Last time we went through something like this you humiliated yourself when it became obvious you'd never set eyes on the original documents. Want to try it again?

From the NAS Report, on the "Mann Hockey Stick" curve:

Later, Mann and Jones (2003) extended the multiproxy reconstruction further back to cover the last 1,800 years (see Figure 10-4). On the basis of these reconstructions, it was concluded that temperatures gradually dropped from a relative maximum at about A.D. 1000 to a minimum at about 1850 and then increased sharply through the 20th century. The graph illustrating the trend, often called the hockey stick curve (reproduced in Figure O-4), received wide attention because it was interpreted by some people as definitive evidence of human-induced global warming. The ensuing debate in the scientific literature continues even as this report goes to press (von Storch et al. 2006, Wahl et al. 2006).

The Mann et al. large-scale surface temperature reconstructions were the first to include explicit statistical error bars, which provide an indication of the confidence that can be placed in the results. In the Mann et al. work, the error bars were relatively small back to about A.D. 1600, but much larger for A.D. 1000–1600. The lower precision during earlier times is caused primarily by the limited availability of annually resolved paleoclimate data: That is, the farther back in time, the harder it is to find evidence that provides reliable annual information. For the period before about A.D. 900, annual data series are very few in number, and the non-annually resolved data used in reconstructions introduce additional uncertainties.

The NAS report itself is reasonable, and has the proper caveats and cautions. It's the press and the political priesthood of global warming making the human-caused warming apocalypse into a certainty that science isn't ready to back up.

Another series of conclusions from the report:

• The instrumentally measured warming of about 0.6°C during the 20th century is also reflected in borehole temperature measurements, the retreat of glaciers, and other observational evidence, and can be simulated with climate models.

• Large-scale surface temperature reconstructions yield a generally consistent picture of temperature trends during the preceding millennium, including relatively warm conditions centered around A.D. 1000 (identified by some as the “Medieval Warm Period”) and a relatively cold period (or “Little Ice Age”) centered around 1700. The existence and extent of a Little Ice Age from roughly 1500 to 1850 is supported by a wide variety of evidence including ice cores, tree rings, borehole temperatures, glacier length records, and historical documents. Evidence for regional warmth during medieval times can be found in a diverse but more limited set of records including ice cores, tree rings, marine sediments, and historical sources from Europe and Asia, but the exact timing and duration of warm periods may have varied from region to region, and the magnitude and geographic extent of the warmth are uncertain.

• It can be said with a high level of confidence that global mean surface temperature was higher during the last few decades of the 20th century than during any comparable period during the preceding four centuries. This statement is justified by the consistency of the evidence based on a wide variety of geographically diverse proxies.

• Less confidence can be placed in large-scale surface temperature reconstructions for the period from A.D. 900 to 1600. Presently available proxy evidence indicates that temperatures at many, but not all, individual locations were higher during the past 25 years than during any period of comparable length since A.D. 900. The uncertainties associated with reconstructing hemispheric mean or global mean temperatures from these data increase substantially backward in time through this period and are not yet fully quantified.

• Very little confidence can be assigned to statements concerning the hemispheric mean or global mean surface temperature prior to about A.D. 900 because of sparse data coverage and because the uncertainties associated with proxy data and the methods used to analyze and combine them are larger than during more recent time periods.

In short:

--The reconstructions for A.D. 900 to 1600 are less certain. The reconstructions before A.D. 900 are not certain at all.

--The Little Ice Age was from 1500 to 1850.

--We are warmer now than we have been for 400 years.

In other words, we are now warmer than at any time since the middle of the Little Ice Age. Is this all that surprising?

If you look at the curves for tree rings and Moberg's multiproxy, we're about at the same temperature as during the Medieval warm spell in about 1000 AD.