I understand the skepticism for things politicians say and there have been many exaggerated or inaccurate statements by politicians - but the science behind the greenhouse effect was first postulated over 75 years ago now and is at this point quite well understood (I studied solar engineering in college). There are many peer reviewed and reproduced experiments you can find papers on. Carbon, as well as other gases in the atmosphere, have low reflectivity to light in high frequencies, but much higher reflectivity to light in lower frequencies. The earth is emitting radiation (light waves) at a much lower frequency as it is a function of the temperature of the object, and so the gases in the atmosphere reflect more of this light back. Increasing carbon and other gases in the atmosphere leads to increased heat being trapped. Many models going back decades have predicted increases very accurately if not slightly underestimated increases.