The Paris Climate Agreement set the international goals to reduce carbon emissions so that we would not exceed 1.5 C warming. The Paris Climate Agreement is based on the research findings and recommendations of the Intergovernmental Panel on Climate Change (IPCC.)
The Paris Climate Agreement adopted the IPCC recommendation to limit carbon emissions to 1.6 tons per capita. globally by 2050. Currently, the world average is near 4 tons per capita.
To achieve that goal, the upper income economies need to reduce their carbon emissions to 3 tons per capita. The U.S. current per capita carbon emissions is 16.4 tons.
Thus, within the U.S., to keep under 1.5 C warming, we will have to reduce our per capita average from 16.4 tons to 3 tons per capita by 2050.