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Climategate debunked? Mann and Briffa explaining the “Mick’s Nature Trick”

Published 01st December 2009 - 20 comments - 5384 views -

If you use only tree-rings, the "present global warming" is only 0.1°C warmer than Medieval Warm Period. Because above certain level of temperatures the tree-rings do not respond any more. But such slight warming was not enough to raise "global warming hysteria". So they improved it by adding the black line (instrumental records from our thermometers)... If we had MWP instrumental records, the medieval temperatures would also be much higher in the graph.


Was it warmer in Middle Ages than today? Or is our warming alarming? Is IPCC hiding the existence of MWP from us? Let us hear, how Mann et al. explain the famous "hide the decline" line from the leaked CRU e-mails (the Climategate affair from autumn 2009):



An excerpt from one November 1999 email authored by the head of the CRU, Phil Jones, reads, "I've just completed Mike's Nature [the science journal] trick of adding in the real temps to each series for the last 20 years (ie, from 1981 onwards) and from 1961 for Keith's to hide the decline."

Mick refers to Michael Mann, the author of Hockeystick graph.

RealClimate: "The paper in question is the Mann, Bradley and Hughes (1998) Nature paper on the original multiproxy temperature reconstruction....Note that the ‘hide the decline’ comment was made in 1999 – 10 years ago, and has no connection whatsoever to more recent instrumental records."



RealClimate: "As for the 'decline', it is well known that Keith Briffa's maximum latewood tree ring density proxy diverges from the temperature records after 1960 (this is more commonly known as the "divergence problem" - see e.g. the recent discussion in this paper) and has been discussed in the literature since Briffa et al in Nature in 1998 (Nature, 391, 678-682)."

  • Tree-rings react very weakly to increasing temperatures. It seems that upon reaching certain level of temperatures, the trees react weakly to any further temperature increase.
  • Tree-rings do not reflect the late 20th century warming.
  • Hence it is logical to assume, that they do not reflect the Medieval Warm Period either.
  • If you use only tree-rings you get this traph: no MWP but also no Global Warming in the late 20th century.

The divergence problem is well known and published. So it is odd, that someone still takes hockeystick seriously.



RealClimate: "The 'trick' is just to plot the instrumental records along with reconstruction so that the context of the recent warming is clear."

  • If you do not use this trick, tree-rings graph will show no warming in MWP but also no warming in the 20th century
  • But if you use this trick, you will get a hockey-stick: no warming in MWP, but big warming in the 20th century.... Miracle... Suddenly we can see tremendous gigantic unprecedented AGW. Alarm!



RealClimate: "Those authors have always recommended not using the post-1960 part of their reconstruction, and so while 'hiding' is probably a poor choice of words (since it is 'hidden' in plain sight), not using the data in the plot is completely appropriate, as is further research to understand why this happens."

  • Birffa used "Mick's Nature trick" (invented by Mann in 1998, when he invented the Hockeystick graph)
  • Briffa openly admitted, that thus acquired results are misleading and should not be used.
  • My conclusion is, that Hockeystick is also misleading and should not be used
  • Anything that uses Mick's Nature Trick is misleading and should be avoided



A) If you use tree-rings and no tricks, you get an almost flat line, with little curvature. No big "global warming".

B) If you use other than tree-ring data, you get the graph, which was in 1990 IPCC report (FAR): a big MWP (higher temperatures than now or same temperatures) and big LIA. This is why independent research confirms, thata MWP existed and was as warm as today, maybe warmer (see e.g. peer-reviewed literature at


Moberg, A., Sonechkin, D.M., Holmgren, K., Datsenko, N.M. and Karlen, W. 2005. Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data. Nature 433: 613-617.



Michael Mann and his bunch should be silent and stop their feeble excuses. The more they try to "explain" their frauds, the more they damage their reputation. Thanks to Mann's above confession it is clear now. Unprecedented Global Warming was really Mann-made.

Since our temperatures are not unique or alarming, there is no reason for climatic hysteria or hurried "mitigation measures". We have already experienced such temperatures in Middle Ages and we were just fine.




