Even in the 64 countries where carbon dioxide pollution is falling, it would have to fall 10 times faster to prevent potentially catastrophic, irreversible climate changes, according to a new scientific analysis of global CO₂ emissions since the signing of the Paris pact five years ago.

The Global Carbon Project, an international scientific collaboration, published these findings today in the journal Nature Climate Change. Among the 64 countries with declining emissions, the reduction in carbon dioxide amounted to 160 million metric tons a year from 2016 to 2019 compared to the average from 2011 to 2015. Over the same time period, another 150 countries saw CO₂ rise by an average of 370 million tons a year. The unprecedented emissions drop due to the pandemic makes 2020 difficult to compare against longer-term trends. GCP scientists found that fossil-fuel CO₂ emissions fell last year by 7% globally, to 34 billion tons, in line with the International Energy Agency’s estimate released yesterday of an almost 6% fall in CO₂. Last summer, the research firm Rhodium Group estimated that Covid-19-related emissions reductions cost in the range of $3,200 to $5,400 per metric ton, or 50 or 100 times higher than some economists say is warranted.

GCP’s analysis also follows a report last week from the United Nations showing that countries’ latest goals submitted under the Paris agreement would lower emissions only half-a-percent by 2030. By then, the world needs to halve its emissions, according to a landmark 2018 report from the UN’s Intergovernmental Panel on Climate Change, in order to keep global temperature rise below 1.5° Celsius, a crucial tipping point. The world has already warmed about 1.2°C since the mid-19th century.

Corinne Le Quéré, Royal Society Research Professor of climate science at the University of East Anglia and the GCP paper’s lead author, said that 2021 will be make-or-break. “This year is the most important year for tackling climate change because we’re coming out of this pandemic. Governments are making big investments,” she said, which will have a determinative influence on the course of climate change.

The challenge the world faces now is to replicate that drop in emissions every year from now through 2050—while promoting economic growth, not quarantine and contraction—or else face increasingly dire environmental consequences. Emission levels won’t stay this low, the authors write, because “temporary measures have little impact on the fossil-fuel based infrastructure that sustains the world economy.”

China—the world’s biggest polluter, which last year pledged to reach net-zero carbon emissions by 2060—belongs to the “upper-middle-income” group of economies, along with 98 others. Collectively, they emit 51% of global CO₂. This group saw their emissions rise 30% between 2005 and 2019, although that has tapered off considerably since 2016. Emissions data released last week by China’s National Bureau of Statistics showed a total rise in emissions of more than 1% for 2020. More than two-thirds of 36 “high-income” nations are seeing emissions fall.

With more than 2,000 climate change-related laws or policies in place in different countries, government action “appears to have played a key role in curbing the growth in emissions” in the five years before the pandemic, Le Quéré and her co-authors wrote. Nations with declining emissions are largely getting there by winding down their coal plants and adding renewable power to their grids. What they’re not doing is adding additional fossil-fuel generation. “That’s not helpful,” Le Quéré said.

Industry has seen some efficiency gains, which “happens all the time,” she said, “It’s the nature of this sector” to seek money- and resource-saving measures. Addressing transport- and buildings-related emissions are critical next steps for countries that want to achieve a steeper drop in their greenhouse pollution.