A temperature anomaly is calculated by subtracting the climate normal from the observed temperature. An anomaly of +3 °C means temperatures were 3 degrees above average; −5 °C, five degrees below.
Climate change indicator
Global anomalies are the fundamental indicator of global warming: the planet's average anomaly in 2024 was +1.5 °C relative to the pre-industrial period (1850–1900). On anomaly maps, red areas indicate abnormal warmth and blue areas abnormal cold, providing an at-a-glance view of which regions are experiencing extreme conditions.