Paleoclimatological Context and Reference Level of the 2 °C and 1.5 °C Paris Agreement Long - Term Temperature Limits The Paris Agreement adopted in December 2015 during the COP21 conference stipulates that the increase in the global average temperature is to be kept well below 2 °C above «pre-industrial levels» and that efforts are pursued to limit the temperature increase to 1.5 °C above «pre-industrial levels.»