Has global warming (or AGW, or global climate change, or whatever name is popular this week) occurred in the past? Yes, without a doubt. Has global cooling occurred in the past? Yes, again, without a doubt. Are humans responsible for what has happened in the past? Since no fossils of cars or power plants have ever been found, the conclusion must be "No." Are humans responsible for the current global warming? Well, it all depends on who you ask. This source says "yes." This source says "no."
The primary point here is that there are two separate questions to consider. (1): Has global warming/cooling occurred, and does it continue to occur? Of that, there is no argument. As Al Gore is wont to say, "A consensus has been reached." (2): (and this is the heart of the global warming argument) Are humans causing what is currently occurring? Global warming advocates try, in my opinion formed from observations, to combine the two questions in an attempt to further their argument/cause. Global warming skeptics and nay-sayers do not examine the first question. Why should they? They examine what is currently happening (current being defined as in the last, say, 100 years - there were very few cars or coal-fired power plants 100 years ago) and are more and more reaching the conclusion that humans, regardless of what we do, cannot possibly overcome nature.
The politics of global warming is what most global warming advocates forward. The politics is entirely about control. For example, this source clearly explains the ultimate objective of global warming advocates: "... to justify demands for a more powerful government and that the government needs to assert more controls over energy production and consumption in order to stop the Earth from warming." Further, the Copenhagen Accord of 2009 calls for:
"... developed nations to provide $30 billion to help developing nations deal with the effects of climate change from 2010 to 2012. By 2020, the text [the Copenhagen Accord] says rich nations 'set a goal of mobilizing jointly $100 billion a year' for poor nations. The text says the money will go to the 'most vulnerable' developing nations."
Two questions. First, how is the US, although developed, considered rich? The US debt, the last time I looked, was over $16 trillion. Second, who do you think will pay the bulk of the $100 billion per year? I'll give you three guesses, and the first two don't count.
And this from Dr. William Tumminelli, lead author of a UN Intergovernmental Panel on Climate Change (IPCC) report: "We need to have strict international rules in place." Do rules equate to control?