An international team of scientists from Russia, the United Kingdom and Israel found evidence of the fact that there was no permafrost on the Asian continent (up to the Arctic Ocean) in the past, when average global temperatures were 4.5 degrees higher than they are today.

Scientists employed the so-called high-precision uranium-lead dating method (that utilizes the radioactive decay of natural uranium and the formation of lead in carbonate layers) to determine the age of 60-plus samples found inside caves in the Lena River delta in northeastern Siberia.

According to the Russian Academy of Sciences, the authors of the study were able to determine the age of sedimentation layers inside caves of the Taba-Ba’astakh cliffs by measuring tiny amounts of elements at Oxford University laboratories. The minerals accumulated in northernmost Siberian territories 8.7 million years ago during the Late Miocene period. The presence of sedimentation deposits inside caves during that period shows that soil temperatures were above freezing, and that there were no perennial rock layers, which allowed water to seep though the soil.

Available data from other regions shows that, in the past, average global temperatures were 4.5 degrees higher on current levels. Consequently, this increase in temperature levels is enough to melt most permafrost from Asia to the Arctic Ocean.

The research results show that the climate is likely to change in the future. Permafrost might melt in the Northern Hemisphere if global temperatures continue to rise. This will release up to 130 billion metric tons of currently frozen carbon, thereby accelerating the global warming process.

The research was conducted over a period of more than 10 years and is part of a broader paleoclimatic and geocryological reconstruction of Eastern Siberia and Mongolia, launched in 2008.