The US is back to 1964 levels of CO2 output. How? Regulation? No. Some other top-down control? No.
The free market. Oil prices are up so the invisible hand drives people to drive automobiles that are more efficient. Natural gas is becoming more abundant and less expensive thanks to many technology advances and well finds in the US, so power companies switch from coal to natural gas. The market is “magically” reducing pollution. No central plan. No design to achieve this outcome. No regulation. No carbon tax. But it happens – the world becomes a better place. In the entire history of humanity this is true – the world becomes a better place.