The study of the relationships between annual tree growth and climate is called dendroclimatology. Dendroclimatology offers a high-resolution (annual) form of palaeoclimate reconstruction for the last few thousand years. Whenever tree growth is limited directly or indirectly by some climate element, usually temperature or rainfall, and that limitation can be quantified and dated, dendroclimatology can be used to reconstruct some information about past environmental conditions. There are several subfields of dendroclimatology associated with the processing and interpretation of different tree-growth variables. Such variables include tree ring width, tree ring density, and chemical or isotopic variables.