Apr 7, 2022 - Energy & Environment

Earth's CO2 levels to hit alarming milestone

Average monthly atmospheric CO2 levels at Mauna Loa Observatory
Data: NOAA and the Scripps Institution of Oceanography; Chart: Thomas Oide/Axios

Monthly average carbon dioxide (CO2) levels are very likely to hit or even exceed 420 parts per million during the month of April, according to readings at the Mauna Loa Observatory in Hawaii.

Why it matters: This is a new record high for human history, and very likely the highest level seen in 4.1 million to 4.5 million years.

  • Scientists tell Axios that the sustained year-to-year growth rates in CO2 concentrations are unprecedented.

Driving the news: The amount of CO2 in the air continues to increase as people burn fossil fuels and chop down rainforests for agriculture, among other activities.

Context: The data plotting the increase in CO2 is known as the Keeling Curve, named after Charles Keeling, who started and maintained the observations.

  • Charles Keeling's son Ralph continues his father's legacy by extending the data.
  • Ralph Keeling told Axios the first few days of April have shown CO2 levels at or above 420 ppm, and based on month-to-month growth rates, this will be the first month to eclipse this milestone.
  • "I think it's virtually a done deal," he said of the monthly average, noting it will increase further in May.

What they're saying: "CO2 is still rocketing up. If you look at the record, it's just relentless. So as much as people have been working hard and need to be working hard to slow the growth rate, we have to be honest that we haven't done much yet to actually curb the build-up," Keeling said.

  • Pieter Tans, who tracks greenhouse gases for the National Oceanic and Atmospheric Administration, said the speed of the CO2 increase is striking. Tans said CO2 will be "over 420 ppm" during April.
  • Coming out of the last ice age, he said, CO2 went up by about 80 ppm during 6,000 years. Yet now it's increasing by more than 2 ppm "every single year."
  • The 400 ppm milestone was eclipsed less than a decade ago, in 2013, and 440 ppm isn't far off, he warned. He described the growth rate as "an explosion" from a geological perspective.

The intrigue: The CO2 concentration numbers may seem abstract, but they correspond to huge upticks in the amount of heat being added to the oceans and atmosphere. This is melting ice caps and raising sea levels, as well as leading to increasingly destructive extreme weather events.

What's next: The typical annual peak in CO2 amounts at Mauna Loa occurs in May, before vegetation in the Northern Hemisphere soaks up the gas throughout the warm season.

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