Modern Warming Is the Strongest in 7,000 Years

12:36, August 26, 2022

Findings are based on data from the annual rings of semi-fossil trees on Yamal Peninsula [photo report]

The summer seasons of the last decades in the north of Western Siberia turned out to be the warmest for the last 7,000 years. In previous millennia, air temperatures had been dropping gradually, with fluctuations in one direction or the other. However, in the XIX century began to rise and in recent decades reached the highest numbers. This was found out by the dendrochronologists of the Institute of the Plant and Animal Ecology, Ural Branch, Russian Academy of Sciences and Ural Federal University, who spent 40 years creating a superlong tree-ring chronology, based on the width of the annual rings of semi-fossil trees on Yamal Peninsula. During this time, they were able to study information on summer temperatures for 7,638 years. The scientists published the results of the study and their findings about temperatures in Western Siberia in the journal Nature Communications. The research is supported by the Russian Science Foundation (project No. 21-14-00330).

"Due to cyclic changes in the orbital parameters of the Earth in the circumpolar latitudes of the Northern Hemisphere there is a gradual decrease of solar energy in the summer months. This phase began about 8-9 thousand years ago and continues now. However, the data of annual rings show that since the middle of the 19th century the trend began to change, the temperature began to rise very rapidly. It reached the highest values in last decades," explains Rashit Hantemirov, Leading Researcher at the Laboratory of Dendrochronology of Institute of the Plant and Animal Ecology, Ural Branch, Russian Academy of Sciences and UrFU Laboratory of Natural Science Methods in Humanities.

Whatever period of time in the interval from 30 to 170 years was taken by the researchers, the warmest was the one that ended with the last year of reconstruction. For example, the average value for the last century is higher than the temperature of any other randomly taken centennial interval in the past.

"The rate of temperature increase in recent decades is not too fast when considering relatively short time scales. On the 160-170 year interval, however, the rate of current warming is the fastest compared to what we have seen in the past. The exceptionality of current warming is also evidenced by the fact that in the last century, there have been no extremely cold summers, but there have been 27 extremely warm years. Of these, 19 were in the last 40 years, that is, every second year in these decades was extremely warm," says Rashid Hantemirov.

Scientists believe the data show that anthropogenic factors have not only added to the list of major forces influencing climate change, but have become more determinative than natural causes.

Research on climatic chronology will continue, assures Rashit Hantemirov. Scientists plan to extend the reconstruction of the climate into the past by another 2 thousand years. Colleagues from the Climate Research Department of the University of East Anglia, the world's best specialists in extracting information about centuries-old fluctuations, are helping in this. Experts from the Swiss Federal Institute for Forest, Snow and Landscape Research, as well as colleagues from the University of Geneva supported the study in evaluating and visualizing the findings.

"International cooperation will make it possible to use other parameters of tree rings for climatic reconstructions. Together with colleagues from Switzerland, we are working on the analysis of intracellular structures of annual rings. On the basis of the Institute of Geology and Geophysics of the Chinese Academy of Sciences it is planned to carry out climatic reconstruction based on the analysis of oxygen isotope-18 in the annual rings of trees on Yamal," explains Rashit Hantemirov.

Reference

40 years ago Stepan Shiyatov, a founder of dendrochronology in Russia, began with colleagues from the Institute of the Plant and Animal Ecology, Ural Branch, Russian Academy of Sciences, systematic collections of semi-fossil wood on the Yamal Peninsula. He was the first to recognize the value of the information stored in the annual rings of ancient trees for the reconstruction of climate history. Over the years, more than two dozen expeditions have been conducted, more than 5,000 saw cuts from semi-fossil trees have been collected, and the width of their annual rings has been measured.

The method of cross-dating determined with absolute precision the dates of formation of each ring in about two thousand larches and spruces, which grew on the peninsula during the last 8.8 thousand years, and created the longest for the circumpolar regions tree-ring chronology.

Annual tree rings are one of the best sources of past air temperature data by many criteria. The most temperature-sensitive trees grow in the circumpolar regions and high mountains. In some polar regions, there are remnants of trees that lived thousands of years ago. One such place is the Yamal Peninsula.

• Expedition to the Yamal Peninsula

The news article was translated by UrFU International Marketing Office
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