Isotope compositions of carbon and oxygen in calcite deposited to stalagmites are regarded as important proxies for paleo-climate. The number of papers reporting such proxies rises rapidly. Additionally cave monitoring is being performed to observe chemical properties of the water dripping to speleothems, the partial pressure of CO2 in the soil above the cave and in the cave atmosphere, and other parameters outside the cave to relate recent climate conditions to recently deposited calcite.
There are, however, physical and chemical processes independent of climatic conditions, which also contribute to the isotope composition and which can add noise to the climate signal. In this letter I resume these from the current literature to open a more easy access to this problem than available from the current original publications.