Atmospheric Carbon Dioxide Reaches New High Despite Pandemic Emissions Reduction

Global carbon emissions in 2020 were lower than they were in 2019, but those reductions would need to be sustained for years to slow the climate crisis

Mauna Loa Atmospheric Baseline Observatory in Hawaii
A photo of the Mauna Loa Atmospheric Baseline Observatory in Hawaii where scientists measure atmospheric concentrations of the greenhouse gas carbon dioxide. Susan Cobb / NOAA Global Monitoring Laboratory

Concentrations of carbon dioxide in Earth’s atmosphere have crested 419 parts per million, marking the thickest blanket of the heat-trapping gas that has enveloped our planet in more than four million years, researchers from the Scripps Institution of Oceanography and the National Oceanic and Atmospheric Administration (NOAA) announced this week.

This new peak of the primary greenhouse gas driving climate change makes blindingly clear that the temporary reductions in emissions associated with the coronavirus lockdowns last year were just that, temporary.

In April 2020, during the most restrictive phase of the lockdowns aimed at curbing the virus’ spread, the world emitted 17 percent less carbon on a daily basis than it did in the same quarter of 2019. Yet, May 2020 saw carbon dioxide (CO2) concentrations climb to a monthly average of 417 parts per million, which was—until now—the highest level ever observed.

The Keeling Curve Hits 420 PPM

Reporting for the New York Times, Brad Plumer writes that the world’s carbon emissions in 2020 were 5.8 percent lower than they were in 2019, which is the largest annual decline ever measured. But even this dramatic decline did little to offset climate change writ large.

That’s because CO2 hangs around for a really long time once it’s emitted—between 300 and 1,000 years, according to NASA. This long residence time causes climate researchers to compare Earth’s atmosphere to a bucket that human activities have been rapidly filling up with carbon dioxide since the Industrial Revolution.

"The ultimate control knob on atmospheric CO2 is fossil-fuel emissions,” says Ralph Keeling, a Scripps geochemist who measures carbon dioxide concentrations at Hawaii’s Mauna Loa Observatory, in a statement, “but we still have a long way to go to halt the rise, as each year more CO2 piles up in the atmosphere. We ultimately need cuts that are much larger and sustained longer than the COVID-related shutdowns of 2020."

Jason Bordoff, founding director of Columbia University’s global energy center, tells Brady Dennis and Steven Mufson of the Washington Post that while 2020 may have seen historic emissions reductions, they required more than half the world’s population to be under lockdown which isn’t exactly feasible. The fact that “emissions ONLY fell 6 percent should be a sobering reminder of how staggeringly hard it will be to get to net zero and how much more work we have to do,” Bordoff wrote to the Post via email.

Human activities release around 40 billion metric tons of CO2 into the atmosphere annually. To avoid the worst impacts of climate change and stall the annual hike in atmospheric CO2, Corinne Le Quéré, a climate scientist at the University of East Anglia, tells the Post that global emissions will quickly need to approach zero.

A 2019 report from the United Nations Environment Program says global greenhouse gas emissions would need to fall by 7.6 percent a year from 2020 until 2030 to keep warming below the 1.5-degree-Celsius (2.7 degrees Fahrenheit) threshold identified by the Paris Agreement.

Princeton University climate scientist Michael Oppenheimer tells Seth Borenstein of the Associated Press (AP) that “the world is approaching the point where exceeding the Paris targets and entering a climate danger zone becomes almost inevitable.”

The new highest-ever-measured concentration of atmospheric CO2 is also 50 percent higher than pre-industrial levels, which were 280 parts per million. Speaking with the AP, Pieter Tans, a senior scientist with NOAA’s Global Monitoring Laboratory, compared this meteoric rise with the increasing atmospheric CO2 associated with Earth’s emergence from the last ice age, which was an increase of just 82 parts per million spread across 6,000 years.

Around four million years ago, the last time CO2 was as prevalent in the atmosphere as it is now, Earth’s oceans were 78 feet higher, the climate was an average of 7 degrees Fahrenheit warmer and the Arctic tundra may have been home to vast forests, according to NOAA.

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