"At first glance, the climate record of the past century does indeed resemble the trend in the solar output. However, because three decades of satellite data for solar heat flux (called “Total Solar Irradiance” or TSI) show only small variability it is claimed that TSI cannot explain the bulk of the energy imbalance. Solar output would therefore have to be somehow amplified in order to explain the entire magnitude of the centennial warming. The IPCC, arguing that because no amplifier is known, and at the same time the atmospheric concentrations of carbon dioxide did increase from 280 to 370 ppm, it must be the anthropogenic greenhouse gases that are responsible for most of the energy imbalance. Note that this is an assumption, an attribution by default, not an actual empirical or experimental proof that carbon dioxide is the “driver”. Such attribution is then taken as a fact and all subsequent complex model “calibrations” of climate sensitivity to CO2 are made to fit this premise. Note also that because of the overwhelming importance of water vapor for the overall greenhouse, the models would produce similar outcomes whatever the source of additional energy into the water cycle. If an amplifier to solar output does exist, and empirical observations detailed below argue for its existence, the need to attribute the energy input to CO2 would diminish accordingly."
Jan Veizer Distinguished University Professor-Geology, University of Ottawa