On his October 12 broadcast, Newsradio 850 KOA's Mike Rosen repeated the discredited claim that "[s]olar activity over eons has been the principal influence on climate change on this planet." As Colorado Media Matters noted after Rosen made this claim during his September 19 broadcast, the argument that the sun -- rather than human activity -- is primarily responsible for current climate change echoes a conservative talking point that rejects overwhelming scientific consensus, including the 2007 report of the United Nations Intergovernmental Panel on Climate Change (IPCC).

As Colorado Media Matters has documented, Rosen has promoted this and other misinformation about global warming on numerous broadcasts.

Rosen made his statement about the influence of solar activity on climate change after the Norwegian Nobel Committee announced on October 12 that former vice president Al Gore and the IPCC would share the Nobel Peace Prize for 2007 “for their efforts to build up and disseminate greater knowledge about man-made climate change, and to lay the foundations for the measures that are needed to counteract such change.” During a discussion with a caller about a program on climate change that she had viewed on the National Geographic Channel, Rosen said, “I think it's a great conceit that human activity is a major player in this regard.”

From the October 12 broadcast of Newsradio 850 KOA's The Mike Rosen Show:

CALLER: I saw a special this summer on the National Geographic Channel and it was put out by National Geographic. It was on how the sun is heating up, and that all stars heat up as they age.

ROSEN: Mm-hmm.

CALLER: And they went into accounting for all of the so-called global warming trend connecting it into the sun. They also went into how a volcano does a lot more damage than people ever hope to do.

ROSEN: Like Mount St. Helens, for example.

CALLER: Right.

ROSEN: Mm-hmm.

CALLER: And, you know, we can't put that much carbon out if we wanted to.

ROSEN: I agree. I think it's a great conceit that human activity is a major player in this regard. But there are a lot of people who desperately want to believe this great conceit and then bend you to their will, and bend industry to their will, and force everybody to change their behavior patterns -- which, incidentally, achieves some other objectives of theirs that has nothing to do with climate change

CALLER: True.

ROSEN: So I just -- sorry, I don't buy it.

CALLER: I don't either.

ROSEN: Solar activity over eons has been the principal influence on climate change on this planet. We've had warming periods, we've had cooling periods, we've had ice ages long before there were humans driving SUVs. And that's likely to continue in the future. And by the way, who's to say our current climate is the optimal climate? It just happens to be what the climate is now. Who's to say that two or three or four degrees of warming won't be better?

Contrary to Rosen's assertion that "[s]olar activity over eons has been the principal influence on climate change on this planet," the IPCC's 2007 report found that "[t]he rapid warming observed since the 1970s has occurred in a period when the increase in greenhouse gases has dominated over all other factors." The report further stated, “The human influence on climate very likely dominates over all other causes of change in global average surface temperature during the past half century.” Specifically addressing the possible contributions of solar activity to warming, the report concluded:

It is extremely unlikely (<5%) that the global pattern of warming during the past half century can be explained without external forcing, and very unlikely that it is due to known natural external causes alone. The warming occurred in both the ocean and the atmosphere and took place at a time when natural external forcing factors would likely have produced cooling.

Greenhouse gas forcing has very likely caused most of the observed global warming over the last 50 years. This conclusion takes into account observational and forcing uncertainty, and the possibility that the response to solar forcing could be underestimated by climate models. It is also robust to the use of different climate models, different methods for estimating the responses to external forcing and variations in the analysis technique. [emphasis in original]