A climate anomaly is a difference between the observed climate value (such as temperature or precipitation) and the long-term average for the same location and time of year.
Put simply, it shows how unusual or extreme the current conditions are compared to what is considered “normal.”
How It Works
For example, if the average temperature in July over the past 30 years is 25°C, but this year it reaches 28°C, the anomaly is:
+3°C
If it’s colder than normal — say, 23°C — the anomaly is:
–2°C
Anomalies are typically calculated using a baseline period, such as 1951–1980 or 1991–2020, depending on the dataset (NASA, NOAA, ECMWF, etc.).
Why Are Climate Anomalies Important?
- They help scientists better track long-term climate change.
- They highlight unusual events like heatwaves, droughts, or heavy rainfall.
- They are commonly used in global climate reports and tools like NASA Earth Observatory and Copernicus Climate Data Store.
Saying “It was 28°C” gives less context than saying “It was 3°C above average.”
Examples of Climate Anomalies
- The global temperature anomaly in 2023 was +1.29°C, the highest ever recorded.
- Sea surface anomalies are used to track El Niño and La Niña events.
- Rainfall anomalies show drought zones or flooding patterns on a global scale.
How It’s Visualized
Climate anomaly maps often use color gradients:
- Blue tones = cooler or drier than average
- Red or orange = hotter or wetter than average
These visuals make it easier to see climate shifts and extreme events over time.
A climate anomaly reveals how the current climate differs from historical norms. It’s a powerful indicator of environmental change — and an essential tool for climate scientists, researchers, and the public.