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417.1 ppm: Atmospheric CO2 Levels Reach Three-Million-Year High

Atmospheric carbon dioxide levels have reached a three-million-year high, at 417.1 parts per million (ppm), despite the 17% drop in daily emissions brought about by the coronavirus lockdown, according to annual measurements at the atmospheric research lab at Mauna Loa, Hawaii.

The new figures, published last Thursday by the U.S. National Atmospheric and Oceanic Administration (NOAA), capture the annual peak in CO2 levels at the end of May, and reflect a 2.4 ppm increase over 2019, The Associated Press reports. By contrast, the Washington Post says, the annual growth rate in the 1960s was about 0.8 ppm.

This year’s reading is once again the highest since atmospheric measurements began in 1958, the highest in human history, and likely the highest in three million years, the Post states. “The last time there was this much CO2 in the atmosphere, global average surface temperatures were significantly warmer than they are today, and sea levels were 50 to 80 feet (15 to 24 metres) higher,” the paper says.

The Post’s coverage digs into the various factors—beginning with human activity—that influence the rise in atmospheric concentrations.

“Even though emissions of carbon dioxide from the burning of fossil fuels dropped by as much 17% in April, it was a brief decline,” AP writes, citing NOAA senior scientist Pieter Tans. “Carbon dioxide can stay in the air for centuries, so the short-term reductions of new carbon pollution for a few months didn’t have much of a big-picture effect.”

“It illustrates how difficult it is—what a huge job it is—to bring emissions down,” Tans told the news agency. “We are really committing the Earth to an enormous amount of warming for a very large time.”

“The buildup of CO2 is a bit like trash in a landfill. As we keep emitting, it keeps piling up,” explained Ralph Keeling, director of the Scripps Institution of Oceanography CO2 monitoring program, whose late father, Charles David Keeling, began the measurements at Mauna Loa.

“Because atmospheric levels of CO2 are cumulative, they will continue to increase until net emissions are cut to zero,” the Post explains. “They will not decrease until human activities and natural ecosystems are removing more greenhouse gases than is going into the air.”

Which is why “the [coronavirus] crisis has slowed emissions, but not enough to show up perceptibly at Mauna Loa,” Keeling added. “What will matter much more is the trajectory we take coming out of this situation.”

“The rise in atmospheric carbon dioxide levels is relentless, and this means the costs of climate change to humans and the planet continue to rise relentlessly as well,” said University of Michigan environment dean Jonathan Overpeck.