Solar irradiance, trend

Willson, R. C. (1997). Total Solar Irradiance Trend During Solar Cycles 21 and 22. Science 277 1963-1965. 

Another potential climate forcing agent that is not well understood is solar irradiance. (This was discussed at the end of Chapter 25.4.4.) Direct measurements have been underway only since 1978 and provide no evidence for any upward trend over the past 25 or so years, although the existence of the 11-y sunspot cycle is apparent. Variations in... 

The question of longer periods of solar irradiance has been hotly debated in recent years. Such possible variations are inferred from historical records of variations in sunspots, the so-called Maunder Minimum in the late 1600 (Eddy, 1976), analogues with other sunlike stars, and paleo measurements of radioactive isotopes supposedly coupled to solar variations. Cubasch et al. (1997) forced a coupled climate model with data provided by Lean et al. (1995) as well as by Hoyt and Schatten (1993) for the period 1700 until the present. As would be expected, when the fluctuations are on a time scale of centuries or so, the model response broadly follows the forcing. The linear warming trend for the 100 years 1893-1992 is 0.19 and 0.17 K, respectively. 

Total Ozone Mapping Spectrometers (TOMS) measure solar irradiance and radiance backscattered by the earth s atmosphere at six wavelengths extending from approximately 310 to 380 nm. TOMS measurements can be used to estimate the tropospheric ozone amount by the calculation of the difference of total ozone minus stratospheric ozone amount measmed by another satellite instrument (SAGE Stratospheric Aerosol and Gas Experiment), in particular when stratospheric ozone variations are small, usually over the tropics. However, the residual tropospheric ozone calculation has some limitation in accuracy because the tropospheric ozone amount is calculated as a small difference of two large numbers (total and stratospheric ozone). Measurements of the TOMS instra-ment on Nimbus 7 satellite have been used to estimate tropical tropospheric ozone trends from 1978 to 1992. 

Basher, R. E., X. Zheng, and S. Nichol, Ozone-Related Trends in Solar UV-B Series, Geophys. Res. Lett., 21, 2713-2716 (1994). Beaglehole, D., and G. G. Carter, Antarctic Skies. 1. Diurnal Variations of the Sky Irradiance, and UV Effects of the Ozone Hole, Spring 1990, J. Geophys. Res., 97, 2589-2596 (1992). Bednarek, G J. P. Kohlmann, H. Saathoff, and R. Zellner, Temperature Dependence and Product Distribution for the Reaction of CF30 Radicals with Methane, Int. J. Res. Phys. Chem.. Chem.. Phys., 188, 1-15 (1995). 

Casale, G.R., Meloni, D., Miano, S., Siani, A.M., Palmieri, S., and Cappellani, F. (in press) Solar UV-B irradiance and total ozone in Italy fluctuations and trends, J. Geophys. Res., ECUV Special Section. 

---