The global warming hockey stick is bad science

The global warming hockey stick is a graph of global temperature over time. It was produced by a scientist named Mann, who first published it in a scientific journal in the mid-nineties. He modified and included it in the 2000 report of the International Panel on Climate Change (IPCC). It is called a hockey stick because it shows very little variation of climate for the past thousand years until the 20th century, when temperatures soared. That makes the graph look like a hockey stick on its side, with the blade upward. The resolution claims that the curve is bogus. "Bad science" means that the curve does not correctly depict the climate of the past thousand years, and that the hockey stick was a result of errors in the methods in deriving the curve. This debate is not about whether global warming exists or whether human produced CO2 is causing significant global warming. The debate is not about whether Mann et al deliberately fudged the data. (I think he was honest, and that the errors were a product of the confirmation fallacy.) The debate is solely whether the hockey stick accurately reflects climate data. The IPCC report of 1990 had an entirely different graph of climate history. That graph showed a Medieval Warm Period (MWP), warmer than the present and lasting to about 1300, followed by the Little Ice Age, a period much colder than the present lasting through the early 1800's. Both disappeared in the hockey stick. The graphs are shown here: http://www.john-daly.com... -- scroll down to find the hockey stick. How did they disappear? Scientists, led by Ross McKitrick, a professor at the University of Guelph in Canada, spent enormous effort trying to reconstruct Mann's work to find out. Mann refused to supply his data or the computer program that he used to process the data. Under intense pressure, enough of the data was revealed and enough information about the algorithms was revealed to allow reconstructing and analyzing the methodology. The actual software has never been released. The details of the analysis are provided in full in a thirty page article by scientist Ross McKitrick, "The Mann et al Northern Hemisphere 'Hockey Stick': A Tale of Due Diligence." published in the book "Shattered Consensus" edited by Patrick Michaels. A good summary by a scientist who believes in human-caused global warming is from the MIT magazine Technology Review: http://technologyreview.com... The basic errors in the hockey stick derivation are: 1. Mann used an algorithm that normalized past data based upon the data of the last 78 years. This algorithm was tested by putting pure noise into the algorithm. Noise is fake data that just bounces around with no trends. When processed through the Mann algorithm, a hockey stick is produced. It makes hockey sticks out of nothing. 2. Mann used a method called "component analysis" as part of his method. When the raw climate data is put into a standard off-the-shelf computer program that does component analysis, the MWP and Little Ice Age reappear as they were in the 1990 IPCC report. 3. A variety of different types of data were used as inputs to Mann's analysis. The data are various proxies for temperature, like tree ring growth. Most of the data does not show a hockey stick, but one data set from the rings of trees growing at high altitudes did show a hockey stick. The literature says that high altitude tree data has unusual characteristics and should not be used as a temperature proxy. Mann not only included it, but weighted it 380 times more highly than other data. 4. There were errors in the method of filling in missing data. Mann's line of defense was that he didn't have the time to reveal his data or computer programs, and that no matter what critics did to reconstruct his work, they were not doing it right. Pressure mounted, and ultimately the National Science Foundation was asked to investigate the matter. They came back with an obfuscated report that seemed to confirm the criticisms, but at the same time didn't say the hockey stick was wrong. The matter was finally referred by Congress to a panel of statistical experts experienced in the processing of climate data. They determined unambiguously that the critics were correct, and that the hockey stick was invalid. The IPCC is primarily a political organization, so they felt no obligation to set the record straight. However, even politicians have to worry about saving face. The latest IPCC report covers a variety of analyses of past climate data, including the scientifically verifiable one. Separately, other studies and data has been produced relevant to the hockey stick. Paleoclimatologists have been building climate reconstructions at various points around the globe. These use tree rings, pollen in sediment layers, coral growth and other proxies for temperature. more than 350 such studies have been completed, and they prove beyond doubt that both the MWP and the Little Ice Age not only existed, but were worldwide. By 2003, the Harvard Smithsonian Center for Astrophysics concluded: "... the 20th century is neither the warmest century nor the century with the most extreme weather of the past 1000 years. The review also confirmed that the Medieval Warm Period of 800 to 1300 A.D. and the Little Ice Age of 1300 to 1900 A.D. were worldwide phenomena not limited to the European and North American" continents. http://www.cfa.harvard.edu... The hockey stick was used as the basis of claiming that there is a clear trend: temperatures are soaring exponentially, and because it was allegedly unprecedented, we should expect that to continue. So have they continued to soar exponentially since the late 90s? No, actually they have been trending downward since then. http://www.factsandarts.com... So if there is some miracle explanation that says it was correctly derived, we know for certain that using it to predict future climate trends, which was its sole purpose in the IPCC report, is bad science. The resolution is affirmed. **General conditions: (Perhaps I am taking this debate thing too seriously, but I have my own concept of fun.) Do not accept this debate challenge if you are interested in pressing a really creative lawyerly approach, like debating what the meaning of "is" is or interpreting the resolution in a way contrary to common sense. Legitimate semantic arguments are fine. If you think the resolution is unclear, ask in the Comments. Do not accept the challenge if you know nothing about the subject and don't plan to research it.