Other Answers (12)

• The global temperature data of the past 100+ years is good evidence of global warming:
  http://www.columbia.edu/~jeh1/mailings/2...
  
  Here%26#039;s a detailed paper that describes the greenhouse effect, with direct evidence including the temperature of Venus:
  http://www.ias.ac.in/resonance/Mar1996/p...
  %26quot;It is interesting to note that in the absence of a greenhouse effect, the earth’s mean temperature would have been 255°K, instead of the observed value of 288°K. Greenhouse warming is thus about 33°K. This is much more pronounced around the planet Venus, whose atmosphere contains over 90% carbon dioxide (CO2), a prominent greenhouse gas. Without a greenhouse effect the mean surface temperature of Venus would have been 227°K, but greenhouse warming raises it to 750°K. This represents warming by 523°K!%26quot;
  
  Polar ice melting at rates 42 times the average of the past 4700 years is evidence:
  http://www.spiegel.de/international/worl...
  %26quot;The paper also states that the thickness of the Pine Island Glacier has shrunk by an average of 3.8 centimeters annually over the past 4,700 years. But the Smith and Pope glaciers have only lost 2.3 centimeters of their thickness annually during the past 14,500 years. Satellite measurements taken between 1992 and 1996, though, show a loss of 1.6 meters in thickness per year on the Pine Island Glacier -- a figure that represents 42 times the average melt of the past 4,700 years.%26quot;
  
  Here%26#039;s the scientific background of carbon science:
  http://www.aip.org/history/climate/co2.h...
  
  We know it%26#039;s warming, and we%26#039;ve measured how much:
  
  http://www.epa.gov/climatechange/science...
  
  Scientists have a good idea how the Sun and the Earth%26#039;s natural cycles and volcanoes and all those natural effects change the global climate, so they%26#039;ve gone back and checked to see if they could be responsible for the current global warming. What they found is:
  
  Over the past 30 years, all solar effects on the global climate have been in the direction of (slight) cooling, not warming. This is during a very rapid period of global warming.
  
  http://news.bbc.co.uk/2/hi/uk_news/62902...
  http://www.pubs.royalsoc.ac.uk/media/pro...
  
  So the Sun certainly isn%26#039;t a large factor in the current warming. They%26#039;ve also looked at natural cycles, and found that we should be in the middle of a cooling period right now.
  
  %26quot;An often-cited 1980 study by Imbrie and Imbrie determined that %26#039;Ignoring anthropogenic and other possible sources of variation acting at frequencies higher than one cycle per 19,000 years, this model predicts that the long-term cooling trend which began some 6,000 years ago will continue for the next 23,000 years.%26#039;%26quot;
  
  http://en.wikipedia.org/wiki/Milankovitc...
  http://www.sciencemag.org/cgi/content/ab...
  
  So it%26#039;s definitely not the Earth%26#039;s natural cycles. They looked at volcanoes, and found that
  
  a) volcanoes cause more global cooling than warming, because the particles they emit block sunlight
  
  b) humans emit over 150 times more CO2 than volcanoes annually
  
  http://volcano.und.edu/vwdocs/Gases/man....
  
  So it%26#039;s certainly not due to volcanoes. Then they looked at human greenhouse gas emissions. We know how much atmospheric CO2 concentrations have increased over the past 50 years:
  
  http://en.wikipedia.org/wiki/Image:Mauna...
  
  And we know from isotope ratios that this increase is due entirely to human emissions from burning fossil fuels. We know how much of a greenhouse effect these gases like carbon dioxide have, and the increase we%26#039;ve seen is enough to have caused almost all of the warming we%26#039;ve seen over the past 30 years (about 80-90%). You can see a model of the various factors over the past century here:
  
  http://en.wikipedia.org/wiki/Image:Clima...
  
  This is enough evidence to convince almost all climate scientists that humans are the primary cause of the current global warming.
  
  Dang that saved a lot of typing!
  
  Climate change is fact. Global warming, as caused by man, is theory. The beef industry%26#039;s cows contibue the equivalent in greenhouse gases to the atmosphere as the entire worlds automobile sector (An Inconvenient Book). CO2 is the least of the green house gases. Methane is far worse when it comes to heat retention.
  
  I haven%26#039;t made up my mind what I believe yet, but I have enough sense to read into BOTH sides before forming an opinion.
  
  Al Gore famously documented the retreats of several glaciers in his film.
  
  Isotope ratios and gas concentrations of ancient atmosphere trapped inside glaciers allow us to see that carbon and temperature have been related for thousands, if not millions of years.
  
  The science used for global warming is routinely used to predict short-term weather (will it rain today).
  
  To determine that *this* year is on average, warmer than *last* year, takes *lots* of data, computers, and a data reporting system difficult for any single person to comprehend.
  
  %26quot;Earth Simulator%26quot;
  http://www.es.jamstec.go.jp/index.en.htm...
  
  http://en.wikipedia.org/wiki/Earth_Simul...
  http://scienceandpublicpolicy.org/images...
  http://icecap.us/images/uploads/HF_CLIMA...
  Data @ NASA GISS: GISS Surface Temperature Analysis: Graphs
  
  http://www.sciencemag.org/cgi/content/fu...
  BEYOND THE IVORY TOWER: The Scientific Consensus on Climate Change -- Oreskes 306 (5702): 1686 -- Science
  
  http://www.sciencemag.org/cgi/content/ab...
  Causes of Climate Change Over the Past 1000 Years -- Crowley 289 (5477): 270 -- Science