Glad to hear you want to check out the DVD films I listed. Howard and Michelle Hall are world famous underwater photographers, most highly noted for IMAX film production and conservation minded ocean films.
Though Global Warming has been proven not to be a hoax but a very real scientific phenomenua. While the causes of Global Warming (i.e. natural warming of Earth's atmosphere or human related causes such as burning of fossil fuels) have been a subject of debate, I dont know of any science minded conservationist that doesnt view Global Warming as a very real problem.
Michael Crichton (author of Jurassic Park) wrote a novel called, State of Fear, where he said that the scientific community had manufactored Global Warming to incite panic in the public. This though is a work of fiction that carries no more real truth then his other novel Jurassic Park. Here is a link to a very detailed article on Global Warming and cites some potential, human and natural causes. http://en.wikipedia.org/wiki/Global_warming