-  CO2 is the major contributor to global warming, the warming 
  effect over the next 100 years of current emissions of greenhouse gases will
   depend upon the amount of each gas being delivered globally and its global warming potential, GWP. 
   The GWP is the warming effect of an extra 1kg of a greenhouse gas emitted today, relative to 1kg
    of CO2.
- The results of the calculation are shown in this slide.  CO2 will be responsible for about two thirds of the expected future warming.
  
Source: Hadley Centre for Climate Prediction and Change.