This figure from Scafetta 2009 demonstrates the uncertainty surrounding what Solar Irradiance has done over the last 30 years.http://www.sciencedirect.com/science/ar ... 2609002089
If the ACRIM reconstruction were to be correct, then most of the warming could be explained by solar irradiance alone over the last 30 years.
The rest of the warming could be due to many things, including Cloud Cover changes, Volcanism, contribution from the PDO/AMO, and contributation from CO2.
However, if the PMOD reconstruction is to be used, there would be little to no contributation by TSI over the last 30 years.
Cloud Cover would then probably have more of an impact, and be the driving force of Climate Change over the last 30 years, with CO2 being a minor contributor. This is because many papers have documented a significant increase in ISR over the last 30 or so years reaching Earth's Surface, so a natural component is necessary to explain the warming in the late-20th Century. Whether it's Solar Irradiance or Cloud Cover Changes (or both) is yet to be determined, but many papers have found that the increased ISR correlated strongly to the Cloud Radiative Forcing, meaning Cloud Cover is at least partially responsible for the increased ISR reaching Earth's Surface. If both Cloud Cover decreased and TSI increased, then nearly all of the warming can be attributed to natural factors.
Dr. Willson and Dr. Scaffeta have a paper on this discrepency, and concluded that PMOD may be suffering from errors within the data, explaining why there is no trend in the power of the minimums of SC 21 and 22.http://www.fel.duke.edu/~scafetta/pdf/2008GL036307.pdf
From the conclusions:
This finding has evident repercussions for climate change and solar physics. Increasing TSI between 1980 and 2000 could have contributed significantly to global warming during the last three decades [Scafetta and West, 2007, 2008]. Current climate models [Intergovernmental Panel on Climate Change, 2007] have assumed that the TSI did not vary significantly during the last 30 years and have therefore underestimated the solar contribution and overestimated the anthropogenic contribution to global warming.
Dr. Willson and Dr. Mordinov discuss possible problems with PMOD in their 2003 paper:http://www.acrim.com/Reference%20Files/ ... 23%20(2003
The absence of a minima-to-minima trend in the
PMOD composite is an artifact of uncorrected ERBS
degradation. ERBS degradation during the gap equals the
trend difference and the PMOD offsets (within computational
Scientists associated with ACRIM:http://www.acrim.com/staff.htm
This uncertainty needs to be resolved before the "consensus" on Climate Change can become legitimate.