1) The CRU hack:Context (23 Nov 2009). RealClimate Website of Michael Mann et al. <> Michael Mann explaining in his own words.

2) A blog discussing the divergence problem in detail  clearly:

 3) CRU climate data already 95% available. CRU website (28 Nov 2009)  <> Here you can see a graph of what happens if you do/don't use Mick's Nature trick.

4) Craig Idso et al. MWP Project <> Listing of peer-review research documenting ther MWP period. This is real science, not IPCC.

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Vitezslav Kremlik on 01st December 2009:

Damn, by accident I published the article, before it was complete… The default status of our blog posts should be CLOSED, not OPEN. Damn. Apologies to readers.

Mike on 01st December 2009:

It’s the beginning of the end for all these alarmist crooks.

From Australia, the tides finally begin to turn

I would love to see a blog post in the same vein *wink wink*

We have won the battle, now we must win the war!

Vitezslav Kremlik on 01st December 2009:

Now the post is complete and ready.

Hemant Anant Jain on 01st December 2009:

Your post is too late.
Here’s your challenge:

Vitezslav Kremlik on 01st December 2009:

Hemant, I used to think you are more clever. Some of your comments used to quite smart. I misunderestimated you.

Comment on this blog posts of mine, if you have the “cojones”.

The fact, that the articles, that support “hockeystick” are not independent research (but Mann’s friends) is well documented in WEGMAN REPORT. Go read it.

Note: Skeptics do not deny, that we had global warming. We just say, in MWP it was warmer. Colder and warmer periods take turns. It is normal. No reason for hysteria. Or for finding a scapegoat.

Vitezslav Kremlik on 01st December 2009:

Where are you? Federico, Hemant? You have nothing to say? No “witty” comment? No arguments?

Of course, what could you say? You might just say “we had good intentions, but we were wrong, sorry”

Adela on 01st December 2009:

‘No reason for hysteria.’

I’m sorry Vitezslav, but of everything written here, the only hysterical notes are several comments written by Mike. 

Everybody else (including you) writes his/her opinions and arguments as they know better. Sometimes the posts are insightful, some other times they’re informational or very well researched. But no hysteria whatsoever.

Vitezslav Kremlik on 01st December 2009:

Adela, when I wrote about hysteria, I referred to statements of guys like Pachauri or Al Gore, who say, that unless we DO SOMETHING within 10 years (according to latest interview it is only 3 years), climate is doomed…

Such statements are alarmist and hysteric. And based on CRU discredited pseudo-science. Nothing more.

Adela on 01st December 2009:

Still, YOU calling their statements ‘hysteria’ proves the way YOU understand them. Which is quite interesting.

More than anything, as a reporter of science, you should be able to preserve your objectivity, regardless of how someone may sound in a speech.

But you don’t seem to, and you lose credibility.

Adela on 01st December 2009:

By the way, if you save a published post as closed, it will no longer be published until you save it as open again. smile

Mike on 02nd December 2009:

A victory for common sense smile

Sentate rejects ETS

Vitezslav Kremlik on 02nd December 2009:

Adela, most your comments so far seemed pretty objective and unbiased so far.

However I lack to understand, how Pachauri’s hysteric remarks, which are unfounded in science, make ME to lose credibility. I thought his remarks damage HIS credibility. Or not?

The evidence, that our warming is/was alarming and unprecedented, was based on CRU lies and “tricks”. Based on nothing. In fact our temperatures are pretty normal. No reason for alarm.

Vitezslav Kremlik on 02nd December 2009:

Sorry, to put this line here again, but… Why are all alarmists missing from the discussion below this article?

You used to have so many comments and now nothing? Run out of arguments?

Adela on 02nd December 2009:

What you interpret as hysteria, I may interpret as excitement. Others may interpret as insightful or stupid or inspirational and so on.

It’s not for you to decide for everybody whether it is hysteria or not, but it is for you to report objectively and let everybody else draw his/her own conclusions.

