It is believed that the radiation budget of the Earth-atmosphere system plays a fundamental role in determining the thermal conditions and the circulation of the atmosphere and the ocean, shaping the main characteristics of the Earth's climate. The irradiances at the Earth's surface are especially important in understanding the climate processes, since the Earth's surface transforms approximately 60% of the solar radiation absorbed by the planet. These irradiances also occupy an important position in the ocean surface energy budget, ultimately influencing the major features of ocean currents. While a small change in irradiance at the Earth's surface may cause a profound change in climate, the existing radiometric network is not capable of arriving at the required accuracy for climate research. In fact our present understanding of the radiation distribution both - horizontally and vertically - is not sufficient to understand the present climate. The simulation of the past and future climate changes, which would be induced by the change in radiation, is even more uncertain. This was the background for the World Climate Research Programme (WCRP) Radiative Fluxes Working Group to initiate a new Baseline Surface Radiation Network (BSRN) to support the research projects of the WCRP and other scientific programs. Some years later the BSRN incorporated into the WCRP Global Energy and Water Cycle Experiment (GEWEX).