Unquestionably, the U.N. Intergovernmental Panel on Climate Change (IPCC) was formed to build the scientific case for humanity being the primary cause of global warming. Such a goal is fundamentally unscientific, as it is hostile to alternative hypotheses for the causes of climate change.

The most glaring example of this bias has been the lack of interest on the IPCC’s part in figuring out to what extent climate change is simply the result of natural, internal cycles in the climate system. In Chapter 9 of the latest (4th) IPCC report, entitled “Understanding and Attributing Climate Change”, you would think the issue of external versus internal forcing would be thoroughly addressed. But you would be wrong.

The IPCC is totally obsessed with external forcing, that is, energy imbalances imposed upon the climate system that are NOT the result of the natural, internal workings of the system. For instance, a search through Chapter 9 for the phrase “external forcing” yields a total of 91 uses of that term. A search for the phrase “internal forcing” yields…(wait for it)…zero uses. Can we really believe that the IPCC has ruled out natural sources of global warming when such a glaring blind spot exists?

Admittedly, we really do not understand internal sources of climate change. Weather AND climate involves chaotic processes, most of which we may never understand, let alone predict. While chaos in weather is exhibited on time scales of days to weeks, chaotic changes in the ocean circulation could have time scales as long as hundreds of years, and we know that cloud formation – providing the Earth’s natural sun shade – is strongly influenced by the ocean.

Thus, small changes in ocean circulation can lead to small changes in the Earth’s albedo (how much sunlight is reflected back to space), which in turn can lead to global warming or cooling. The IPCC’s view (which is never explicitly stated) that such changes in the climate system do not occur is little more than faith on their part.

The IPCC’s pundits like to claim that the published evidence for humanity causing warming greatly outweighs any published evidence against it. This appeal to majority opinion on their part is pretty selective, though. They had no trouble discarding hundreds of research papers supporting evidence for the Medieval Warm Period or the Little Ice Age when they so uncritically embraced the infamous “Hockey Stick” reconstructions of past temperature change.

Despite a wide variety of previous temperature proxies gathered from around the world (see figure below) that so clearly showed that centuries with global warming and cooling are the rule, not the exception, the Hockey Stick was mostly based upon some cherry-picked tree rings combined with the assumption that significant warming is a uniquely modern phenomenon.

As such, they rejected the prevailing “scientific consensus” in favor of a minority view that supported their desired outcome. I suspect that they do not even recognize their own hypocrisy.

As I have discussed before, the IPCC’s neglect of natural variability in the climate system ends up leading to circular reasoning on their part. They ignore the effect of natural cloud variations when trying to diagnose feedback, which then leads to overestimates of climate sensitivity. This, in turn, causes them to conclude that increasing carbon dioxide concentrations alone are sufficient to explain global warming, and so no natural forcings of climate change need be found.

But all they have done is reasoned themselves in a circle. By ignoring natural variability, they can end up claiming that natural variability does not exist. Admittedly, their position is internally consistent. But then, so is all circular reasoning.

Our re-submitted paper to the Journal of Geophysical Research entitled “On the Diagnosis of Radiative Feedback in the Presence of Unknown Radiative Forcing” will hopefully lead to a little more diversity being permitted in the global warming debate.

I don’t think the IPCC scientists are as opposed to this as are their self-appointed spokespersons, like Al Gore and numerous environmental writers in the media who get to over-simplify the climate issue without ever being corrected by the IPCC. Natural climate change continues to be the 800 lb gorilla in the room, and I suspect that some within the IPCC are slowly becoming aware of its existence.