An Investigation into The Hockey Stick Graph

Michaek Mann's Hockey Stick Temperature Graph

Fig 1.  Last 1000 years temperature estimation made by Michael Mann.

Fig 1. This graph is taken from the UNEP/GRID-Arendal site

This graph is the Hockey Stick Graph created by geophysicist Michael Mann. It is also called MBH98 after the three author Mann, Bradley, Hughes and from the year it was compiled 1998.

As you can see the temperature graph shows that the temperature just varied a few tenth of a degree before 1900. This graph was publish in the very prominent scientific magazine Nature and made quite a sensation. It was also prominent display in several places in the 2001 IPCC report, the UN Intergovernmental Panel on Climate Change.
It has now been removed from the latest 2007 IPCC report for policymakers because it has become to much of an embarrassment for the IPCC to include it.

The graph was subsequently criticized by many global warming skeptics and historians, because weather events such as the Medieval Warm Period and the Little Ice Age were absent. Although with little imagination one can see that the temperature is a little higher in Medieval time period and little cooler after 1500. But the variation is far to small to correspond to historical records.

Criticism from some skeptics have been centered around the statistical Auto Regression method which was used and the associated computer program. It was suspected that it might be responsible for data set end irregularities which could be responsible for some of the rapid rise in the 20th century.

I don't know about that, it is hard for me to judge, but I believe the statistical method he used to display the graph is correct and based on the collected data.

The flaw is in the method in collecting the various types of sampled data or proxy as it is called in climatology circles. It turns out that the data is collected from different sources such as corals, tree rings, ice cores and temperature records.

The temperature is only taken from measurements during the last century. The temperature estimation is mainly taken from biological materials and is primarily from tree rings. With tree ring analysis or Dendrochronology which is its scientific name, it is possible to evaluate the growing condition of trees. The distance between the rings are larger if the growing season is longer for a specific year and it becomes shorter if the growing season is short. However the tree ring growth is also affected by other conditions such as humidity, the amount of sunshine, soil and by fertilization.

Because not enough reliable temperature recordings exist before the 1900, the temperature estimations before that time are largely based on tree ring recordings. In order to estimate the tree ring growth correspondence to temperature variations a normalization was made from tree ring recordings during the 20th century by matching them against made temperature recordings. The problem of the tree ring recordings after 1900 are that they do not follow the temperature changes correctly.

The condition for tree ring growth after 1900 have changed substantially.

What was missed and what cause the flaw is something that every school kid learn at school or at least they use to!

And that is the biological mechanism of Photosynthesis!

The tree rings are affected by increased levels of CO2. In other words the tree rings grow larger today than they did 100 years ago. A major part of the extra tree ring growth is from elevated levels of Carbon Dioxide instead from the expected temperature increase. Another problem is from the so called Urban Heat effect. This effect is caused at temperature recording stations in or near urban areas which  becomes hotter over time because of urban sprawls. The concrete and asphalt heats up the area. A temperature station which 100 years ago was out in the countryside may now be in an urban area. We know that most of the recorded warming have been in the northern hemisphere in the US, Europe, Russia and in the Artic. Some of that recorded warming may be caused by The Urban Heat Effect.

The made normalization and matching from the temperature and tree ring growth means that the temperature signals before 1900 has been severely dampened leaving the erroneous impression that temperatures before 1900 were very static. If you look closely at the hockey stick graph a marked kink can be seen where the temperature recordings are absent and where the temperature recordings are included. This is visible around year 1900 and is a result from the different normalization of the tree rings.

If you look at the temperature recording going back to 1850 at the bottom of the home page you will see that the temperature variations are of the same magnitude before 1900 as the are after the 1900.


You don't believe that the CO2 increase has had an affect on tree and plant growth?

Then look at this..!!

The carbon dioxide fertilization effect.

Is Michael Mann aware of this flaw in the graph?

Of course he is. Yet he is still defending the hockey stick graph, despite the problem with data contamination from CO2 fertilization of tree rings.

