Proxy data in the context of "Global surface temperature"

Global surface temperature (GST) is the average temperature of Earth's surface at a given time. It is a combination of sea surface temperature and the near-surface air temperature over land, weighted by their respective areas. Temperature data comes mainly from weather stations and satellites. To estimate data in the distant past, proxy data can be used for example from tree rings, corals, and ice cores. Observing the rising GST over time is one of the many lines of evidence supporting the scientific consensus on climate change, which is that human activities are causing climate change. Alternative terms for the same concept are global mean surface temperature (GMST) or global average surface temperature.

Series of reliable temperature measurements in some regions began in the 1850—1880 time frame (this is called the instrumental temperature record). The longest-running temperature record is the Central England temperature data series, which starts in 1659. The longest-running quasi-global records start in 1850. For temperature measurements in the upper atmosphere a variety of methods can be used. This includes radiosondes launched using weather balloons, a variety of satellites, and aircraft. Satellites can monitor temperatures in the upper atmosphere but are not commonly used to measure temperature change at the surface. Ocean temperatures at different depths are measured to add to global surface temperature datasets. This data is also used to calculate the ocean heat content.