Scientific American: February is one of the first months since before months had names to boast carbon dioxide concentrations at 400 parts per million.* Such CO2 concentrations in the atmosphere have likely not been seen since at least the end of the Oligocene 23 million years ago, an 11-million-year-long epoch of gradual climate cooling that most likely saw CO2 concentrations drop from more than 1,000 ppm. Those of us alive today breathe air never tasted by any of our ancestors in the entire Homo genus.
Homo sapiens...