"GLOBAL WARMING IS A SCIENTIFIC FACT... to argue against this is like the creationists saying evolution is a theory without proof..."

The affect of human activity on Global temperatures is unknown.
The affect of increases in CO2 content is unknown.
The most significant affect on Global temperature are fluctuations in output of the Sun. The CO2 in the atmosphere is a green house gas, but CO2 in our atmosphere is a trace gas, it's green house affect is dwarfed by the greenhouse affect of water vapor, and Methane another trace gas, lb per lb is a more potent greenhouse gas than CO2.
If you could half the human output of CO2, you could not predict how much this would affect global temperture. If you double the human output of CO2 you can not predict how this would affect global temperature. Global temperatures can not be predicted- no scientist can predict whether global temperature will rise or fall in the coming year as compared to present year. Nor could scientist predict in next decade what global temperature will be.

Validity Of Global Climate Change Study Tool Doubted:
http://unisci.com/stories/20011/0109014.htm

"The scientific facts regarding climate change in general should be pointed out. The global warming hypothesis claims that man-made emissions of carbon dioxide and other gases have caused global temperature to increase in the 20th century and will cause further increase in the 21st century, with abundant negative side effects. This hypothesis is not supported by scientific observations. The 20th century temperature increases largely occurred prior to the largest increase in atmospheric carbon dioxide. The widely acclaimed temperature increases in the 1980s and 1990s most likely are flawed readings affected by urban heat-island effects: independent atmospheric readings show relatively constant global temperatures for the past 50 years. Despite claims to the contrary, a majority of scientists (both in general and in fields related to atmospheric physics) do not accept the global warming hypothesis as fact. "
http://www.johnstonsarchive.net/environment/sealevel.html