Anthropogenic Global Warming

Through the Earth's history, the environment has ever been in flux.  We're presently being told that the Earth is warming at an alarming rate.  We're told that this is due to an excess of carbon dioxide being dumped in the atmosphere.  Finally, we're being told that the only way we can save ourselves is by implementing costly schemes to control our carbon emissions.
Before we jump headlong into the Great Global Warming bandwagon, we have some basic questions to ask:

  1. Is the Earth really warming.  If so, is it really unprecedented and is it at an "alarming" rate?
  2. If the Earth is warming, is man-made CO2 really the culprit?
  3. If the Earth is really warming, is it truely dangerous?  What is the Earth's optimum temperature?