Mr H your post is appreciated and well considered, but l think you will agree that scientific "proof" is sometime not possible, at least with the tools we currently possess. But scientific "opinion" is not based on air! Scientific opinion is based on evidence gathered and verified. There is "scientific proof" that the globe is warming and there is "scientific opinion" based on evidence that this warming is at least partly based on human activity which can be changed. I agree that any effort to slow the trend to the extent we can by changing human behavior has to be an international effort to be successful. I do not agree that we as a nation should now simply throw up our hands and say "the world will never take up this effort so why try" before we even try. I also do not agree that the economic well being of the US trumps all (pun intended)!
As an afterthought: I look at the situation with climate change in somewhat the same way l do, correctly or otherwise, the "theory" of evolution. Evolution is a "fact", what drives evolution is the "theory". If you get either part of evolution wrong there is little or no consequence for current life on earth...if we get either part of climate change wrong there is at least the potential for disaster.