Shortwave radiation from the sun is the prime energy source driving temperature at Earth's surface. Climatological conditions that foster live on Earth however, are only reached with atmospheric greenhouse gases absorbing and reemitting thermal longwave radiation back to the surface, thereby acting as second energy source elevating the surface temperature on average by 33°C. The atmospheric greenhouse effect and its relation to temperature and humidity is investigated by studying the individual radiative fluxes. Consider the following relations:

• Surface temperature is directly related to absorbed shortwave and longwave radiation
• Surface reflection of shortwave radiation (albedo) is cooling the surface
• Clouds modulate radiative fluxes and temperature by shortwave cooling and longwave warming
• Aerosols scatter and absorb shortwave radiation, cooling the surface but heating the atmosphere
• Greenhouse gases absorb and reemit longwave radiation and increase the temperature
• Water vapor is the most abundant greenhouse gas and increases with temperature.

The investigations are based on accurate measurements of downward and upward shortwave and longwave radiative fluxes at screen level height ( 2 meter above surface ) at ten stations of the Alpine Surface Radiation Budget (ASRB) network. ASRB stations are colocated with MeteoSwiss automatic meteorological stations and are distributed between 370 and 3580 m a.s.l. and over an area of about 200 by 200 km2 in the Alps (central Europa, latitude ~ 46°N).