However, climate models are programmed with solar forcing that is 5-13 times less than found by state-of-the-art solar activity reconstructions. For example, the NASA-GISS climate model uses the following solar forcing assumption:
which shows solar activity increased during the 20th century by only about 0.15 Watts per meter squared [W/m2]. Contemporary solar activity reconstructions, however, show that solar activity increased during the 20th century by 1.5 - 4 W/m2 or 10 - 26 times more than assumed by the NASA-GISS model. If one assumes 30% albedo and divide by four [an incorrect and simplistic assumption as demonstrated by Joe Postma], the GISS model uses up to ~5 times less solar forcing anomaly change in comparison to solar proxy data.
|Reconstructed Total Solar Irradiance [TSI] shown in upper right graph shows an increase of ~ 4 W/m2 over the 20th century
In addition, since solar forcing was much higher than assumed by the models, this implies that CO2 forcing was significantly less than assumed by the models.