Empirical analysis of the solar contribution to global mean air surface temperature change. Journal of Atmospheric and Solar-Terrestrial Physics (2009), doi:10.1016/j.jastp.2009.07.007 By Nicola Scafetta, Department of Physics, Duke University, Durham, NC 27708, USA
Abstract
The solar contribution to global mean air surface temperature change is analyzed by using an empirical bi-scale climate model characterized by both fast and slow characteristic time responses to solar forcing. Since 1980 the solar contribution to climate change is uncertain because of the severe uncertainty of the total solar irradiance satellite composites. The sun may have caused from a slight cooling, if PMOD TSI composite is used, to a significant warming (up to 65% of the total observed warming) if ACRIM, or other TSI composites are used. The model is calibrated only on the empirical 11-year solar cycle signature on the instrumental global surface temperature since 1980. The model reconstructs the major temperature patterns covering 400 years of solar induced temperature changes, as shown in recent paleoclimate global temperature records.
Some excerpts:
“DETERMING how solar activity has changed on decadal and secular scales is necessary to estimate the solar contribution to climate change. Unfortunately, how solar activity has changed in time is not known with certainty.
“Direct TSI observations started in 1978 with satellite measurements. For the period before 1978 only TSI proxy reconstructions have been proposed. These TSI proxy models significantly differ from each other, in particular about the amplitude of the secular trends.
“Unfortunately, TSI satellite composites since 1978 are not certain either. Two major composites have been proposed: the PMOD TSI composite which shows an almost constant trend from 1980 to 2000; and the ACRIM TSI composite which shows an increasing trend during the same period. GCMs and EBMs adopted by
the IPCC (2007) assumed that TSI did not change significantly since 1950 and that, consequently, the sun could not be responsible for the significant warming observed since 1975.
“These estimates are based on TSI proxy models such as those prepared by Lean (2000) and Wang et al. (2005) which are apparently supported by PMOD. However,
the above TSI proxy models would be erroneous if the ACRIM TSI composite more faithfully reproduces the TSI behavior during the last decades.
(bolded is mine)
Cheers.