![cover image](https://wikiwandv2-19431.kxcdn.com/_next/image?url=https://upload.wikimedia.org/wikipedia/commons/thumb/a/a0/20200324_Global_average_temperature_-_NASA-GISS_HadCrut_NOAA_Japan_BerkeleyE.svg/640px-20200324_Global_average_temperature_-_NASA-GISS_HadCrut_NOAA_Japan_BerkeleyE.svg.png&w=640&q=50)
Temperature anomaly
From Wikipedia, the free encyclopedia
For the recorded temperature change due to global warming, see Instrumental temperature record.
Temperature anomaly is the difference, positive or negative, of a temperature from a base or reference value, normally chosen as an average of temperatures over a certain reference or base period. In atmospheric sciences, the average temperature is commonly calculated over a period of at least 30 years over a homogeneous geographic region, or globally over the entire planet.
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/a/a0/20200324_Global_average_temperature_-_NASA-GISS_HadCrut_NOAA_Japan_BerkeleyE.svg/640px-20200324_Global_average_temperature_-_NASA-GISS_HadCrut_NOAA_Japan_BerkeleyE.svg.png)
Temperatures are obtained from surface and offshore weather stations or inferred from meteorological satellite data. Temperature anomalies can be calculated based on datasets of near-surface and upper-air atmospheric temperatures or sea surface temperatures.