This actually might be a good thing. These groups would have to prove global warming is caused by greenhouse gasses.
I don't think you can "prove it". It's a 'reasonable' theory, but even if a civil case, I don't think you could prove it by a "Preponderance of the Evidence." Not enough data in last 50-100 years to overcome millions of years of 'natural' climate changes.
http://www.opic.gov/GeneralOPIC/faqs.htm - OPIC FAQ's
Q - If OPIC operates at no cost to the taxpayer, how can you sue it for overseas projects they financially back? It looks like an 'insurance company'
"Charging user-fees for its services, OPIC operates at no net cost to the American taxpayer. OPIC’s political risk insurance, project finance and investment funds fill a commercial void, create a level playing field for U.S. businesses and support development in emerging economies."