The Earth's Radiation Budget from Space: Detecting Climate Change".

     Abstract:       

The radiative energy balance between absorbed shortwave (SW) and emitted longwave (LW) radiation at the top of the Earth's atmosphere includes the fluxes of energy that drive and respond to the Earth's climate system.  Measurements of both spectrally resolved, and spectrally integrated, radiances and fluxes have been made from spacecraft since the 1970's, and we are now able to address some important and fundamental questions, such as:

                * Is the Earth in equilibrium?
                * Do departures from equilibrium occur, and if so with what time constant do they relax back to equilibrium?
                * Can we throw light on the natural, internal variability of the climate system?
                * Against the background of natural variability, can we detect climate change through analysis of the trends in integrated flux, or in spectral radiances?
                
                In this talk, we will introduce the subject of satellite measurements of radiation components, and present some of the data which we at Imperial College have used to study climate variability and trends. New results will be presented, including the first observation of a change in the greenhouse forcing of the Earth has indeed changed in response to growth in greenhouse gases.