Changes

'''YAD06''' is a tree growing in the Yamal Peninsula of Siberia. A core sample from this tree, YADO61, provided data used to support Michael Mann's [[hockey stick]] interpretation of global climate history. Mann's graph was first published in 1998. It shows global temperatures as stable for 900 years until the 20th century, when carbon dioxide emissions supposedly caused a rapid increase in global temperature. Mann created the graph to address reconstructions made by earlier climatologists that show a [[Medieval Warm Period]] between 950 and 1150. These reconstructions suggest that the climate was somewhat warmer at that time than it is at present. Although Ma nn claimed to have used a dozen proxies, analysis showed that only the data from YAD06 had the hockey stick pattern that Mann reported as his result.

'''YAD06''' is a tree growing in the Yamal Peninsula of Siberia. A core sample from this tree, YADO61, provided data used to support Michael Mann's [[hockey stick]] interpretation of global climate history. Mann's graph was first published in 1998. It shows global temperatures as stable for 900 years until the 20th century, when carbon dioxide emissions supposedly caused a rapid increase in global temperature. Mann created the graph to address reconstructions made by earlier climatologists that show a [[Medieval Warm Period]] between 950 and 1150. These reconstructions suggest that the climate was somewhat warmer at that time than it is at present. Although Ma nn claimed to have used a dozen proxies, analysis showed that only the data from YAD06 had the hockey stick pattern that Mann reported as his result.

Compared to other samples taken Yamal, the YAD061 core was an outliner by a factor of 8 sigma.<ref>Watts, Anthony,"[http://wattsupwiththat.com/2009/10/01/response-from-briffa-on-the-yamal-tree-ring-affair-plus-rebuttal/ Response from Briffa on the Yamal tree ring affair – plus rebuttal]," ''Watts Up With That?'', October 1, 2009.</ref> YAD06 may have grown more slowly than other trees when it was in the shade. When these other trees died, YAD06 would have received more sunlight, allowing its growth rate to accelerate.<ref>[http://borepatch.blogspot.tw/2009/10/yad061.html YAD061], ''Borepatch'',  October 3, 2009.</ref> Older trees tend to grow more slowly, quite apart from sunlight and climate issues. So the validity of tree ring data as a proxy for temperature is suspect.<ref>Watts, Anthony, "[http://wattsupwiththat.com/2013/08/16/oh-mann-paper-demonstrates-that-tree-ring-proxy-temperature-data-is-seriously-compromised/ Oh Mann! Paper demonstrates that tree-ring proxy temperature data is ‘seriously compromised’]", ''Watts Up With That?'', August 16, 2013.</ref>

Compared to other samples taken Yamal, the YAD061 core was an outliner by a factor of 8 sigma.<ref>Watts, Anthony,"[http://wattsupwiththat.com/2009/10/01/response-from-briffa-on-the-yamal-tree-ring-affair-plus-rebuttal/ Response from Briffa on the Yamal tree ring affair – plus rebuttal]," ''Watts Up With That?'', October 1, 2009.</ref> YAD06 may have grown more slowly than other trees when it was in the shade. When these other trees died, YAD06 would have received more sunlight, allowing its growth rate to accelerate.<ref>[http://borepatch.blogspot.tw/2009/10/yad061.html YAD061], ''Borepatch'',  October 3, 2009.</ref> Older trees tend to grow more slowly, quite apart from sunlight and climate issues. This factor is not usually taken into account, so the validity of using tree ring data as a proxy for temperature is suspect.<ref>Watts, Anthony, "[http://wattsupwiththat.com/2013/08/16/oh-mann-paper-demonstrates-that-tree-ring-proxy-temperature-data-is-seriously-compromised/ Oh Mann! Paper demonstrates that tree-ring proxy temperature data is ‘seriously compromised’]", ''Watts Up With That?'', August 16, 2013.</ref>

The Yamal samples were collected by two Russian scientists, Hantemirov and Shiyatov. However, their findings did not show anything resembling a hockey stick pattern. The Yamal data was rejiggered by Steven Briffa to fit a hockey stick pattern and published in 2000. Briffa's paper was seized upon by Mann and other researchers who found the MWP to be an inconvenience.

The Yamal samples were collected by two Russian scientists, Hantemirov and Shiyatov. However, their findings did not show anything resembling a hockey stick pattern. The Yamal data was rejiggered by Steven Briffa to fit a hockey stick pattern and published in 2000. Briffa's paper was seized upon by Mann and other researchers who found the MWP to be an inconvenience.