Message Font: Serif | Sans-Serif
No. of Recommendations: 6
Sorry, DB2, but you're not exactly acting as a fair broker of facts here.

Mann's "Hockey Stick" has been subjected to a great deal of scrutiny ever since it was published in 1998/1999. McIntyre and McKitrick (2003) has been hailed by the Wazzup gang as some sort of definitive refutation of Mann's work. Nothing could be further from the truth.

Mann's 1998/1999 (MBH) papers have been reviewed by many (including several overtly hostile reviewers). When all is said and done, his work remains relatively intact.

As for McIntyre and McKitrick (MM03), their work hasn't fared all that well.

The Huang, Pollack & Shen 2000 borehole temperature reconstruction covering the past five centuries supported the conclusion that 20th century warming was exceptional.

In a study published in November 2004, Edward R. Cook, Jan Esper and Rosanne D'Arrigo concluded that "annual temperatures up to AD 2000 over extra-tropical NH land areas have probably exceeded by about 0.3 °C the warmest previous interval over the past 1162 years".

A study by Anders Moberg et al (2005) used a wavelet transform technique to reconstruct Northern Hemisphere temperatures over the last 2,000 years, combining low-resolution proxy data such as lake and ocean sediments for century-scale or longer changes, with tree ring proxies only used for annual to decadal resolution. They found there had been a peak of temperatures around AD 1000 to 1100 similar to those reached in the years before 1990, and supported the basic conclusion of MBH99 by stating "We find no evidence for any earlier periods in the last two millennia with warmer conditions than the post-1990 period."

In 2007 the IPCC AR4 noted the MM03 claim that MBH98 could not be replicated, and reported that "Wahl and Ammann (2007) showed that this was a consequence of differences in the way McIntyre and McKitrick had implemented the method of Mann et al. (MBH98) and that the original reconstruction could be closely duplicated using the original proxy data.

In their renewed criticism of MBH98, McIntyre and McKitrick's 2005 paper (MMO5) reported a technical statistical error.In the article, the authors wrote that the "Hockey Stick" shape was the result of an invalid principal component method, and that "the MBH98 method effectively selects only one species (bristlecone pine)" to produce the hockey-stick shape.

Others found the issues raised by McIntyre and McKitrick were minor and did not affect the main conclusions of MBH. Technical issues were discussed in RealClimate on 18 February in a blog entry by Gavin Schmidt and Caspar Ammann, and in a BBC News interview Schmidt said that by using a different convention but not altering subsequent steps in the analysis accordingly, McIntyre and McKitrick had removed significant data which would have given the same result as the MBH papers.

Shall we then contend that McIntyre (a businessman) abused and mistreated data for some nefarious purpose?

In February 2006, two more reconstructions were published, using different methodologies, and supported the main conclusions of MBH. Rosanne D'Arrigo, Rob Wilson and Gordon Jacoby suggested that medieval temperatures had been almost 0.7°C COOLER than the late 20th century but less homogenous. Osborn and Briffa found the spatial extent of recent warmth more significant than that during the medieval warm period. They were followed in April by a third reconstruction led by Gabriele C. Hegerl.

The National Research Council stated that "The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators".

Despite all the above, the Wazzup Circus continues to flog Mann and extol McIntyre. That's what propagandists/obfuscationists do. Meanwhile, Science marches on:

This report presents a study of the variability in a recently published April to September gridded reconstruction temperatures in Europe and an analysis of their extremes. This reconstruction was based on tree rings, historical documents, pollen assemblages and ice cores. The methodology used, an original spectral analog method, preserves long-term variations and the variability of temperature series, which guarantees the pertinence of the analysis of the extremes over a period as long as the last millennium. The analysis of the extremes was performed with the peak-over-threshold (POT) method over two warm periods (A.D. 1000–1350 and 1880–2007) and a cold period (A.D. 1350–1950).

We found that (1) according to the long-term variations shown in this reconstruction, the growing season temperature during the last decade has exceeded all of those observed during the Medieval period...

Meanwhile, researchers continue examine proxy data:

So-Called Medieval Warm Period Not So Warm After All

The so-called Medieval Warm Period (MWP), a 400-year span from about 950 to 1220 A.D. when the Vikings colonized Greenland, was relatively balmy by the standards of the past 2,000 years, leading some to argue that the global warming we’re now experiencing isn’t that big a deal. But a new report in the journal Geology argues that the MWP wasn’t all that warm after all — and certainly not as warm as the climate is today.

According to William D’Andrea of Columbia University’s Lamont-Doherty Earth Observatory and his co-authors, summer temperatures in the Svalbard Archipelago, a group of islands in the Arctic Ocean about 400 miles north of Norway, have been between 3.6°F and 4.5°F HIGHER over the past 25 years, on average, than the summers the Vikings enjoyed.

Please refer to the "Hockey Stick Controversy" Wiki entry for detailed information and a complete list of references. I merely summarized a few pertinent points.
Print the post  


What was Your Dumbest Investment?
Share it with us -- and learn from others' stories of flubs.
When Life Gives You Lemons
We all have had hardships and made poor decisions. The important thing is how we respond and grow. Read the story of a Fool who started from nothing, and looks to gain everything.
Community Home
Speak Your Mind, Start Your Blog, Rate Your Stocks

Community Team Fools - who are those TMF's?
Contact Us
Contact Customer Service and other Fool departments here.
Work for Fools?
Winner of the Washingtonian great places to work, and Glassdoor #1 Company to Work For 2015! Have access to all of TMF's online and email products for FREE, and be paid for your contributions to TMF! Click the link and start your Fool career.