Posted on 11/09/2006 6:04:22 AM PST by chessplayer
The pdf file linked in the original article contains a black and white version from a UN 1996 report on climate change, and there is a set of graphs from a 2005 senate report on page 12...
I must assume the lower graph was created by the author to illustrate the inaccuracy of the "hockey stick" graph..
Simple variations in scale on graphs can make them look different, but the author's example is at least consistent with historical record..
The "hockey stick" is not..
Unknown. The Second Assessment Report is not online. Only the Summary for Policy Makers is online, and this is what it says about the millenial temperature history:
"The limited available evidence from proxy climate indicators suggests that the 20th century global mean temperature is at least as warm as any other century since at least 1400 A.D. Data prior to 1400 are too sparse to allow the reliable estimation of global mean temperature."
So; that whole big orange high temperature curve before 1400 that dominates the lower graph? Unreliable (according to the state of the science in 1996).
On FURTHER review, the same graph also appeared in the first IPCC report -- i.e., it was re-used in the second report (**see below). There was something of a discussion of it on ClimateAudit here:
This tidbit indicates that the graphs, including the bottom one, are simply schematic diagrams. I find it hard to believe that these graphs were not based on any published research (considering that's how the IPCC does what it does), so if anyone wants a real detective case, find it what those graphs are based on. Until then, they are just cartoons, including the version printed in Monckton's article!
But I haven't given up:
This is what is stated about the figure from which the bottom graph in the figure from Monckton's article is derived:
"A schematic (non-quantitative) curve was used to represent temperature variations over the last 1000 years in chapter 7. The vertical temperature scale was labelled as "Temperature change (°C)" but no numerical labels were given; it could be taken to imply that temperature variations of the MWP and LIA were each of the order of 0.5 °C from the temperature around 1900. The section specifically states recent climate changes were in a range of probably less than 2 °C. The 1990 report noted that it was not clear whether all the fluctuations indicated were truly global (p 202). The graph had no clear source, and disappeared from the 1992 supplementary report."
** Note: since I composed this on the fly, apparently I was wrong above, and the figure does not appear in the 1996 report (as Monckton claims).
So how much has Monckton got wrong? One, based on all my research, it strongly appears that the graph doesn't appear in the 1996 report (the Second Assessment Report), it only appears in the first (1991) report. Second, assignment of actual temperatures to the graph is erroneous. Third, the statement of the IPCC report itself is that temperatures before 1400 cannot be reliably estimated; this is echoed by the National Academy of Sciences report addressing the Mann et al. "hockey stick", which stated that there is currently insufficient data prior to 1600 to make any quantitative comparisons to modern temperatures. (Even though they did use the weaselly-worded phrase saying that it is "plausible" that current temperatures are the highest in the last millenium.)
What is more relevant (and accurate) is the figure appearing on page 12 of Monckton's supporting document:
warm-refs.pdf (I can't extract the figure for display here; it shows multiple reconstructions, which Monckton fails to note that some are regional, but they all show that the MWP was not significantly warmer than now, IF that data can be reasonably relied upon.)
So the bottom graph is very misleading; if pressed, I'd have to say it was intended to deceive.
Maybe. There is clearly a difficulty that the MWP and the LIA appeared to be regionally intensified in Europe, probably due to ocean circulation variability. Because this area is sensitive to variations in ocean circulation, the "intensification" of effects points to ocean circulation as a player. The other player, especially for the LIA, is reduced solar output during the Maunder Minimum (the most famous) and two other shorter sunspot number minima.
Cuckoo science (addresses parts of Monckton)
Surface Temperature Reconstructions for the Past 2000 Years
Opening paragraph: "There is sufficient evidence from tree rings, boreholes, retreating glaciers, and other "proxies" of past surface temperatures to say with a high level of confidence that the last few decades of the 20th century were warmer than any comparable period in the last 400 years, according to a new report from the National Research Council. Less confidence can be placed in proxy-based reconstructions of surface temperatures for A.D. 900 to 1600, said the committee that wrote the report, although the available proxy evidence does indicate that many locations were warmer during the past 25 years than during any other 25-year period since 900. Very little confidence can be placed in statements about average global surface temperatures prior to A.D. 900 because the proxy data for that time frame are sparse, the committee added."
Relevant excerpt: "The Research Council committee found the Mann team's conclusion that warming in the last few decades of the 20th century was unprecedented over the last thousand years to be plausible, but it had less confidence that the warming was unprecedented prior to 1600; fewer proxies -- in fewer locations -- provide temperatures for periods before then. Because of larger uncertainties in temperature reconstructions for decades and individual years, and because not all proxies record temperatures for such short timescales, even less confidence can be placed in the Mann team's conclusions about the 1990s, and 1998 in particular. ... The committee noted that scientists' reconstructions of Northern Hemisphere surface temperatures for the past thousand years are generally consistent. The reconstructions show relatively warm conditions centered around the year 1000, and a relatively cold period, or "Little Ice Age," from roughly 1500 to 1850. The exact timing of warm episodes in the medieval period may have varied by region, and the magnitude and geographical extent of the warmth is uncertain, the committee said. None of the reconstructions indicates that temperatures were warmer during medieval times than during the past few decades, the committee added."
Very important article.
I would point out one thing not mentioned so far..
If there is truly no evidence that it has been hotter than it is presently, then there is a distinct possibility of our being at or near the peak of a warming cycle...
That may indicate the beginning of a new cooling cycle...
One that may last several hundred years, or several thousand...
It may not be as severe as the Little Ice Age, but then again, it could be very severe..
And that change could take place in as little as 70 years..
bump to find you for later reply
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