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The divergence problem is an anomaly from the field of dendroclimatology, the study of past climate through observations of old trees, primarily the properties of their annual growth rings. It is the disagreement between the temperatures measured by the thermometers (instrumental temperatures) and the temperatures reconstructed from the latewood densities or, in some cases, widths of tree rings in the far northern forests. While the thermometer records indicate a substantial warming trend, many tree rings from such sites do not display a corresponding change in their maximum latewood density. In some studies this issue has also been found with tree ring width.〔 〕 A temperature trend extracted from tree rings alone would not show any substantial warming. The temperature graphs calculated in these two ways thus "diverge" from one another since the 1950s, which is the origin of the term. ==Discovery== The problem of changing response of some tree ring proxies to recent climate changes was identified in Alaska by and . Tree ring specialist Keith Briffa's February 1998 study showed that this problem was more widespread at high northern latitudes, and warned that it had to be taken into account to avoid overestimating past temperatures.〔, 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「divergence problem」の詳細全文を読む スポンサード リンク
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