The concentration of carbon dioxide in the atmosphere hit 415.39 parts per million (ppm) over the weekend — the highest level seen in some 3 million years, before humans existed, according to scientists at the Mauna Loa Observatory in Hawaii. CO2 levels are now rising 3 ppm each year, up from an average 2.5 ppm over the last decade, the scientists said.
“Every year it goes up like this we should be saying ‘No, this shouldn’t be happening. It’s not normal,’” Ralph Keeling, director of the Scripps CO2 Program, said in a statement. “This increase is just not sustainable in terms of energy use and in terms of what we are doing to the planet.”
The last time CO2 levels were this high was during the Pliocene Epoch, 5.3 to 2.6 million years ago, when the Earth was several degrees warmer, sea levels were an estimated 50 feet higher than they are today, and forests grew as far north as the Arctic. “Earth was a very different place,” Rob Jackson, a professor of earth system science at Stanford University, told NBC News. “You would hardly recognize the land surface, and my gosh, we don’t want to go there.”
Based on current emissions, scientists estimate CO2 levels could hit 500 ppm in as little as 30 years. “At the present pace, we could reach that well within a lot of people’s lifetimes,” Keeling told NBC News.
Ralph Keeling’s father, Charles David Keeling, was instrumental in developing the technology to accurately measure CO2 concentrations in the atmosphere, and he began doing so in 1958 at the Mauna Loa Observatory. That 61-year record has proven to be the gold standard globally for measuring the rise in anthropogenic carbon dioxide. The “Keeling Curve” is a graph that vividly depicts how atmospheric concentrations of CO2 have shot upward since the mid-20th century.
For more on how the world passed the 400 ppm threshold, and why it matters, click here.