Well, that and what the proper response should be. Some proponents of AGW have taken on a harsh anti-capitalist look. I think many people who call themselves sceptics are simply sceptical of the fact that, suddenly, there is a new castastrophe that can only be solved by adopting the very same economic policies that these same people have been pushing for decades.

And, on that note, Roy Spencer has spoken of “intelligent design” in sympathetic tones, contrasting this with “evolutionism”. He has said:

“I finally became convinced that the theory of creation actually had a much better scientific basis than the theory of evolution, for the creation model was actually better able to explain the physical and biological complexity in the world.”

These are the words of a man who clearly has no understanding of the scientific theory of evolution by natural selection. If you’re asking if I take him seriously, the answer is no, I do not.

The words of Spencer quoted above are largely content free, and begin with a statement which simply isn’t true. The analysis of complex systems is a challenging pursuit, but categorical statements such as that made by Spencer cannot be justified. He is also misrepresenting the IPCC scientists who contributed to the AR4 report.

The problem, when it comes to the public’s understanding of the Earth’s climate, is that climate change deniers and so-called “sceptics” are addressing themselves to an almost exclusively lay audience – i.e., they are putting the climate science community on trial in the court of public opinion, and, given the way the media and polity work, one denier can have the same public influence as a large number of research-active experts.

Deniers and sceptics employ tried and tested rhetorical devices to shift the goal posts when their arguments are shown up for what they are, and have no shame in distorting science for ideological ends.

For example, Roy Spencer had a post the other day which left me feeling uncertain.

Despite the fact that the magnitude of anthropogenic global warming depends mostly upon the strengths of feedbacks in the climate system, there is no known way to actually measure those feedbacks from observational data.

The IPCC has admitted as much on p. 640 of the IPCC AR4 report, at the end of section 8.6, which is entitled “Climate Sensitivity and Feedbacks”:

“A number of diagnostic tests have been proposed…but few of them have been applied to a majority of the models currently in use. Moreover, it is not yet clear which tests are critical for constraining future projections (of warming). Consequently, a set of model metrics that might be used to narrow the range of plausible climate change feedbacks and climate sensitivity has yet to be developed.”

Comparing scientific methodology with some idle thoughts thunk up by some tortured soul during an extended lunch is more than a bit unfair.

Bit unfair, I know, but just saying. “Reduction in uncertainty” is nothing to boast about.

The little ice age was a less than one degree cooling of the northern hemisphere, relative to late 20th century levels, with particularly cold snaps confined to particular regions. Regional variations such as this are in large part due to changes in atmospheric and oceanic circulation.

As for the modern day, we have temperature sensors everywhere across the planet, including radiometers aboard Earth-observing satellites that give us ocean surface temperatures to 0.1 degree accuracy. Putting together a global average temperature is a complex, statistical process, but one well understood and reliable.

Conversely, how do we know the current data are global not regional?

Yes; observed climate change cannot be explained otherwise, given our understanding of atmospheric and oceanic physics and chemistry. Natural variations are smaller in scale, and much slower than what we are observing.

The Mediaeval warm period and mini ice age were regional, not global phenomena, and are thus irrelevant.

Do you think it’s settled that man-made carbon is definitely affecting temperature?

Or are you making the more urgent point that the above is true and that this will lead to dangerous rises in temperature?

I’m a historian by training and the layman’s problem that I have with the global warming case is that, at least in this country, the wine-producing warmth of the medieval period and the mini-ice age of the 16th century both pre-date carbon emissions. Why should temperature changes have a different cause this time and also be so much more dangerous for us?

I do realise this debate is being conducted pretty much permanently somewhere on the internet but it would be nice to read something from a known and trusted source!