Michael Mann: We're Already On Our Way to "Blowing Past" 1.5 Degrees Global Warming
Atmospheric CO2 is currently well above 400 ppm (horizontal dotted line; right scale). This chart, going back to the Cambrian Period, shows how unusual the current situation is. The last time CO2 was greater than 400 ppm was when the Indian subcontinent slammed into Asia from the south (note the rise and fall in CO2 around 50 million years ago).