In 2001, the Intergovernmental Panel on Climate Change (IPCC), in their "Summary for Policymakers" showed the cooling -- yes, cooling -- effects of human activity.
Granted, humans burn fossil fuels releasing CO2, domesticated animals release methane gas, and we release Freon and other industrial chemicals that contribute to climate warming.
But humans also create aerosols of various sorts. Aerosols are small particles that stay airborne and affect the properties of the atmosphere. Note this section of a chart from the 2001 IPCC report that identifies aerosols that can cause both warming (in the pink area, black carbon and mineral dust) and cooling (in the blue section, sulphate, organic carbon, biomass burning, and indirect effects). What are the indirect effects of small particles floating in the atmosphere? They tend to cause cloud formation, and clouds reflect solar energy away from the earth, thus cooling the planet by shading the earth from the hot, hot sun.
Therefore, not every activity of man contributes to global warming. Aerosols contribute to global cooling, and therefore they offset the warming of our carbon dioxide and other greenhouse gas emissions. Have you heard this discussed in your newspaper? newsmagazine? television news report? talk radio? It is unlikely you have. Not only is the IPCC ignoring the data in their own report, almost everyone else seems oblivious to the implications as well.