Radiation from the sun

Solar radiation to the earth has been measured from satellites since 1978. "Total Solar Irradiance" (TSI) includes all wavelengths from shortwave ultraviolet radiation to longwave radiation. It is measured in W/m² and the value varies around an average of 1361 W/m² [L4]. Different types of measuring instruments and satellite platforms have been used during this period, and each instrument has had its individual systematic errors. This is clearly shown in the following figure taken from [L5]:

The different measurement series in this figure partially overlap, and this has made it possible to assemble one consecutive time series where systematic errors in each measurement series have been removed (or at least "normalised" to the same level). Such a continuous series is shown in the following figure, taken from [L4]:

This figure clearly shows a cyclical variation in the TSI with a period of approxmately 11 years. From about 2007, a declining trend is visible, which is particularly reflected in a lower peak in the last cycle. This should indicate a cooling effect, or at least no heating due to the sun.

Latest update: 2021-07-10