It's only three minutes, but that's all it takes to explain the basics.
Following that is an hour long lecture where this University of San Diego, Professor of History and Science Studies, Naomi Oreskes PhD. describes her research which documents the background of the orchestrated attack on climate science.
Published onNaomi Oreskes explains with great clarity the driving force behind climate denial - aversion to the political and economic implications of climate change.
UPDATE: Some commenters are asking about evidence that humans are causing global warming. A summary is provided at http://sks.to/evidence and http://sks.to/agw with links to the many peer-reviewed papers that provide empirical evidence for human caused global warming.