Global surface temperature

Global surface temperature (GST) refers to the average temperature of Earth's surface. It is determined nowadays by measuring the temperatures over the ocean and land, and then calculating a weighted average. The temperature over the ocean is called the sea surface temperature. The temperature over land is called the surface air temperature. 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.

This article is about the average temperature at the Earth's surface, in general. For more specific temperature information recorded since the advent of modern scientific monitoring (since about 1850), see Instrumental temperature record.

Alternative terms for the same thing are global mean surface temperature (GMST) or global average surface temperature.

Series of reliable global temperature measurements began in the 1850—1880 time frame (this is called the instrumental temperature record). Through 1940, the average annual temperature increased, but was relatively stable between 1940 and 1975. Since 1975, it has increased by roughly 0.15 °C to 0.20 °C per decade, to at least 1.1 °C (1.9 °F) above 1880 levels. The current annual GMST is about 15 °C (59 °F), though monthly temperatures can vary almost 2 °C (4 °F) above or below this figure.

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