation as part of the COVID-19 pandemic recovery. The East Anglia professor also emphasized that investments in clean energy and industrial activity would stimulate the economy and improve public health through better air quality.

Le Quéré compared the annual amount of cuts needed to keep pace with the Paris Agreement — 1 billion to 2 billion metric tons each year — to reducing a Russia's or Japan's worth of emissions each year, referring to the fifth- and sixth-biggest emitters.

Yet carbon dioxide emissions are already rising as the pandemic gradually recedes and economies recalibrate. Global energy-related emissions in December were 2% higher than they were one year earlier as a result of “economic recovery and a lack of clean energy policies,” according to data released Tuesday by the International Energy Agency. Le Quéré said overall emissions in 2020 were probably not on track to fall without the pandemic.

And many countries’ Paris-tied plans to reduce their production of carbon dioxide have been judged as too weak, with one analysis finding annual reductions need to happen 80% faster than these plans currently dictate.

“My feeling is that most world leaders, they haven’t realized or internalized what it takes to tackle climate change,” Le Quéré said. “These good intentions, they now need to be translated into action plans, into targets within the next five years, into engagement of all your industries, of all your stakeholders, of the public.”

Some of the world’s largest countries have recommitted to decarbonizing in the past few months with stronger long-term goals. China and the U.S. have committed to net-zero emissions by 2060 and 2050, respectively, and the European Union upped its 2030 goal to 55% of 1990 levels, from 40%.

“I'm hopeful because I see we're making progress, and I'm concerned because I see this progress is just really not big enough and not fast enough,” Le Quéré said. “What is good about this study is that we show that there is progress, so there’s a point to what we’re doing and if you do things, the emissions go down, so I guess we can build on this.”

The study “Fossil CO₂ emissions in the post-COVID-19 era,” published March 3 in Nature Climate Change, was authored by Corinne Le Quéré and Matthew Jones, University of East Anglia; Glen Peters and Matthew Jones, Centre for International Climate and Environmental Research; Pierre Friedlingstein, University of Exeter and Sorbonne University; Josep Canadell, CSIRO Oceans and Atmosphere; Steven Davis, University of California, Irvine; and Robert Jackson, Stanford University.