There is only one goddess Gaia and Al Gore is her only prophet...

[Jester]

From Craig Loehle,<blockquote>“There are reasons to believe that tree ring data may not capture long-term climate changes (100+ years) because tree size, root/shoot ratio, genetic adaptation to climate, and forest density can all shift in response to prolonged climate changes, among other reasons.” Furthermore, Loehle notes “Most seriously, typical reconstructions assume that tree ring width responds linearly to temperature, but trees can respond in an inverse parabolic manner to temperature, with ring width rising with temperature to some optimal level, and then decreasing with further temperature increases.” Other problems include tree responses to precipitation changes, variations in atmospheric pollution levels, diseases, pest outbreaks, and the obvious problem of enrichment that comes along with ever higher levels of atmospheric carbon dioxide. Trees are not simple thermometers!</blockquote> More here on why divergence is a huge issue with tree rings. Or, an article by Loehle "A 2000-Year Global Temperature Reconstruction Based on Non-Treering Proxies" where he describes issues with tree ring proxies. Notice the absence of a hockey stick.

Okay. Realclimate has analysis of that one too. (And, unsurprisingly, Lubos Motl has criticisms of the criticisms.) Probably also worth looking into Ammann and Wahl, who claim to have more or less replicated Mann's big picture, although not quite as starkly like sports equipment.

But, even if we take that meta-reconstruction as gospel, tossing out every other reconstruction showing lower variance in the past, we're still looking at an enormous rise in modern temperatures from any point in already almost matching the top of the putative MWP - the difference is not significant. That leaves denialists with the "it's been this way before" argument and AGW proponents with the "well, yeah, but why is it this way *now*" rebuttal. If CO2 is a primary driver (and I've not seen anything convincing that suggests otherwise, though I'm hardly a climatologist), then it's interesting, but far from conclusive, what happened a thousand years ago - the thing to test is the sensitivity of the climate to what we're doing today. Thankfully, AGW gives a very strong prediction - we expect global temperatures to continue rising within the bounds of the trends-plus-noise. Any other result is inconsistent with the model.

And, other measures can give us glimpses of earth's climate history, however, I've only seen one model that has been accurate in predicting the past 15 years of climate, and it was based on oceanography and CO2 was not a factor. This paper by William M. Gray, a meteorologist, presented at 21st NOAA Climate Workshop, Huntsville, AL (1996). But, er, Blasphemy!!!

Blasphemy is not a problem, but being wrong is. That paper was written in 1996. Two years later is the single warmest year on the instrumental temperature record, and current temperatures are still warmer than 1996, not cooler as predicted by that paper.

That said, I'm open to the idea of AGW, but the science needs to be compelling.

What you say of AGW, I'll say of your openness: I'll believe it when it looks compelling.

So far, it seems to be more smoke, mirrors, and wishful thinking (and perhaps some creative programming). I've said this before... Burning fossil fuels and pumping pollutants, and even CO2 cannot be a good thing for our ecology, so if and when we can move to a clean abundant source of energy, then we should do it. This is common sense, not science. I expect science to catch up to the common sense someday and prove me correct.

Common sense dictates that pumping historically unprecedented levels of greenhouse gases into our atmosphere without limit is going to cause long-run warming - look at Venus for the absurdly extreme example. The questions are about rates and non-linearity and all sorts of stuff, but the basic prediction is as common sense as it gets. Whether common sense is of any help here is another question.

However, if you're in agreement with reducing CO2 pollution to any meaningful extent, then surely it must trouble you that not only are levels increasing, but rates? We're putting *more* into the atmosphere than ever before, and unless we follow the advice of someone like Al-Gore-Who-You-Dislike-So-Much, that's not going to change until we've burned the last gram of fossil fuel. How does that square with your "common sense"?

-Jester