Published: 6 October 2026. A climate reading needs three companions: its source, its reference period and its date. Without them, even an accurate number can tell the wrong story.
Our homepage climate indicator uses NASA’s GISTEMP v4 monthly global temperature analysis. This guide explains how to read it and why a single figure should be the start of an investigation.
What is a temperature anomaly?
An anomaly is the difference from a reference average. NASA GISS uses 1951–1980 as its baseline. A positive anomaly indicates warmer conditions relative to that period, rather than the Earth’s absolute temperature. The analysis combines land air-temperature observations and ocean surface-temperature measurements. Source: NASA GISS FAQ.
For example, a displayed value of +1.40°C means 1.40°C above the stated reference average. It does not mean that the planet’s temperature is 1.40°C, or that every place experienced the same increase.
Why the baseline matters
Our meter’s 1951–1980 baseline differs from the 1850–1900 period commonly used for pre-industrial comparisons. Numbers measured against these periods cannot be compared directly. Changing the baseline changes the numerical anomaly; it does not remove the underlying temperature trend. Source: NASA GISS.
Before sharing a headline number, ask “above what?” It is a small question that prevents a large misunderstanding.
Does one month above 1.5°C break the Paris Agreement threshold?
The Paris Agreement’s temperature goals concern long-term warming above pre-industrial levels. WMO explains that these levels are assessed over decades, typically using a 20-year period. An individual month or year exceeding 1.5°C is therefore different from a sustained long-term exceedance. Our meter also uses a different baseline. Source: WMO’s explanation, published 28 May 2025.
Why look beyond the latest reading?
A monthly update is a snapshot. Compare it with longer records and annual averages before drawing conclusions. NASA may revise earlier values as late observations and updated analysis become available. Source: NASA GISS FAQ.
A lower reading next month would not, by itself, show that the climate problem had been solved. A higher one would not tell us everything about conditions where we live. Careful interpretation requires context.
What the meter cannot show
Global temperature is one indicator. WMO connects additional warming with increasing risks from heatwaves, heavy rainfall, drought, ice loss and sea-level rise. A global average cannot describe every regional impact or replace a local forecast. Source: WMO.
What to read next
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Use our meter to open the conversation, then follow the evidence. The month shown is the month measured; the check date records when our system last consulted the source. Explore NASA’s full GISTEMP record, read our Doomsday Clock guide, or continue through Science & Signs.