It is very expensive to reduce emissions, and unless you’re willing to build nuclear power plants, there is no substitute for coal, natural gas, and oil,” said Ebell. “In the transportation sector, there is no real alternative to gasoline and diesel from petroleum  think a lot of these countries see these agreements as a way to show how virtuous they are and to feel good about themselves, but the actual work of reducing greenhouse gas emissions is very difficult,” Ebell said. “It’s very easy for governments to talk big, but very difficult to follow through and actually cut greenhouse gas emissions to meet commitments.