Reference
Demezhko, D.Yu. and Shchapov, V.A. 2001. 80,000 years ground surface temperature history inferred from the temperature-depth log measured in the superdeep hole SG-4 (the Urals, Russia). Global and Planetary Change 29: 167-178.
What was done
Whereas most boreholes do not exceed 1 km depth, which limits the length of the ground surface temperature history reconstruction by this method to only the last few centuries, the authors studied a borehole extending to more than 5 km depth, allowing them to reconstruct an 80,000-year history of ground surface temperature. This borehole was located in the Middle Urals within the western rim of the Tagil subsidence (58°24' N, 59°44'E).
What was learned
The reconstructed temperature history revealed the existence of a number of climatic excursions, including the "Holocene Optimum 4000-6000 years ago, Medieval Warm Period with a culmination about 1000 years ago and Little Ice Age 200-500 years ago." Furthermore, the mean temperature of the Medieval Warm Period was determined to be more elevated above the mean temperature of the past century than the mean temperature of the Little Ice Age was reduced below that of the past century.
What it means
Once again, we have real-world evidence for the reality of the Medieval Warm Period, as well as its dominance over the past century in terms of its much greater warmth, which flies in the face of the contrary claims of climate alarmists who strive desperately to make current temperatures appear "unprecedented" over the past millennium.