IPCC Summary for Policymakers (SPM) https://www.ipcc.ch/...
Mitigation scenarios in which it is likely that the temperature change caused by anthropogenic GHG emissions can be kept to less than 2°C relative to pre‐industrial levels are characterized by atmospheric concentrations in 2100 of about 450 ppm CO2eq (high confidence)….
In the Advanced Global Atmospheric Gases Experiment (AGAGE), we continuously measure over 40 of these other GHGs in real time over the globe. If you convert these other GHGs into their equivalent amounts of CO2 that will have the same effect on climate, and add them to the NOAA measurements of CO2, you find that we are actually at 478 ppm of CO2 equivalents right now. In fact, we passed the 400 ppm back in about 1985. So, 478 not 400 is the real number to watch. That’s the number people should be talking about when it comes to climate change.