Baby it's warm outside
...Then, noting that the IPCC (2001) suggested that the increase in anthropogenic radiative forcing over the 20th century was about 0.5 Wm-2, Shaviv calculated that the anthropogenic-induced warming of the globe over this period was approximately 0.14°C (0.5 Wm-2 x 0.28°C per Wm-2). ...
Next, based on information that indicated a solar activity-induced increase in radiative forcing of 1.3 Wm-2 over the 20th century .., plus the work..that indicated a globally-averaged solar luminosity increase of approximately 0.4 Wm-2 over the same period, Shaviv calculated an overall and ultimately solar activity-induced warming of 0.47°C (1.7 Wm-2 x 0.28°C per Wm-2) over the 20th century. Added to the 0.14°C of anthropogenic-induced warming, the calculated total warming of the 20th century thus came to 0.61°C, which was noted by Shaviv to be very close to the 0.57°C temperature increase that was said by the IPCC to have been observed over the past century. Consequently, both Shaviv's and Idso's analyses, which mesh well with real-world data of both the recent and distant past, suggest that only 15-20% (0.10°C/0.57°C) of the observed warming of the 20th-century can be attributed to the concomitant rise in the air's CO2 content.
In light of these real-world-based observations, plus the multitude of studies that indicate most climate changes of the past were clearly associated with changes in solar activity (see Solar Effects in our Subject Index), the case for anthropogenic CO2 emissions playing anything more than a minor role in contemporary global warming would appear to be fading fast.
Hat tip CCNet