But surely Carter is merely part of what most people regard as a tiny cadre of "climate change skeptics" who disagree with the "vast majority of scientists" Gore cites?
No; Carter is one of hundreds of highly qualified non-governmental, non-industry, non-lobby group climate experts who contest the hypothesis that human emissions of carbon dioxide (CO2) are causing significant global climate change. "Climate experts" is the operative term here. Why? Because what Gore's "majority of scientists" think is immaterial when only a very small fraction of them actually work in the climate field.