Even controlling for the harm to the environment, you have to consider the harm to our foreign policy if we become unable to uphold any agreement for more than 4 years.
I'd hope our counterparts from other nations would be sophisticated enough about our Constitutional system to understand that what one President can agree to without enshrining it in law through Congress, a later President can just as easily disregard.
I agree. And it's true that the Paris agreement should have gone through the treaty ratification process. But I'm not convinced our president understands that difference and I definitely do not believe that his behavior is motivated by a comprehension of those differences rather than the content of the agreement.
