The issue with any significant steps to curbing the climate or environmental impacts with laws or treaties is always: But the economy. It creates an incentive where someone doesn't follow the laws, burn everything they can to accelerate their economy, and take industry from other countries.
My proposal is thus: create a supranational treaty organization with a EPA like authority(or whatever the European equivalent is) that can inspect and fine companies in member organizations. Then any treaty members agree with the following conditions: The EPA can enter their nation freely, inspect, and are able to fine companies that break rules. Members send delegates to a session to create new rules democratically. And most importantly all members act as a cartel, imposing large tariffs on any country outside of the organization. So if US was in and Mexico was out, you couldn't just pollute in Mexico, without some massive tariff. This creates an economic incentive to be in and clean.
My proposal is thus: create a supranational treaty organization with a EPA like authority(or whatever the European equivalent is) that can inspect and fine companies in member organizations. Then any treaty members agree with the following conditions: The EPA can enter their nation freely, inspect, and are able to fine companies that break rules. Members send delegates to a session to create new rules democratically. And most importantly all members act as a cartel, imposing large tariffs on any country outside of the organization. So if US was in and Mexico was out, you couldn't just pollute in Mexico, without some massive tariff. This creates an economic incentive to be in and clean.