They have allowed businesses to meet goals at costs below predictions and to receive a fair price for their products. These programs have placed government bodies in oversight roles where they can focus on enforcement and compliance, and avoid the awkward position of telling an industry how to run its operations. The acid rain issue polarized environmentalists, industry leaders and government regulators for more than a decade, but cap and trade broke this logjam and provided common ground upon which all parties could jointly craft a solution. Common Good Problems such as air pollution don't stop at state or national borders. Increasingly, our environmental challenges are global in nature, shared by everyone on the planet.
Greenhouse gases warm the atmosphere, no matter where they are produced on the globe.
Removing a ton of these gases helps to slow climate change, whether that ton is removed in the East or West, Northern or Southern hemisphere. Cap and trade programs can take into account the big picture - the common good.