The higher the number, the greater the government’s justification for compelling polluters to reduce the emissions that are dangerously heating the planet. During the Obama administration, White House economists calculated the social cost of carbon at $42 a ton. The Trump administration lowered it to less than $5 a ton. Under President Biden, the cost was returned to Obama levels, adjusted for inflation and set at $51.

The new estimate of the social cost of carbon, making its debut in a legally binding federal regulation, is almost four times that amount: $190 a ton.