Climate models have performed quite well..

The "hockey stick" describes a reconstruction of past temperature over the past 1000 to 2000 years using tree-rings, ice cores, coral and other records that act as proxies for temperature (Mann 1999). The reconstruction found that global temperature gradually cooled over the last 1000 years with a sharp upturn in the 20th Century. The principal result from the hockey stick is that global temperatures over the last few decades are the warmest in the last 1000 years.


Figure 1: Northern Hemisphere temperature changes estimated from various proxy records shown in blue (Mann 1999). Instrumental data shown in red. Note the large uncertainty (grey area) as you go further back in time.

A critique of the hockey stick was published in 2004 (McIntyre 2004), claiming the hockey stick shape was the inevitable result of the statistical method used (principal components analysis). They also claimed temperatures over the 15th Century were derived from one bristlecone pine proxy record. They concluded that the hockey stick shape was not statistically significant.

An independent assessment of Mann's hockey stick was conducted by the National Center for Atmospheric Research (Wahl 2007). They reconstructed temperatures employing a variety of statistical techniques (with and without principal components analysis). Their results found slightly different temperatures in the early 15th Century. However, they confirmed the principal results of the original hockey stick - that the warming trend and temperatures over the last few decades are unprecedented over at least the last 600 years.




Hockey_Stick_glacier.gif
 
futurecurrents said:
No fraudulent manipulation. Hockey stick is correct. All you have is bullshit sources of fraud and deception. Your sources are lies.
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The IPCC's Second Assessment Report was a fraud and deception. Good to know. That's where the chart is from. I guess this means that everything from the IPCC is a fraud and deception - of course this means the IPCC is a bullshit source.
 
gwb-trading said:
The IPCC's Second Assessment Report was a fraud and deception. Good to know. That's where the chart is from. I guess this means that everything from the IPCC is a fraud and deception - of course this means the IPCC is a bullshit source.
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Yes, up is down and you are not an idiot.
 
Yes, the hockey stick is real and factual. Proven by the world's top climate scientists via multiple proxies and statistical analysis. It was even proven by a former skeptic. Gore was/is right.

The propaganda from jem's right wing websites is fraud because it is wrong and is backed by powerful money interests. Sorta like the tobacco thing.
 
http://junksciencearchive.com/Hide_the_decline.html

Origins of the hockey stick

In 1990, the IPCC published its First Assessment Report (FAR) containing this representation of Earth’s recent climate history:

FAR page 202, graphic 7c (IPCC, 1990)

FAR page 202, graphic 7c (IPCC, 1990)

This graph did not well suit those crusading against manmade emissions of greenhouse gases as they wished to claim the current apparent warmth was “unprecedented,” and therefore, by circumstantial inference, driven by human action.

In 1995, University of Oklahoma geoscientist David Deming reconstructed North America’s historical temperatures from borehole data.[1] One of the more important players, (widely believed to be Jonathan Overpeck [2] and which has never been denied [3]), subsequently sent Deming an email that said,

“We have to get rid of the Medieval Warm Period.”

The Medieval Warm Period is believed to have been warmer than current temperatures. Obviously, this apparent warmth was not caused by manmade emissions of greenhouse gases.

Despite the expressed concerns of those desirous of attributing current warmth to human activities and the problem posed by the Medieval Warm Period, the IPCC maintained the warming in its Second Assessment Report as follows:

Climatic changes in Europe

But by the IPCC’s Third Assessment Report (TAR) in 2001, things had changed somewhat.
 
Yes, the hockey stick is real and factual. Proven by the world's top climate scientists via multiple proxies and statistical analysis. It was even proven by a former skeptic. Gore was/is right.

The propaganda from jem's right wing websites is fraud because it is wrong and is backed by powerful money interests. Sorta like the tobacco thing.
 
NH_Temp_Reconstruction.gif



Historical records of glacier length can be used as a proxy for temperature. As the number of monitored glaciers diminishes in the past, the uncertainty grows accordingly. Nevertheless, temperatures in recent decades exceed the uncertainty range over the past 400 years (Oerlemans 2005).



Of course, these examples only go back around 500 years - this doesn't even cover the Medieval Warm Period. When you combine all the various proxies, including ice cores, coral, lake sediments, glaciers, boreholes & stalagmites, it's possible to reconstruct Northern Hemisphere temperatures without tree-ring proxies going back 1,300 years (Mann 2008). The result is that temperatures in recent decades exceed the maximum proxy estimate (including uncertainty range) for the past 1,300 years. When you include tree-ring data, the same result holds for the past 1,700 years.
 
Paleoclimatology draws upon a range of proxies and methodologies to calculate past temperatures. This allows independent confirmation of the basic hockey stick result: that the past few decades are the hottest in the past 1,300 years
 
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