Measurement and uncertainty of the long-term total solar irradiance trend

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).