The only role of government as it relates to the environment is to protect individual rights, primarily through the legal system. For example, if my pasture is downstream from an oil-drilling site, and runoff poisons my cattle feed, my rights have been violated and I may sue the drilling company for compensation. If my fish farm is damaged by an oil spill, and my expected harvest objectively reduced, I can take the polluter to court. And, if I can objectively prove that my individual rights are violated by increased total CO2 emissions, the same principle applies.
Think Right or Wrong, Not Left or Right 