evidence: While a ton-for-ton comparison of emissions is useful, it is more helpful to understand the overall influence each type of emission has on climate change. The best method to compare the total effect of very different climate pollutants is radiative forcing. This measures the change in Earth’s energy budget (i.e., the warming effect) caused by the total atmospheric concentration of a GHG or particulate. The radiative forcing of CO2 (over pre-industrial conditions) is 1.66 watts per square meter (W/m2)*. Methane’s radiative forcing is 0.48 W/m2. In other words, the current atmospheric concentration of methane causes a warming effect equal to 29 percent of the effect caused by the current concentration of CO2. *Radiative forcing measures the change in energy, in watts, at the top of the atmosphere averaged over each square meter of the planet. Emissions that have a cooling effect, such as sulfates, have a negative radiative forcing.