The last time that levels of atmospheric carbon dioxide were as high as they are today, Greenland was free of ice and the savanna and grassland ecosystems where humans evolved didn’t exist yet.
That’s the conclusion of a study published in Science Friday, which researchers say compiles “the most reliable data available to date” on atmospheric carbon dioxide levels over the last 66 million years.
“It really brings it home to us that what we are doing is very, very unusual in Earth’s history,” lead author Baerbel Hoenisch of the Columbia Climate School’s Lamont-Doherty Earth Observatory told Agence France-Presse.
By burning fossil fuels and clearing natural carbon sinks like forests, industrial capitalism has raised global carbon dioxide levels to 419 parts per million (ppm) today from around 280 ppm at the beginning of the industrial revolution.
“Rising atmospheric CO2 is the most obvious and startling expressions of our impact […]