A new instrument, GERB, is now operating on the European Meteosat-8 spacecraft, making unique, accurate, high-time-resolution measurements of the Earth's radiation budget for atmospheric physics and climate studies.

A possible long-term trend of the total solar irradiance could be a natural cause for climate variations on Earth. Measurement of the total solar irradiance with space radiometers started in 1978. We present a new total solar irradiance composite, with an uncertainty of ± 0.35 W m −2 . From the minimum in 1995 to the maximum in 2002 the total solar irradiance increased by 1.6 W m −2 . In between the minima of 1987 and 1995 the total solar irradiance increased by 0.15 W m −2 .

[1] The Differential Absolute Radiometer is making measurements of the total solar irradiance as part of the Variability of Irradiance and Gravity Oscillations experiment on the Solar and Heliospheric Observatory. We present the measurements made during its 7.8 years of operation, from 1996 until the present (2003). The aging due to UV exposure of the continuously measuring left channel is determined by comparison with the backup right channel; the loss in sensitivity of the left channel is 0.5 W/m 2 or 364 ppm over 7.8 years. A raise of the total solar irradiance from a level of 1365.5 W/m 2 at the end of the solar minimum in 1996 towards a maximum level of 1368 W/m 2 at the beginning of 2002 has been measured by DIARAD.

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