Al Gore has simply recently seized some popular attention with a movie, which is wonderful, but he didn’t create the idea of global warming any more than he created the Internet. Warnings about CO2 increases in the atmosphere are about 50 years old (see article below), and climate change has been a serious concern of scientists which has been compellingly explained in schools and media for decades.
If you are actually interested in facts (as opposed to the latest politics or popular consciousness of science), read up about science and scientists. An easy way to start is to move from movie theatres and US entertainment/“news” media to at least, say, European “news” media. See for example this article on Charles David Keeling’s observations since 1957 on the BBC News web site: http://news.bbc.co.uk/2/hi/science/nature/7120770.stm