Surface temperature trends in Russia over the past five centuries reconstructed from borehole temperatures

We analyze borehole temperature logs from 101 sites in Russia and nearby areas to reconstruct the ground surface temperature history (GSTH) over the past five centuries. The data are drawn principally from three regions: the Urals, southwest Siberia, and northeast Siberia. We derive GSTHs for each region individually, and a composite “all-Russia” GSTH from the full ensemble of sites. The results show that over the past 500 years, the investigated areas have on average warmed 1 K, with more than half of the warming occurring in the 20th century alone, and 70–80% in the 19th and 20th centuries taken together. The 16th through 18th centuries in the Urals and southwest Siberia were on average 0.1–0.2 K cooler than at the beginning of the 19th century, but northeast Siberia was more moderate in the 16th through 19th centuries, relative to the present-day, than the Urals or southwest Siberia. A wide variety of instrumental, proxy, and indirect evidence support these geothermal results.