As it is impossible to predict future climate development without knowing the driving forces and mechanisms of past climate change, all kinds of palaeoenvironmental and palaeoclimate archives in particular increasingly gain attention. Among terrestrial archives, carbonate sediments are of particular interest since they represent chemical precipitates reflecting environmental conditions in the moment of their formation, however, they are subject to structural, chemical and isotopical change when undergoing diagenetic processes. Most proxy definitions depend upon analogy with modern-day relationships, and their validity has long been questioned. Geological archives are, unfortunately, neither complete nor impartial witness to the past and even qualitative interpretations include inherent uncertainties that must be recognized and stated. High-resolution (monthly to decadal) carbonaceous proxies have high potential to reconstruct not only global and regional climate sensitivity, but also the response of local hydrology to climate change. Each high-resolution proxy type, however, is subject to a unique combination of uncertainties that obscure the climate signals. The crucial problem is that we know very little about both nature and scale of these uncertainties. For the palaeotemperature reconstruction from carbonates, most commonly used proxies are stable isotope composition of carbonate oxygen (δ18O) and its geochemical composition, in particular Mg/Ca and Sr/Ca ratios. Some uncertainties of these records will be presented for two hydrologically similar tufa precipitating systems in different climate areas in Croatia (Mediterranean) and Slovenia (continental climate) and for speleothems from Postojna cave (Slovenia), and some possibilities for their calibration will be discussed.