When you spice up objectivity with subjective remarks, you lose credibility, too. Because your personal beliefs affect your reports.

Obviously, this is valid for anyone who does it. And I think ‘being objective no matter what’ is the first law of journalists, too.

As for ‘In fact our temperatures are pretty normal.’
They are not. I am sorry but there’s no scientist (being him skeptic or supporter) that can change the weather outside and the cycle of seasons. Regardless of any human trick, nature itself proves that you are wrong with this statement.

Mike on 02nd December 2009:

I have a theory. This is a competition right? Prizes for most views, comments, etc? They would rather bait you to their own threads so they can collect on the loot! And it’s working!


Vitezslav Kremlik on 02nd December 2009:

Mick, you are wrong. The prizes are awarded arbitrarily. It has nothing to do with the number of comments, their quality or number of hits per page.

The most commented post is Tom Schaffer’s “Taking sides with the truth”, but so far he has not been awarded any prize in none of the three rounds of awards.

Unlike normal blogs, where you have your “rating” calculated by a computer accoridng to qty of visits plus “bonuses” awarded by visitors.

Vitezslav Kremlik on 02nd December 2009:

Adela, since 1970 the sea-surface temperatures have been rising at cca 0.1°C a decade.

If you say, that in 3 yeas we will be doomed because of this… I call it OVERREACTING!

On average, between 1950 and 1993, night-time daily minimum air temperatures over land increased by about 0.2°C per decade. This is about twice the rate of increase in daytime daily maximum air temperatures (0.1°C per decade).

Yes, these data of course are not quite reliable. Because they are from IPCC.

Adela on 02nd December 2009:

Exactly, but overreacting is different than hysteria. smile

The use of proper wording makes a huge difference in writing a blog post/report/article etc.

That’s what I wanted to emphasize in the first place.

Dave McK on 07th December 2009:

The word hysteria comes from a time when it was falsely believed that crazy mood swings were due to the uterus. That’s been repackaged and still has currency to this day.
Testeria would be more apropos, but alas, it requires a neologism…

Similarly, the notion of sin is constantly repackaged and given away for donations.

Modern global warmists have merely rebranded the ancient witchdoctor’s raindance and offer it to you in exchange for trillions of dollars and seriously fascist dogma supported by law (with them as the priesthood, of course)- not to mention the carbon derivative bubble that can mark up profits created from thin air.    best aggregation (with reference links)

Doug Marsh on 10th December 2009:

It is not relevant that there was a MWP and humankind survived. 

First, there were a LOT fewer people.  Nobody (except those affected) knew or cared if a couple of islands in the Pacific went under water.  If glaciers pulled back in the MWP, so what; just more land to farm.  But if the Himalayan glaciers vanish now, then a billion or more people are at serious risk.  The glaciers STORE the monsoon rain for year round use, and if that storage vanishes….  Maybe enough massive dams could fix that, but even that requires action and a massive amount of money.  But, the\n, why should any of us not getting water from those glacier care (its somebody else problem)?

Second, its the RATE OF CHANGE not the change that is important.  Did the MWP period happen in a few years or over many decades?  Humans and nature in general can adapt to slow changes; fast ones are a little harder to deal with, and as population continues to explode, it becomes harder and harder to adapt.

Regarding the whole tree-ring blow up, why would ANYONE use tree ring data if thermometer date is available?  Once sufficient thermometer data became available, it would be BAD science to use less reliable tree ring data.

Consider this:  What happens if those who say there isn’t global warming are right?  If we act to stop the CO2 increase, we have spent a lot of money, and we simply end up with clean energy sources that won’t run out and can’t be cut off by unfriendly governments.  On the other hand, if they are wrong and we don’t act?  Civilization and maybe a lot more is at serious risk.  I think this is a lot like playing Russian roulette with a twist.  I give you two six-guns.  One has 2 live shells (the “global warming is not a problem”; the other has 1 “global warming is serious and we need to act”, and you MUST play the game with one of them.  I know which one I’m going to use.

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