Proponents of the Global Warming theory...

This is from the online encyclopedia Wikipedia:

"Reasons given by supporters of the global warming theory:
Supporters of the global warming theory assert that gas bubbles trapped in ice cores give us a detailed record of atmospheric chemistry and temperature back more than four hundred thousand years, with the temperature record confirmed by other geologic evidence. This record tells us that carbon dioxide and temperature rise and fall tightly together.

The recent rise in carbon dioxide and other greenhouse gases is greater than any in hundreds of thousands of years and this is human-caused, shown by isotopic signature of CO2 from fossil fuels. We know carbon dioxide captures IR radiation and converts it to heat because we use these physics to measure carbon dioxide concentration the historical temperature record shows a rise of 0.4–0.8 °C over the last 100 years. The urban heat island effect makes no significant contribution.

The current warmth is unusual in the past 1000 years (see Temperature record of the past 1000 years).

The warming of the last 50 years is likely caused by human activity (see attribution of recent climate change), using analysis based on climate modeling; and that natural variability or solar variation cannot explain the recent change.

Carbon dioxide is a first order forcing on climate change—other effects such as water vapour greenhouse effects are either roughly constant over time, act as amplifiers, or do not have a large effect. Humankind is performing a great geophysical experiment and if it turns out badly—however that is defined—we cannot undo it. We cannot even abruptly turn it off. Too many of the things we are doing now have long-term ramifications for centuries into the future. Climate models can reproduce this trend, but only when using greenhouse gas.

Climate models predict more warming, and other climate effects (sea level rise, more frequent and severe storms, drought and heat waves, etc) in the future. For instance, Atlantic hurricane trends have been recently linked to climate change, June 2006. Action should be taken now to prevent or mitigate warming (see Precautionary principle).

The IPCC reports correctly summarise the state of climate science. There is a scientific consensus behind all of the above.
Our existence is poised within a fluid-dynamic, ocean-atmosphere-biosphere system, where non-linear feedbacks are common and where climate states are only relatively stable (i.e., "metastable"). Unknown unknowns are likely to surprise us, particularly if they trigger a non-linear, positive feedback that flips climate to a new meta-stable state.

Proponents of global warming tend to support the IPCC position and thus represent a broadly unified viewpoint, though with considerable differences over what action should be taken. Optionally, supporters may go on to point out that there is a good chance that the future changes may be undesirable, and that planning to avoid or mitigate them would be a good idea. Only 2 of the 120 contributing authors to the IPCC TAR are known to have voiced any complaint.

Science Magazine analyzed 928 peer-reviewed scientific papers on global warming published between 1993 and 2003 (Oreskes, 2004). Not a single one challenged the scientific consensus the earth’s temperature is rising due to human
activity."

The IPCC referred to is the Intergovernmental Panel on Climate Change and was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to assess the "risk of human-induced climate change". The Panel is open to all members of the WMO and UNEP.

IPCC reports are widely cited in almost any debate related to climate change. The reports have been influential in forming national and international responses to climate change. A small but vocal minority (less than 1.5%) of the scientists involved with the report have accused the IPCC of bias.