A temperature anomaly is the difference between a measured temperature and the average temperature for a specified reference period, location, and time.
An anomaly can be positive or negative. A positive temperature anomaly means the measured temperature is higher than the reference average, while a negative anomaly means it is lower. For example, if a location’s average temperature for a particular month is 25°C and the observed temperature is 27°C, the temperature anomaly is +2°C.
Temperature anomalies are useful because they allow scientists to compare changes across different locations without relying only on absolute temperatures. A temperature of 30°C, for instance, may be unusually hot in one region but relatively ordinary in another.
Scientists use temperature anomalies to monitor long-term warming, investigate climate patterns, and assess the effects of phenomena such as El Niño and La Niña. The value depends on the reference period used, so comparisons should account for differences in the baseline.
QUICK FACT
A temperature anomaly is a difference, not an absolute temperature. An anomaly of +2°C means that a measurement is 2°C above its reference average; it does not mean the actual temperature is 2°C.
COMMONLY CONFUSED WITH
- Absolute temperature: The actual measured temperature, such as 27°C.
- Global warming: The long-term increase in Earth’s average surface temperature. Temperature anomalies are one of the tools used to measure and communicate this change.
- Heat wave: A period of unusually hot weather relative to the conditions normally experienced in a particular area.
SEE ALSO