http://www.salon.com/news/global_warming/index.html?story=/tech/htww/2009/11/05/climate_change_is_a_religion

You will hate this, but you really should read IPCC chapter 6
http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_Ch06.pdf
Its only one chapter and you dont have accept any of their assessments. It does however give you all the grubby detail in a much more readable format than trying to find the significant papers. It also put the papers in a context, that means if you want to be critical, you can know what went before and after. And of course, its exhaustively referenced to the papers so you can check anything.

Some comment. The ice cores are very high time resolution, better measurement of CO2 than any proxy, and state of art for temperature proxy. No proxy data comes close but of course their location makes them pretty useless of global temperature measurement. However, their resolution is so good, that it does pretty much constrain what might be global versus local events. If a temperature excursion appears at same time in both Greenland and Antarctica, then that is extremely good evidence of a global event., otherwise suspect regional.

Second, I worry about your “pure proxy” wishes – you do understand how these proxy records are created? Nonetheless, the Tingley/Huyber paper does this for you. Same basic results are other multiproxy studies though. Just be aware that it is in press and their methodology has not scrutinized by scientific community yet.

What I am after… interested to know why and how understandings of past climate (last 14,000 odd years) has changed since the first assessment report (graph that I posted earlier).

I would prefer pure proxy histories rather than a proxy-instrumental record combo, the link you posted is pure proxy so thanks on that count.

Yes understand that past climates do not prove or disprove AGW. I have actually always had an interest in history, find it interesting to understand the connection between climate and historic events. But also would like to put the current warming in a historical context.

Cheers

Figure 1 is not the temperature reconstruction. It shows that there is a non-climatic influence in one of the principal components used (ITRDB PC#1), probably from CO2 fertilisation. Look at Fig. 1 – the upper graph shows that from 1800, ITRDB PC#1 is above (i.e. warmer than) the North American Treeline (NT) series. The lower graph shows just the difference (residual) between ITRDB PC#1 and NT – you can see that it follows the CO2 quite closely for a while, and then tails off.

What this graph is showing is that ITRDB PC#1 is showing even more recent growth than the other series, because as well as responding to warmer temperatures, the trees in that series are also showing more growth due to CO2 fertilisation. If you were to treat all of that recent growth as if it were due to temperature, PC#1 would be overestimating the temperature of the 20th century

So what they did was remove the residual from the ITRDB PC#1, so that it more closely matched the NT series. If the had not removed this residual, the PC#1 series would show an even more pronounced hockey stick – and I’m sure you wouldn’t want that, would you?

Then Fig. 3 shows the final temperature reconstruction using the corrected ITRDB PC#1 – remember, this is just one of 12 series they use in the reconstruction. As I said before, the temperature reconstruction is calibrated to the temperature record, so of course the series in the calibration period matches the instrumental record. If it didn’t, it wouldn’t be much use as a proxy, now would it?

Finally, remember that there is never a final answer in science. Look at the title of the paper: “Inferences, Uncertainties and Limitations”. Mann never claimed that this was the final word, and quite explicitly says that the period before 1400 is uncertain, as the full quote shows:

Though expanded uncertainties prevent decisive conclusions for the period prior to AD1400, our results suggest that the latter 20th century is anomalous in the context of at least the past millennium. The 1990s was the warmest decade, and 1998 was the warmest year, at moderately high levels of confidence.

Several papers since then, by Mann and by others, have confirmed the hockey stick, some with different techniques. Mann’s recent paper showed that you get the same results with or without the tree-ring proxies.

But if you are determined to believe in conspiracy theories, there is no amount of scientific evidence that is ever going to change your mind.

I will say again, though that paleoclimate is hard with so much work still to do. However, unconstrained is not same as unknown. Can you reiterate for me exactly what you are looking for and why?

AGW looks to paleoclimate for constraints and hypothesis testing but it is a theory arising out of physics not geology.

http://www.ltrr.arizona.edu/webhome/aprilc/data/my%20stuff/MBH1999.pdf

Look at the paper. Look at Figure 1 the proxies. No dramatic rise at the end. Look at the final graph (figure 3): dramatic rise! Where has this come from?????? The ground based instrumental record?? Wow! So what are we saying?? What are we comparing?

Here is the article:

http://www.met.sjsu.edu/~tesfai/RESULTS/Journals/Antarctica%20warming%20nature07669.pdf

“”Antarctica is warming, and it’s warming at the same rate as the rest of the planet,” said study co-author Michael Mann of Penn State University.”

http://www.livescience.com/environment/090121-antarctica-warming.html

As with MBH98 this is an astounding revelation. A paper has claimed that what everyone else held true, is wrong! This does not make the paper false of course. But a sceptic will always look at this new discovery with a critical eye.

I am not sure to be honest on the merit of this paper. It claims a 50 year warming trend.

This paper claims a current increase:
“We show that 72% of the Antarctic ice sheet is gaining 27 +/- 29 Gt / yr, a sink of ocean mass sufficient to lower global sea levels by 0.08 mm / yr″

http://www.cpom.org/research/djw-ptrsa364.pdf

In response to the Antarctic paper, “A disbelieving Ross Hayes, an atmospheric scientist who has often visited the Antarctic for Nasa, sent Professor Steig a caustic email ending: “with statistics you can make numbers go to any conclusion you want. It saddens me to see members of the scientific community do this for media coverage.”"

So whats my point here? I do not know the truth(and I am not trying to start a debate on the Antarctic). But given the controversy surrounding much of his work I can not help but raise my eyebrows when the only references people can find come from Real Climate and Michael Mann. I think if there was one predominant author who repeatedly published papers that cast doubt on AGW theory you would be skeptical also? (as would I). You would want to see other sources to reconcile the claims?

” The “Hockey Stick” studies claim that the 20th century on the whole is the warmest period of the past 1000 years.” which talks a little around the problem of what proxies can show. Crowley’s paper and Rutherford’s also illuminating since you clearly have some misconceptions about how proxies are constructed.

However, I am left in a quandary. You are obviously impressed by Bookers uninformed rave but dont trust the work of climate scientists? This makes it very difficult to have a discussion. You have trouble following the actual papers, you dont like explanatory pieces about the science (the are NOT opinion pieces) if they are written by climate scientists because climate scientists are AGW advocates (reality advocates would be better) and yet trust looney tunes stuff in a opinion piece from someone who is clearly clueless about the science.

If we cant present science papers as evidence, then how do we proceed? If you want your questions answered, then I will do my best but that must happen in the context science and data.

Let me see if I can recap because I think the argument got lost somewhere along away as it wondered into paleoclimate. Is current era unique? Well depends on timeframe. Is it different from LIA,MWP type events – yes. Firstly its not regional, and second explain say the Tasman glacier position. Are we beyond ice ages. Now thats a more tricky question. The milankovitch cycles which drive the ice ages were still working even when CO2 was high enough that we had no ice caps. Once planetary temperature dropped to point where ice formation at the poles was possible then this allowed for albedo feedbacks to kick in. Without feedback, the forcings from milankovich cycles would still have had some effect on climate but very small. I would say that you break the ice age cycle when+ve GHG forcings is greater than -ve TSI forcing. I’d say that paleoclimate data for what the world looked like with 450ppm CO2 is pretty ugly re: ice cap though greenland and East Antartica would take in order of 1000 year to melt.

Disclosure: I am geoscientist working in hydrocarbons section. If the world lost interest in oil/gas/coal our section would cease to get funding.