Climate change: Yamal tree rings I. Background

Yamal Peninsula has recently become famous due to controversial in climate change researches. A recent article in the prestigious journal  Science reconstructs the Arctic average temperature over the last two millennia. The report shows a brutal oddly soaring temperatures in the twentieth century.

Jump back scientific controversy about the dreaded global warming. The climate change summit in Copenhagen (Denmark) this December is approaching and with it come new studies to justify the threat of polluting gases emissions (CO2) by man into the atmosphere.

The report shows a brutal oddly soaring temperatures in the twentieth century. A new hockey stick based on data provided by tree rings from the Yamal Peninsula in Siberia, as a witness in climate.

The target de jour is a particular compilation of trees (called a chronology in dendro-climatology) that was first put together by two Russians, Hantemirov and Shiyatov, in the late 1990s (and published in 2002). This multi-millennial chronology from Yamal (in northwestern Siberia) was painstakingly collected from hundreds of sub-fossil trees buried in sediment in the river deltas. They used a subset of the 224 trees they found to be long enough and sensitive enough (based on the interannual variability) supplemented by 17 living tree cores to create a “Yamal” climate record.

A preliminary set of this data had also been used by Keith Briffa in 2000 (pdf) (processed using a different algorithm than used by H&S for consistency with two other northern high latitude series), to create another “Yamal” record that was designed to improve the representation of long-term climate variability.

Popularized by Al Gore, the hockey stick graph shows a precipitous rise in global temperatures over the last few decades. Using the hockey stick graph as a base, Gore extrapolated the data to claim that catastrophic temperature change (with all of its deleterious effects) was around the corner. This claim has been adopted with religious zeal by some scientists, almost all international politicians, and the Obama administration. As a consequence, massive worldwide policy initiatives are being developed. The question is—are they being developed to solve a problem that has been improperly characterized and incompletely understood.

As for assessing the significance of 20th century global warming, the evidence from dendroclimatology in general, supports the notion that the last 100 years have been unusually warm, at least within a context of the last two millenia. However, this evidence should not be considered equivocal. The activities of humans may well be impacting on the 'natural' growth of trees in different ways, making the task of isolating a clear climate message subtly difficult.

This long-term trend was caused by the steady orbitally driven reduction in summer insolation. The cooling trend was reversed during the 20th century, with four of the five warmest decades of our 2000-year-long reconstruction occurring between 1950 and 2000.

All these studies have been disqualified due to the data set used to conduct such research. In following post we will give further information about the controversial of Yamal tree rings, explaining more about this scientific affair.