Bristlecone Pine Trees, are good proxies for measuring the combined amount of humidity, sunlight and atmospheric CO2.

BBC, one of the bastions of biased global warming propaganda broadcasted in September 2008 a series of program made by geologist and global warming alarmist Iain Stewart. In this clip he shows from where Michael Mann took most of the samples he used to build the hockey stick graph.

Bristlecone Pine Trees grow in the dry boarder regions of California and Utah at high elevations. The major advantages of using this tree in the temperature reconstruction is that it is possible to go back 2000 year using living trees and they are easily accessible. You don't need to dive down into a bog to get old tree logs. Another advantage if you want to erase historical climate variations and create a "global warming smoking gun", as in this case, is that temperature reconstruction from these trees are almost useless.

This is because the trees live in a dry region, they are very susceptible to CO2 fertilization and the CO2 drought resistance effect. Temperature only play a minor role and at high temperatures it is also susceptible to drought which reduces growth. Therefore the temperature growth relation can in fact can be reversed. The trees respond positive to higher CO2 levels, humidity levels and sunshine but not to temperature. In other words, temperature reconstruction which in large part is based on this tree is perfect if you want to erase The Medieval Warm Period and The Little Ice Age.


History From The Little Ice Age Is Still Visible In Scandinavia!

Few outside of the Nordic Countries may know this, but almost exactly 350 years ago, because of The Little Ice Age, Sweden conquered one third of what was then the Danish heartland.
Today, this is the southern and south western part of Sweden.

In 1655 a well equipped and trained Swedish Army invaded and occupied most parts of Poland. Although the invasion went according to plan, they didn't have a working plan for how to pacify and role over a hostile Polish population.
As a result the invaders met increasing resistance and soon found themselves fighting a guerilla war uprising.

Rumors of the quagmire the Swedish Army had run into spread around Europe. This tempted Sweden's arch enemy at that time, Denmark to declare war against Sweden on the 1st of June 1657.

The Swedish Army, in response, then quickly abandon Poland without losing to much face.

But instead of going home, sail over the Baltic Sea to defend their home country, the Army marched up through Germany and invaded the Jutland peninsula, the western most part Denmark. Which they quickly overran and occupied.

In order to end the war, their plan were then to invade Zealand and conquer Copenhagen the Danish capital. But at that time they had a big problem, this was because they lacked a nearby fleet which could help them with the transportation over to Zealand during an invasion attempt.

However they got unexpected help by the weather, because during the severe winter of 1657-1658 they didn't have to make that transportation by boat, but instead they could do it by marching over frozen waters. And so they did!

Crossing of the Great Belt by the Swedish Army in 1658

Crossing of the Great Belt by the Swedish Army in 1658

Propaganda painting from 17th century of when a Swedish Army crossed the frozen Baltic Sea in its Danish campaign during the Northern Wars. This crossing was only made possible by the cold weather during The Maunder Minimum.

So. the reason for this conquest was as a result of a march the Swedish Army made across The Frozen Belt Straits, the main waterways between the Danish islands and which was completed by The March Across the Great Belt made between February 5th and 6th in 1658. This extensive march over the frozen water was only made possible by the cold weather during The Maunder Minimum of The Little Ice Age.

10 days later they reached the outskirts of Copenhagen.

The Danes had expected a Swedish invasion attempt first later in the spring and felt protected by their strong navy. The sudden appearance of a large Swedish army outside the gates of the capital took them completely of guard. Instead of fighting, the Danes panicked, asked for peace and Denmark lost its eastern part in the following peace deal.

This March was made by an army of more than 10 000 soldiers comprising of infantry, cavalry and artillery that marched a distance of about half that between Dover and Calais or about 12 kilometers over frozen sea water of ice expanses.

Of course, today if you look at this sea strait in winter you will rarely ever see any ice floating in that wOf course, today if you look at this sea strait in winter you will rarely ever see any ice floating in that water.