Global warming is real and mostly caused by us. The proof is overwhelming. This will be long, and much of the proof is in the links:
This is science and what counts is the data.
"I wasn’t convinced by a person or any interest group—it was the data that got me. I was utterly convinced of this connection between the burning of fossil fuels and climate change. And I was convinced that if we didn’t do something about this, we would be in deep trouble.”
Vice Admiral Richard H. Truly, USN (Ret.)
Former NASA Administrator, Shuttle Astronaut and the first Commander of the Naval Space Command
Here are two summaries of the mountain of peer reviewed data that convinced Admiral Truly and the vast majority of the scientific community, short and long.
http://www.globalwarmingart.com/wiki/Image:Climate_Change_Attribution.png
http://ipcc-wg1.ucar.edu/wg1/wg1-report.html
summarized at:
http://www.ipcc.ch/SPM2feb07.pdf
It's (mostly) not the sun:
http://solar-center.stanford.edu/sun-on-earth/FAQ2.html
And the first graph above shows that the sun is responsible for about 10% of it. When someone says it's the sun they're saying that thousands of climatologists are stupid and don't look at the solar data. That's ridiculous.
Science is quite good about exposing bad science or hoaxes:
http://www.cs.cmu.edu/~dst/ATG/polywater.html
There's a large number of people who agree that it is real and mostly caused by us, who are not liberals, environmentalists, stupid, or conceivably part of a "conspiracy". Just three examples of many:
"Global warming is real, now, and it must be addressed."
Lee Scott, CEO, Wal-Mart
"Our nation has both an obligation and self-interest in facing head-on the serious environmental, economic and national security threat posed by global warming."
Senator John McCain, Republican, Arizona
“DuPont believes that action is warranted, not further debate."
Charles O. Holliday, Jr., CEO, DuPont
There's a lot less controversy about this is the real world than there is on Yahoo answers:
http://www.worldpublicopinion.org/pipa/articles/home_page/412.php?lb=hmpg1&pnt=412&nid=&id=
And vastly less controversy in the scientific community than you might guess from the few skeptics talked about here:
http://en.wikipedia.org/wiki/Scientific_opinion_on_climate_change
http://www.sciencemag.org/cgi/content/full/306/5702/1686
"There's a better scientific consensus on this [climate change] than on any issue I know... Global warming is almost a no-brainer at this point. You really can't find intelligent, quantitative arguments to make it go away."
Dr. Jerry Mahlman, NOAA
Good websites for more info:
http://profend.com/global-warming/
http://environment.newscientist.com/channel/earth/dn11462
http://www.ucsusa.org/global_warming/science/
http://www.realclimate.org
"climate science from climate scientists"