Discussion:
According to the IPCC AR4 Synthesis Report:
"Global GHG emissions due to human activities have grown since pre-industrial times, with an increase of 70% between 1970 and 2004". The most important of these anthropogenic GHGs is carbon dioxide (CO2).
The concentrations increased exponentially until the energy crisis in the mid-1970's rose at a rate of 1.5 ppm/year for several decades, and in the 2000s began rising at a rate of 2.0 ppm/year and higher. Every kilogram of fossil carbon burned produces about 3 kilograms of CO2 that enter the atmosphere. At least half comes from industrialized countries.
Water vapor, methane, nitrous oxide, ozone and chlorofluorocarbons (CFCS) absorb infrared radiation and add to the insulating effect of CO2. Most of these gases have anthropogenic sources and are increasing in concentration; raising the concern that future warming will extend well beyond the effects of CO2 alone.
Reference: IPCC, 2007: Climate Change 2007: Synthesis Report. Contribution of Working GroupsI, II, and III to the Fourth Assessment. Report of the Intergovernmental Panel on Climate Change (Core Writing Team, Pachauri, R.K. and Reisinger, A. (eds.)). IPCC, Geneva, Switzerland, 104 pp.