If you're reading this, you're one of the very first humans to ever live on an Earth with 415 parts-per-million atmospheric carbon dioxide — last seen 3mil years ago.

Yes, that means warming—but higher CO2 levels also hamper your ability to think: https://t.co/Hu8rJAEuIm

— Eric McDaniel (@ericmcdanieldc) May 13, 2019