Here's what I don't understand - the US emits in the range of 15-20% of the world's total carbon emissions. If we were to reduce that by 20% (which would be a h

Here's what I don't understand - the US emits in the range of 15-20% of the world's total carbon emissions. If we were to reduce that by 20% (which would be a huge undertaking), we're talking about a 4% worldwide decrease at most. In order for any drastic change to happen, the US cannot do it alone. Therefore, domestic policy is not the place where a real impact can be made. It's a foreign policy matter, and something that can really only be accomplished through treaties and the like. China's contribution to carbon emissions is approximately twice the US's. Trump wants to threaten to harm China's economy through tariffs. Why not combine those two goals and craft legislation so that tariffs are set on a sliding scale based on the origin nation's total carbon emissions?