How CRU Cooked the Books on Siberia

We learned in December 2009 from the Russian newspaper RIA Novosti that Hadley CRU had tampered with Russian temperature data by including only 25% of available weather stations in its reports: 

"Climategate has already affected Russia. On Tuesday, the Moscow-based Institute of Economic Analysis (IEA) issued a report claiming that the Hadley Center for Climate Change...had probably tampered with Russian climate data. The IEA believes that Russian meteorological-station data did not substantiate the anthropogenic global-warming theory.

Analysts say Russian meteorological stations cover most of the country's territory, and that the Hadley Center had used data submitted by only 25% of such stations in its reports. Over 40% of Russian territory was not included in global-temperature calculations for some other reasons, rather than the lack of meteorological stations and observations.

The data of stations located in areas not listed in the Hadley Climate Research Unit Temperature UK (HadCRUT) survey often does not show any substantial warming in the late 20th century and the early 21st century.

The HadCRUT database includes specific stations providing incomplete data and highlighting the global-warming process, rather than stations facilitating uninterrupted observations. On the whole, climatologists use the incomplete findings of meteorological stations far more often than those providing complete observations. IEA analysts say climatologists use the data of stations located in large populated centers that are influenced by the urban-warming effect more frequently than the correct data of remote stations.

The scale of global warming was exaggerated due to temperature distortions for Russia accounting for 12.5% of the world's land mass. The IEA said it was necessary to recalculate all global-temperature data in order to assess the scale of such exaggeration."

Turns out, not only did HADCRU cook the books by selecting stations with incomplete data and only 25% of the available stations, they used another trick* of selecting 1976 as the base year (at the end of the global cooling scare) to begin their time series for Siberia, even though they had data back to 1936. As reported by an Italian Climate Blog, this resulted in a much more alarming trend line:

*"trick" is defined by Michael Mann as "a clever way to solve a problem"