All the world's people will benefit from cheaper clean energy and lower carbon emissions. China and the U.S. will both benefit from the expansion of the global market for clean energy. They will both benefit from joint research initiatives, intellectual property and technology sharing, and the reduction of distorting trade barriers. America happens to be particularly strong in research and tech development; China happens to be particularly strong in economies of scale. Those are complementary strengths that, in a sane world, would produce mutual benefit.