ok i learne this but i dont know how to explain it so here is what scientists think:
Many scientists do not agree with the CO2 global warming models developed by the Intergovernmental Panel on Climate Change (IPCC). For instance, T.M.L. Wigley 1, a senior scientist at the U.S. National Center for Atmospheric Research, calculated the "saved" warming that would accrue if every nation met its Kyoto Protocol obligations (U.S. reduction of 43%). By 2050, the earth�s temperature would reduce by 0.07 oC - a change so small it could not be reliably measured. In contrast to Wigley's projections, the IPCC has developed models 2 that predict the average surface temperature of the earth relative to 1980-1990, will increase by 2 to 11.5�F (1.1 to 6.4�C) by the end of the 21st century due to increased CO2 concentrations in the atmosphere. They project temperature change as functions of growth rates in atmospheric carbon dioxide.