[aperson]

ps you may have trouble finding a source that "carbon" levels were at 1900ppm because we don't measure "carbon" in ppm. We measure different greenhouse gases that contain carbon, Like CO2 (carbon dioxide) and CH4 (methane) in PPM, some other greenhouse gases, like H2O (water vapor) don't even contain carbon. Maybe you mean that Jurassic CO2 concentration was 1900ppm? Would love to see some sources on that one too!