The 2015 Paris Agreement established the goal of keeping planetary warming to below 2°C while pursuing efforts to limit warming to 1.5°C.
That 0.5°C difference in warming is critical.
The world is quickly depleting its 1.5°C carbon budget.
According to the IPCC’s sixth assessment report, as of January 1, 2020, the remaining global carbon budget for a good probability (67% chance or better) of avoiding more than 1.5°C warming is 340-400 Gt CO2 (AR6 budget).
To meet this budget CO2 emissions must be reduced 50-65% by 2030 and to zero CO2 emissions by 2040. Waiting until 2050 to achieve zero emissions means giving up the 1.5°C goal altogether.