At its likely peak for 2022, atmospheric CO2 hit levels in May not seen since the Pliocene era, 4.1 to 4.5 million years ago, NOAA reported Friday. At 421 parts per million, measured at the Mauna Loa Atmospheric Baseline Observatory in Hawaii, carbon pollution is now more than 50% higher than preindustrial levels, after record-breaking levels in 2020 and 2021. The last time atmospheric CO2 levels were this high on the only known habitable planet, Earth was essentially a flooded greenhouse with forests in the Arctic and sea levels 78 feet higher, submerging South Florida and coastal areas around the world. Humans, never mind human civilization, have never known such conditions. Four million years ago our Australopithecus ancestors were still working out how to walk on two legs.

“Watching these incremental but persistent increases in CO2 year-to-year is much like watching a train barrel down the track towards you in slow motion. It’s terrifying,” UW-Madison climate scientist Andrea Dutton told the AP. “If we stay on the track with a plan to jump out of the way at the last minute, we may die of heat stroke out on the tracks before it even gets to us.”  (AP, New York Times $, Gizmodo, Axios, Al Jazeera)