A six-million-year speleothem derived clumped isotope temperature record of continental Eurasia

Our understanding of global temperature in the recent geological past is predominantly derived from oceanic proxies and modelling reconstructions1–3. Terrestrial proxy data, particularly in continental environments, is sparse and based largely on palaeobotanical and palaeozoological data which can be difficult to accurately date4.

We present approximately 30 temperature reconstructions over a six-million-year interval from Botovskaya Cave (N 55.3°, E 105.3°) in Siberia, ca. 300 km west of Lake Baikal. We provide chronological constraint with U-series techniques5 and multi-annual absolute temperature estimates from clumped isotope analyses of speleothems (carbonate cave deposits, e.g. stalagmites and flowstones). Clumped isotope analysis directly infers quantitative paleotemperature estimates, overcoming difficulties associated with conventional stable isotope (δ18O) techniques which require knowledge of the isotopic composition of carbonate precipitation waters – which is often unknown. By targeting subaqueous material, we overcome dis-equilibrium effects which have hindered widespread application of clumped isotopes to speleothems6,7.

Our record is the longest palaeotemperature timeseries from continental Eurasia and suggests a ca. 4 – 5°C temperature drop between the Messinian (7.24 – 5.33 Ma) and the present day, coincident with declining atmospheric carbon dioxide8, and in agreement with existing estimates of global temperature over the same interval9,10.