I don't know about AGW
but I'm a little skeptical that we've had that much impact on the climate. It's certain that things are changing- but what of that? Why should it stay constantly the same? Who's to say that the climate we've known for the past fifty years is the optimal climate for anything?

A key concept that I have yet to see addressed: how do we demonstrate that someone's climate model is correct? I would think that the best way would be to feed it raw data up to 1990 and see if it can predict what actually happened over the next two decades. If it's close, it's worth using. If it's drastically off, it's a pile of wank.

I find Jerry Pournelle's response intriguing. In brief, he points out that we should spend some time and effort on figuring out eactly what is changing before we start making laws based on what we fear might be happening.

There is a good summary of what is known and what is not known about Climate Change models by MIT Meteorology professor Robert Lindzen in today's Wall Street Journal.
online.wsj.com/article/
SB10001424052748703939404
574567423917025400.html

It's a good introduction to what's serious about ClimateGate.

The notion that complex climate "catastrophes" are simply a matter of the response of a single number, GATA, to a single forcing, CO2 (or solar forcing for that matter), represents a gigantic step backward in the science of climate.

GATA is the globally averaged temperature anomaly. It is the single figure of merit that governs the concern about climate change and global warming, and the real truth is that it can't be measured to the kind of accuracy demanded by the climate change/global warming hypothesis. Debates about the wisdom of governing multi-billion dollar economic decisions on the basis of a single figure of merit are certainly not inappropriate at the policy level; and debates about the reliability of that figure of merit are certainly appropriate in scientific journals. Note that those who advocate those debates are generally denounced as "deniers", and the Climategate Papers suggest strongly that political tactics, not scientific concern, have been the moving issue in much of the UN IPCC reports. Lindzen clarifies this. If you haven't read his paper, it's worth your time to go read it now.

Lindzen summarizes the science, and in an aside says that perhaps the worst crime of the IPCC conspirators as revealed by the Climategate Papers is "their destruction of raw data". We can all agree to that. Do note that the raw data cannot possibly generate a consensus GATA accurate to fractions of a degree. The data aren't that good.

Much of the raw data have been deleted, but some general observations remain. I've mentioned this before, but it's worth reminding ourselves of some things we all know.

The Earth has been much warmer in historical times. We have some general ideas about climate in ancient and classical times, but we needn't go back that far: we all know about the Medieval Warm period. We all know that the Vikings established dairy farms in Greenland. Some of those farms are emerging from glacial ice, but some remain covered. We all know from Doomsday Book that there were vineyards in northern England in the time of William the Conqueror. It's less well known that there were vineyards in Scandinavia and Scotland, but that's easy to establish. We have records of growing seasons from those times from both Europe and China. Protests that the Greenland Viking farms were due to some strange wandering of the Gulf Stream are merely assertions: neither evidence for those wanderings nor mechanisms for accomplishing them are backed with serous evidence. It was just plain warmer from about 800 AD, and that continued until about 1325 when climate changed rather dramatically with a year of dark and cold rain, and it began to get colder. The exact GATA of the Medieval Warm period isn't agreed -- how could it be? -- but that the Earth was warmer then is simply not in doubt, nor is there anything like a consensus on just why we had that warming. It was a significant fact in both Western and Chinese history -- food was more abundant, populations grew, travel was easier -- and the effects seem to have been positive.

We know that the Earth has been much colder in historical times. My favorite example is that the cannon of Ticonderoga, captured by Ethan Allen and the Green Mountain Boys ("by the authority of the Great Jehovah and the Continental Congress!") and dragged across New England by Henry Knox. Rivers froze solid enough to drag cannon across them. We have other indications of temperatures from 1700 to 1800. It was cold. Rivers froze. Growing seasons were shorter than now. We have similar data for Europe and China. Recall Hans Brinker and the Silver Skates and skating contests on the frozen brackish canals of Holland. Again we have no reliable (to a degree, much less to fractions of a degree) estimations of GATA, but we can all agree that it was considerably colder.

We know that temperatures began slowly to rise sometime after 1800 (there was so far as I know no dramatic event) and the trend was obvious after about 1825. Growing seasons grew longer. Rivers that formerly froze solid became unreliable. Spring icebreaks came earlier, and streams froze later. Cuckoos nested earlier. Those trends continued into the Twentieth Century, and may be continuing now.

We know that the major climate alarm in the 1970's and early 1980's was the fear of a coming Ice Age. Gus Spaeth, Carter's environmental quality advisor, was concerned that nuclear waste depositories be able to withstand glaciation. Margaret Meade as President of AAAS had much to say about the coming bad times as the world began cooling. During the 1980's the speculations of Arrhenius made about 1895 about possible "greenhouse" effects of CO2 began pushing forward, and with increasingly powerful (and cheap) computers climate models became affordable to many academic and scientific institutions. The models began predicting warming, although the data collectors weren't really finding it. The rest is history. There emerged a "consensus" about an "inconvenient truth". Whether that consensus was forced by scientific data or by social engineering is open to question.

Finally we know that one phenomenon of the coldest part of the Little Ice Age was the "Maunder Minimum": a long period of minimal solar activities, characterized by long periods of few to zero sunspots. You can monitor rcent solar activity at www.solarcycle24.com/ .

Given that the science is not settled, and that the economic effect of national policy to counter "climate change" are enormous, simple Bayesian analysis would indicate that we ought to be spending a lot of money to determine just what the climate trend is: and that means funding contrarian studies, studies designed to refute the "consensus" theory, as well as funding the collection of accurate data. This seems an obvious conclusion. It is of course inconvenient to those whose careers have been financed by grants peer reviewed by peers who don't include "deniers."
( The Resident Loon Not a demographic. Do not measure., Wed 2 Dec 2009, 14:12, Reply)