Last Time CO2 Levels Hit 400 Parts Per Million & Humans Were Alive -- Never | CleanTechnica

Last Time CO2 Levels Hit 400 Parts Per Million & Humans Were Alive -- Never | CleanTechnica

“It shows a huge warming – unprecedented in human history,” said Prof Scott Elias, at Royal Holloway University of London, and not involved in the work. “It is a frightening experiment we are conducting with our climate.”