To date, independent analysis of climate data reported in the blogosphere has uncovered two major problems with the math used by official sources. The first, discovered in the fall of 2004, was a data filter biased to find what it was looking for. The second, reported this morning, is a Y2K computer error that bumped all the data upward beginning in January 2000.

Errors in the analysis of climate data have been documented for some time, notably beginning with this exposé in October, 2004 in Technology Review:

Global Warming Bombshell
By Richard Muller  |  October 15, 2004

A prime piece of evidence linking human activity to climate change turns out to be an artifact of poor mathematics.

….In the scientific and political debate over global warming, the latest wrong piece may be the hockey stick, the famous plot … published by University of Massachusetts geoscientist Michael Mann and colleagues. This plot purports to show that we are now experiencing the warmest climate in a millennium, and that the earth, after remaining cool for centuries during the medieval era, suddenly began to heat up about 100 years ago–just at the time that the burning of coal and oil led to an increase in atmospheric levels of carbon dioxide.

….Unfortunately, discussion of this plot has been so polluted by political and activist frenzy that it is hard to dig into it to reach the science….

But now a shock: Canadian scientists Stephen McIntyre and Ross McKitrick have uncovered a fundamental mathematical flaw in the computer program that was used to produce the hockey stick. In his original publications of the stick, Mann purported to use a standard method known as principal component analysis, or PCA, to find the dominant features in a set of more than 70 different climate records.

But it wasnt so. McIntyre and McKitrick obtained part of the program that Mann used, and they found serious problems. Not only does the program not do conventional PCA, but it handles data normalization in a way that can only be described as mistaken.

Now comes the real shocker. This improper normalization procedure tends to emphasize any data that do have the hockey stick shape, and to suppress all data that do not….

Recently, the story of bad math has gotten worse, much worse. This morning Daily Tech carried an article describing additional data scrutiny by Stephen McIntyre that shows a Y2K discontinuity in the climate data for one of the reporting regions in North America:

Blogger Finds Y2K Bug in NASA Climate Data
by Michael Asher  |  August 9, 2007 11:49 AM

Years of bad data corrected; 1998 no longer the warmest year on record

My earlier column this week detailed the work of a volunteer team to assess problems with US temperature data used for climate modeling. One of these people is Steve McIntyre, who operates the site climateaudit.org. While inspecting historical temperature graphs, he noticed a strange discontinuity, or “jump” in many locations, all occurring around the time of January, 2000.

These graphs were created by NASA’s Reto Ruedy and James Hansen (who shot to fame when he accused the administration of trying to censor his views on climate change). Hansen refused to provide McKintyre with the algorithm used to generate graph data, so McKintyre reverse-engineered it. The result appeared to be a Y2K bug in the handling of the raw data.

McKintyre notified the pair of the bug; Ruedy replied and acknowledged the problem as an “oversight” that would be fixed in the next data refresh.

NASA has now silently released corrected figures, and the changes are truly astounding. The warmest year on record is now 1934. 1998 (long trumpeted by the media as record-breaking) moves to second place. 1921 takes third. In fact, 5 of the 10 warmest years on record now all occur before World War II. Anthony Watts has put the new data in chart form, along with a more detailed summary of the events.

The effect of the correction on global temperatures is minor (some 1-2% less warming than originally thought), but the effect on the US global warming propaganda machine could be huge.

Then again– maybe not. I strongly suspect this story will receive little to no attention from the mainstream media.

Can we trust our government sources? No. As my dad used to say, ignorance is not rationed.

Can we trust the Blogosphere? Over time, yes. Because the Blogosphere is the largest pool of subject matter experts the world has ever seen. We are a

• totally networked
• dynamically interactive
• mutually vetting

congregation of legal experts, physicists and mathematicians, futurists, military experts, grammarians, historians, political analysts, linguists, geographers, economists, sociologists, doctors, philosophers, computer experts, media and communications specialists, and skilled practitioners of every discipline under the sun. The Blogoshpere is a consummate research department.

Also check out this article — Did Media Or NASA Withhold Climate History Data Changes From The Public? by Noel Sheppard at NewsBusters.