Current climate weather station data, remote sensing, numerical modeling using general circulation models. Past climate proxy indicators, ice core, sediments, coral reefs, tree ring, etc. Isotope analysis a technique that uses the atomic structure of chemical elements, specifically the relative amounts of their isotopes to identify the chemical composition of past oceans and ice masses. Oxygen isotope analysis light oxygen in water moves poleward creating reservoirs rich in o16 on the land with o18 or heavy oxygen in ocean water. Ice cores extractive air from ice cores and analyzing how the air was hundreds of years ago looking at the oxygen isotope ratio. Short term climate reconstruction hundreds or thousands of years being analyzed, tools include radiocarbon dating, analysis of growth rings or trees, speleothems and corals. Tree rings drought and low sun = low growth creating small cells, high sun and moist = high growth creating large cells.