The report of the working group-I to the sixth assessment report (AR6) of the Intergovernmental Panel on Climate Change (IPCC 2021) has clearly laid out the challenge before the world, which is already experiencing warming of about 1.07 degrees Celsius (C) (a likely range of 0.8C1.3C) as compared to the pre-industrial period (18501900). Carbon dioxide (CO2) emissions are the largest contributor to this warming. According to the IPCC (2021), about 2,390 (240) gigatonnes of CO2 (GtCO2) have been emitted cumulatively by the world between 1850 and 2019. While there is no doubt that the world needs multiple strategies to address climate change, it is very clear from the scientific evidence that reducing CO2 emissions will have the largest long-term impact on mitigating climate change, and therefore, this is where the world must urgently focus.
The AR6 has also once again underscored the relationship between cumulative emissions and the rise in global surface temperature, which has been long established in the scientific literature (IPCC 2013, 2021). This relationship between cumulative emissions and temperature rise is near linear and allows us to estimate a corresponding carbon budget for a particular probability of limiting temperature rise to either 1.5C or 2C or any other temperature limit.