Per - capita emissions The total amount of greenhouse gas emitted by a country per unit of population. (bbc.com)
I've gone a step further and tried to assign likely nationwide greenhouse gas emissions totals for the major plans on the table right now: (slate.com)
Current global CO2 emissions total approximately 30 billion tons (Gt) per year, with the USA contributing approximately 20 % (5.8 Gt per year). (skepticalscience.com)