Why was the medieval warm period not reflected in the Hockey stick graph?

Question

Surely a blunder as obvious as this could not have been made by objective science.

The medieval warm period is well established history.

For farming to have occurred on Greenland as is documented wouldn't it have to have been warmer than the present. There isn't much farming there today after all.

Is the hockey stick graph reliable?

It appears thousands of reputable scientists have stake their reputation on it.

Answer 1

How can one claim that 20th century warming is unnatural, when in the past we had natural warmings?  That is why the doom sayers wanted it eliminated.

“ Around 1996, I became aware of how corrupt and ideologically driven current climate research can be. A major researcher working in the area of climate change confided in me that the factual record needed to be altered so that people would become alarmed over global warming. He said, "We have to get rid of the Medieval Warm Period."

Dr. David Deming (University of Oklahoma)

GCNP I suggest you read other sources of info, other than the IPCC.  Too bad they ignore other studies that would question their hypothesis.  The GRIP (Greenland) borehole temperature record is not a proxy, but a direct measure of temperature (Dahl-Jensen et al. 1998). It shows that current warmth is not unusual in the context of the last 2,000 years. A similar result for the last 1,000 years has also been obtained from borehole temperatures in the Ural Mountains (Demezhko and Shchapov, 2001).

Not only was farming

Answer 2

In 2006, researchers at the University of Toronto exposed the "hockey stick" graph as a fraud.  Using the same software that was used to produce this graph, they input several different sets of random temperature data and the resulting graph was the same each time.

Answer 3

Wiki is a *vast* left wing propaganda machine,

which is to say, lots of people seem to be contributing to it;

which seems to say, that most people are "left-wing" by

your judgement.

Answer 4

Its tough to answer when you don't say what hockey stick graph you are talking about.  I've got graphs of the composition of the atmosphere that look like hockey sticks and go back 10,000 years.

Answer 5

In my opinion, it has been thoroughly discredited.  I always like the fact that they begin their graphs in 1890 or thereabouts after  a very cold period to maximize the warming.  Warming used to be a nice word and now it has been demonized to a ridiculous extent.

If you look at the graph of temperatures over a hundred thousand years or more, it becomes apparent that we are near the likely top of the steep rise coming out of the last period of glaciation.  There is some evidence that it has been a more stable time than most transitions out of the ice age.  Still, it comes as no shock to me that the 20 th Century might be the warmest of the millineum.  That doesn't lead me conclude that man must be the cause.  

After testing the work of Mann et al. (1998), McKitrick commented

    "The Mann multiproxy data, when correctly handled, shows the 20th century climate to be unexceptional compared to earlier centuries. This result is fully in line with the borehole evidence. (As an aside, it also turns out to be in line with other studies that are sometimes trotted out in support of the hockey stick, but which, on close inspection, actually imply a MWP as well.)"

Answer 6

It was regional, not global in scope, so your claim of "well established history" is irrelevant to the Hockey stick graph (which was dealing with global temperatures).

And you must be misinformed when you write "thousands of reputable scientists have stake their reputation on it".  There are numerous temperature reconstructions and multiple threads of evidence for global warming.  So not a single scientist (let alone thousands) is staking their reputations on this one graph. That would be silly.

Edit:

Birdog - This graph is most definitely NOT the holy grail.  The acceptance of global warming wouldn't be any different if Mann had never done his study (it's but one pea in a mountain of pods). There are enough other studies (and other lines of evidence) to make the argument for global warming overwhelming. You are simply trying to set-up a straw man argument and several of us have collapsed your straw foundation.

Answer 7

http://ipcc-wg1.ucar.edu/wg1/Report/AR4W...

Page 467, Figure 6.10

Page 468, Box 6.4

If you're not going to even try to understand the best available science, instead substituting what you want to believe to be true, then you will be forever doomed to irrelevancy when adults come together to talk.

HI Eric!  Hey, I looked for Dahl-Jensen et al. (1998) but can't find anything except a seismic study which makes no reference to borehole temperatures.  Are you sure that reference is correct?  The Demezkho paper is interesting, but  they extract temperatures using an inversion technique that involves a lot of assumptions and could be wildly inaccurate.  That it predicts temperature amplitudes that are much larger than found by other studies for earlier times (e.g., the holocene maximum) makes me suspect it is getting the amplitude for the MWP too large as well (aside from the fact that their reconstructed temperature for the MWP is within the error range in the IPCC report (which lists a number of independent reconstructions, all of which were peer-reviewed).  So, it would appear to me that you are cherry-picking results that you want to believe, rather than objectively assessing all available data.  Also, you do understand the difference between these point measurements you are citing, and the multiproxy hemispheric reconstructions discussed by in the IPCC report right?

Ah, there it is, it's DahlJensen, no hyphen, in SciCitation index make a note of that will you?  There's a luv.

Answer 8

oh not this old thing again. the mwp was northern hemisphere local event

http://en.wikipedia.org/wiki/Hockey_stic...

http://www.realclimate.org/index.php/arc...

http://www.sciam.com/article.cfm?id=behi...

http://www.aip.org/history/climate/20ctr...

bored now. off for my tea.

ha ha you are just annoyed because a project like wiki with no   centralised control can be so phenomenally sucessful. by all means check out the excellent and exhaustive references and links provided in this wiki article.

Answer 9

The reason is, the hockey stick graphs span large areas of time, and the warm period was only a few degrees warmer, and not for a large enough amount of time to show up tremendously. An extremely detailed one will contain it, but most do not go into excessive detail.

Pointing out what I said earlier, it does not require excessive warming for small things like farming to take place in Greenland. Take nowadays, it has heated by less than 2 degrees in a few decades, and half the north pole has melted or is melting!

Answer 10

The original data for the hockey stick didn't fit their preconceived notions, so the relevant data was deleted.

The Vikings were able to colonize Newfoundland and Nova Scotia because the MWP melted the ice blocking the Northwest Passage. But AGW people won't admit that to save their lives.

Answer 11

Any temperature measurements over 50 years old are subject to scrutiny since the measurements were never taken with instruments as accurate as we now have, nor were there remote sensors capable of measurements even close to what we've had in the last twenty years.

Any measurement of any temperature within a 1 to 2 degree temperature range that someone claims is over 100 years old should be taken with a grain of salt as this whole AGW thing should be.