The warmest summers in the last seven millennia have been recorded in Northwest Siberia. After a long period of general cooling over many millennia, a sharp reversal began in the 1800s, with temperatures climbing rapidly and reaching peaks in recent decades. The finding was published recently in Nature Communications.
Dendrochronologists working with the Institute of Animal and Plant Ecology at the Ural Branch of the Russian Academy of Sciences and with Ural Federal University collected subfossil wood through decades of field expeditions. Their effort established a remarkably long chronology of tree-ring widths for the Yamal region, enabling climate insights spanning thousands of years.
With support from colleagues at the University of East Anglia, the Swiss Federal Institute for Forest, Snow and Landscape Research, and the Climate Research Unit at the University of Geneva, researchers analyzed the tree rings to reconstruct summer temperatures with annual precision over the past 7,638 years.
Working area and thermal anomalies Nature
According to lead researcher Rashit Hantemirov, shifts in Earth’s orbital dynamics would typically predict a gradual decline in summer solar energy and temperature in subpolar latitudes of the Northern Hemisphere for the last 8,000 to 9,000 years. In the Yamal region, however, the cooling trend was interrupted in the mid-19th century as temperatures rose sharply, culminating in the highest values seen in recent decades.
Across any period examined, from 30 to 170 years, the warmest interval stood out as the closest one in time. The record shows not only unprecedented warmth but also a pace of warming never observed before the mid-1800s.
Researchers noted that the last century featured a striking absence of extreme cold, with 27 years of extreme heat and 19 of these occurring in the last 40 years, reinforcing the view that recent warming is extraordinary. These patterns align with a growing consensus that human activities influence climate change, at least in north-west Siberia.
Future climate reconstruction work will continue, with the potential to extend the Yamal tree-ring chronology by another two millennia as data accumulate and methods improve over time.
Research team members
International collaboration is expanding the toolkit for climate studies beyond tree rings. In ongoing efforts from Switzerland and elsewhere, researchers are analyzing cellular structures within annual rings and exploring the oxygen-18 isotope composition in tree tissues to further refine reconstructions of past climate conditions.
Stepan Shiyatov, a pioneer of dendrochronology in Russia, initiated systematic subfossil wood collections on the Yamal Peninsula more than forty years ago. Since then, more than two dozen expeditions have yielded a repository of over 5,000 specimens at the Institute of Animal and Plant Ecology.
Approximately 2,000 larch and spruce subfossil samples have also undergone dating using cross-dating methods. This work assigns an exact formation year to each annual ring for the last 8,800 years, making it the longest tree-ring chronology in polar regions.
Tree rings serve as one of the best natural archives of past environmental conditions, including air temperature. Trees in subpolar zones and at high altitudes are highly responsive to temperature changes. The Yamal specimens provide a window into ancient climates, forming a robust basis for predicting future trends.
Reference work: https://www.nature.com/articles/s41467-022-32629-x
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