AG, you need to put on your reading glasses and take another look. I tracked down the source of your graph by viewing the page source, and this is NOT a global temperature record; this is from the GISP2 core in Greenland. It's high Arctic, and furthermore, it's in an area that is profoundly influenced by the state of the thermohaline circulation and deep water formation in the adjacent waters. In short, this is a region known to have much higher excursions up/down with regard to temperature than the globe. Compare your graph to the one found here:
The Millenial Temperature Record"
and you'll see that global temperature excursions are considerably moderated. Now, a variation of this particular record was published by Mann et al. and figures prominently in the IPCC 2001 TAR. It was questioned a bit by the more recent results of Esper et al. But, in the grand tradition of peer-review, it turns out that both analyses are valid (but different) and the story told by both is essentially the same. We can go into this in further detail if you want; I've been over this ground before.
This Patrick Michaels ?
The same.
I woulde say you have alot of very big "If"s and "could be"s to get over before a "will be" has much meaning as regards any contribution that mankind may have on the climate or effects thereof.
I try to write like a realist, not an alarmist.
. Now, a variation of this particular record was published by Mann et al. and figures prominently in the IPCC 2001 TAR. It was questioned a bit by the more recent results of Esper et al. But, in the grand tradition of peer-review, it turns out that both analyses are valid (but different) and the story told by both is essentially the same.
Of Course Esper et al was interesting in that it confirmed the presense of the Little Ice Age as a global phenomena from which any change in current global temperatures must be reconned, Seeing as one of the problems with the IPCC version of events wants to ignore the return of global temperatures to a more moderate level from the Little Ice Age temperatures, as well as ignoring the periods in the current inter-glacial even warmer periods than now that by no means can be accounted for by any anthropogenic inputs:
http://www.co2science.org/journal/2001/v4n15c2.htm
Two separate chronologies were thus developed: one from trees that exhibited age trends that are weakly linear and one from trees with age trends that are more nonlinear. The results, in their words, were "two nearly independent tree-ring chronologies covering the years 800-1990," which were "very similar over the past ~1200 years." These tree-ring histories were then calibrated against Northern Hemispheric (0 to 90°N) mean annual instrumental temperatures from the period 1856-1980 to make them compatible with the temperature reconstructions of Mann et al.
What do the results show? The biggest difference between the Esper et al. and Mann et al. temperature histories is the degree to which the coolness of the Little Ice Age is expressed. The Little Ice Age is much more evident in the record of Esper et al., and its significantly lower temperatures are what make the Medieval Warm Period stand out more dramatically in their temperature reconstruction. Also, they note that "the warmest period covers the interval 950-1045, with the peak occurring around 990." This finding, they say, "suggests that past comparisons of the Medieval Warm Period with the 20th-century warming back to the year 1000 have not included all of the Medieval Warm Period and, perhaps, not even its warmest interval."
In commenting on these findings in a companion "perspective" paper, Briffa and Osborn (2002) make several interesting and important points. First, they acknowledge that "the last millennium was much cooler than previously interpreted" and that "an early period of warmth in the late 10th and early 11th centuries is more pronounced than in previous large-scale reconstructions." In fact, the Esper et al. record makes it abundantly clear that the peak warmth of the Medieval Warm Period was fully equivalent to the warmth of the present.
Only problem is that both Mann et al and Esper et al, are constrained to specific land areas from which tree ring data for each series were were generated. Thus neither is a "global" a representation as should be had to base policy decisions on or as it were to calibrate or check computer "global" climate models against. Seems temperature measurements are severely lacking in a global sense even in looking at the Mann et al data that IPCC uses.
http://www.co2science.org/edit/v5_edit/v5n13edit.htm
When considering the subject of global warming, and especially when considering ways to change the way the world does business (emits CO2 to the atmosphere) based on purported changes in global temperature, it is only prudent to have a good global record of temperature over as long a time period as possible. Currently, we are not in great shape in this regard; for the temperature history most commonly employed in these deliberations (Mann et al., 1999) pertains to only a portion of the land area of the globe, which is but a portion (and a minor one at that) of the entire "water-world" we call earth. Hence, it is absolutely essential that we obtain more long-term sea surface temperature (SST) data, which is what the study of Linsley et al. does. A second important reason for obtaining such data is that the information could greatly increase our knowledge of the ability of coral reefs to withstand the thermal stresses they are predicted to encounter in the face of the CO2-induced warming of the globe that the IPCC claims is already upon us.