The Earth just reached a CO2 level not seen in 3 million years

Mauna Loa Observatory. CREDIT: AP Photo/Richard Vogel

Some records aren’t meant to be broken — but when it comes to climate change, humans still haven’t gotten the memo.

Last fall, the Earth passed a major climate milestone when measurements taken at Hawaii’s Mauna Loa Observatory showed that atmospheric concentrations of carbon dioxide had passed — potentially permanently — 400 parts per million.

This week, measurements taken from the same observatory show that yet another marker has been passed: Carbon dioxide in the Earth’s atmosphere, for the first time in modern record-keeping, has surpassed 410 parts per million.

Since measurements began in the 1950s at Mauna Loa, atmospheric concentrations of carbon dioxide have increased 42 percent increase from pre-industrial levels. Children born today will likely never live in a world with levels below 400 parts per million.

The last time Earth had comparable levels of atmospheric carbon dioxide was about three million years ago, during the mid-Pliocene. Back then, global average temperature was about 3.6–5.2°F (2–3°C) warmer than it is today. Sea levels were also higher, by about 15–25 meters. And while passing 400 parts per million permanently — or hitting a high of 410 parts per million, as happened on Tuesday — won’t trigger any immediate climate consequences, it is a stark reminder of the profound influence human activity is having on the planet.

Global concentrations of carbon dioxide increased rapidly in the past couple of years, thanks in part to a strong El Niño. El Niño patterns often shift the location of tropical rains, leaving tropical forests more susceptible to fires — fires that, in turn, release a lot of stored carbon into the atmosphere. But human activities — like the burning of fossil fuels for transportation or electricity, or the conversion of forests and grasslands into developed areas or farmland — have also contributed to the rise in atmospheric carbon dioxide, which has jumped from 280 parts per million in preindustrial times to now well over 400 parts per million.

The Keeling Curve. CREDIT: Scripps Institute of Oceanography

The measurements taken at Mauna Loa — continuously since 1958 — helped scientists create the Keeling Curve, named after Charles Keeling, the scientist who invented the precise method for measuring atmospheric carbon dioxide still used today. The curve has been called “an icon of modern science” for the way that it shows the striking increase in carbon dioxide over a half century of measurements.

The program at Mauna Loa is run jointly by the National Oceanic and Atmospheric Association (NOAA) and the Scripps Institute of Oceanography, which means that the program is vulnerable, at least in part, to the whims of federal funding. And while the Scripps Institute of Oceanography is a private institution, it has also received funds from the Department of Energy. It’s unclear whether funding for the program will continue under the Trump administration — Trump’s proposed skinny budget cuts much of NOAA’s research funding and cuts almost all domestic climate research funding.

Trump’s director of Office of Management and Budget, Mick Mulvaney, has said that the administration considers climate spending “to be a waste of your money.” The Department of Energy, under the Trump administration, has also suggested that it could refocus its mission on nuclear and fossil fuels.

Meanwhile, the carbon dioxide currently in the atmosphere will persist for decades — and levels are expected to keep rising, perhaps by another 2.5 parts per million by the end of this year.