Remote Sensing Measurements of Greenhouse Gas Radiative Fluxes

摘要

A technique for the remote sensing of the forcing function of global warming (i.e., the increase in the surface radiative forcing) is described. Climate models predict that the emission of greenhouse gases into the atmosphere has altered the radiative energy balance at the earth's surface through increasing the greenhouse radiation from the atmosphere. With measurements at high spectral resolution, this increase can be unambiguously attributed to each of several anthropogenic gases. Calibrated spectra of the greenhouse radiation from the atmosphere have been measured at ground level from Peterborough, Ontario using an FTIR spectrometer with-a resolution of 0.1 cm~(-1). This long-wave radiation consists of the thermal emission from naturally occurring gases, such as CO_2, H_2O and O_3, as well as from many trace gases, such as CH_4, CFC11, CFC12, CFC22 and HNO_2. The forcing radiative fluxes from CFC11, CFC12, CCl_4, N_2O, CH_4, HNO_3 and CO_2 have been quantitatively measured. Measurements of the fluxes associated with each gas are presented. Models indicate that an energy flux imbalance of about 3 W/m has been created by anthropogenic emissions of greenhouse gases of which we have measured over 1.0 W/m~2. Much of the remaining flux change is due to CO_2 and CH_4 increases which are difficult to measure without a long baseline data series. Overall, it has been demonstrated that the greenhouse radiation is measurable and it should be monitored on a worldwide basis over the long term since the predicted increase in this energy flux is the fundamental forcing of global warming.