 In other words, if net anthropogenic CO2 emissions are kept above zero, a global warming of 1.5°C and more will eventually be reached.The value of the "total" net anthropogenic CO2 budget since the pre-industrial era is not assessed in the report.Estimates of 400–800 GtCO2 (gigatonnes of CO2) for the "remaining" budget are given (580 GtCO2 and 420 GtCO2 for a 50% and 66% probability of limiting warming to 1.5°C, using global mean surface air temperature (GSAT);
or 770 and 570 GtCO2, for 50% and 66% probabilities, using global mean surface temperature (GMST)).