evidence: In comparison, the global mean surface air temperature (GSAT) is the "global average of near-surface air temperatures over land, oceans and sea ice. Changes in GSAT are often used as a measure of global temperature change in climate models."[10]: 2231 [...] Scientists use several methods to predict the effects of human-caused climate change. One is to investigate past natural changes in climate.[25] To assess changes in Earth's past climate scientists have studied tree rings, ice cores, corals, and ocean and lake sediments.[26] These show that recent temperatures have surpassed anything in the last 2,000 years.[27] By the end of the 21st century, temperatures may increase to a level last seen in the mid-Pliocene. This was around 3 million years ago.[28]: 322 At that time, mean global temperatures were about 2–4 °C (3.6–7.2 °F) warmer than pre-industrial temperatures. The global mean sea level was up to 25 metres (82 ft) higher than it is today.[29]: 323 The modern observed rise in temperature and CO2 concentrations has been rapid. Even abrupt geophysical events in Earth's history do not approach current rates.[30]: 54Methods [edit]The instrumental temperature record is a record of temperatures within Earth's climate based on direct measurement of air temperature and ocean temperature. Instrumental temperature records do not use indirect reconstructions using climate proxy data such as from tree rings and marine sediments.[31]