Climate models predict that the emission of greenhouse gases into the atmosphere has altered the radiative energy balance at the earth's surface by several percent through increasing the greenhouse radiation from the atmosphere. With measurements at high spectral resolution, this increase can be quantitatively attributed to each of several anthropogenic gases. An energy flux imbalance of about 3 W/m2 has been created by anthropogenic emissions of greenhouse gases of which we have measured almost 1.0 W/m2.
Calibrated spectra of the greenhouse radiation from the atmosphere have been measured at ground level from Peterborough using an FTIR with a resolution of 0.1 wavenumbers. This long wave radiation consists of thermal emission from naturally occurring gases such as CO2, H2O and O3 as well as from many trace gases such as CH4, CFC11, CFC12, CFC22 and HNO3. The forcing radiative fluxes from CFC11, CFC12, CCl4, N2O, CH4 and CO2 have been quantitatively measured. The greenhouse radiation fluxes from the various gases have been computed with the radiation code from the NCAR community model for the location and seasons of the measurements. Overall the agreement in most fluxes is good, providing increased confidence in the NCAR GCM. Similar comparisons of our experimental measurements with simulations using the column model from the Canadian GCM are in progress.