How to Read NASA's GISTEMP Global Temperature Table — Anomalies, Baselines and Monthly Uncertainty

As of 10 November 2026, 01:47 KST (retrieved by this page at that time); latest listed on the agency page at retrieval: the global Land-Ocean Temperature Index table of NASA's GISS Surface Temperature Analysis (GISTEMP v4), reached from the GISTEMP page through its data page. The table header lists sources through 09/2026, so September 2026 is its latest month; the release schedule set September's update for Fri, 9 Oct 2026. The table itself carries no date. Primary source: https://data.giss.nasa.gov/gistemp/tabledata_v4/GLB.Ts+dSST.txt^[1][2][4]

Comparison basis: the table prints anomalies in hundredths of a degree Celsius, rounded to whole units, relative to 1951-1980; this page divides by 100 and subtracts the displayed values. The table note says: Divide by 100 to get changes in degrees Celsius (deg-C), and multiply that result by 1.8 for degrees Fahrenheit, so 1.38°C is about 2.48°F. The FAQ gives the size of the uncertainty: "Roughly speaking, the uncertainty of annual global means after 1960 is about ±0.05°C, for seasonal and monthly means that number increases to ±0.1°C and ±0.17°C, respectively." It does not state a confidence level.^[1][3]

In three lines

1. Global surface temperature in September 2026 was 1.38°C above the 1951-1980 average in GISTEMP v4, second among the September estimates in the table after 2023 (1.48°C), by this page's ranking.
2. That is 0.14°C above September 2025 (1.24°C) and 0.04°C below August 2026 (1.42°C), first among the August estimates by the same ranking.
3. The October 2026 update was scheduled for Thu, 12 Nov 2026 (release schedule [4]).^[1][4]

An estimate of change, not an absolute temperature. "The GISS Surface Temperature Analysis version 4 (GISTEMP v4) is an estimate of global surface temperature change." "For the GISS analysis, normal always means the average over the 30-year period 1951-1980 for that place and time of year." "This base period is specific to GISS, not universal." The FAQ also answers no to whether the month with the highest anomaly is the warmest month overall, because of the seasonal cycle.^[2][3]

Inputs. The page names NOAA's GHCN v4 station data and ERSST v5 ocean data; the FAQ adds: "Satellite data are not used although they do provide global coverage."^[2][3]

Pre-industrial comparisons need an extra step. For a 1850-1900 baseline the FAQ describes an adjustment and says: "This is equivalent (as of Jan 2025), of adding ~0.19ºC." It adds that these numbers may change and: "Note also, that anomalies with respect to the pre-industrial are more uncertain than anomalies w.r.t. a modern baseline." This page does not convert the table to that baseline.^[3]

Two annual columns. J-D is the calendar year; D-N runs from December to November, which matches the FAQ's meteorological year: "String these four seasons together and you have the meteorological year that begins on Dec. 1 and ends on Nov. 30." For 2025 the two columns read 1.18 and 1.20.^[1][3]

NASA 1.38°C and NOAA 1.33°C for the same month. NOAA's NCEI reported: "The global surface temperature in September 2026 was 2.39°F (1.33°C) above the 20th-century average—the second-warmest September in the 1850–2026 record, trailing behind the 2023 record by 0.13°F (0.07°C)." GISTEMP measures from 1951-1980 and NOAA from the 20th-century average, with different analysis methods, so the two figures are different measures. Because baselines and analysis methods differ, the difference between the two figures alone does not indicate a disagreement about the month. NOAA places September 2026 second behind 2023 in its own record; this page's ranking of the NASA table also puts it second, 0.10°C below 2023.^[1][5]

Second by the estimates shown. By the estimates shown, September 2026 ranks second, 0.10°C below September 2023; the FAQ's roughly ±0.17°C for monthly means alone does not determine the statistical certainty of the difference between two months. The same caution applies to August 2026, which this page's ranking of the table puts first among Augusts, 0.12°C above August 2024 (1.30).^[1][3]

Earlier months move. The page says: "These updated files incorporate reports for the previous month and also late reports and corrections for earlier months." The FAQ explains: "These occasional corrections are one reason why monthly updates not only add e.g. global mean estimates for the new month, but may slightly change estimates for earlier months." The August 2026 value of 1.42 is as printed in the table retrieved here; the table posted with the August update was not retrieved, so whether August changed is not established.^[2][3]

Year to date. NOAA wrote: "Looking at the year-to-date, the January–September global surface temperature was the second highest on record behind 2024." NOAA thus reported 2026 as second only to 2024 in its own record. Averaging the January to September cells of GISTEMP gives 1.28 for 2024, 1.23 for 2026 and 1.20 for 2025, the same order; these averages are this page's calculation, not GISS figures.^[1][5]

Dates kept apart. Data: through September 2026 (sources 1880-09/2026 in the header). September update: scheduled for Fri, 9 Oct 2026. NOAA's September global release: published October 9, 2026. GISTEMP page: latest news item September 14, 2026. Release schedule page: updated Feb 3, 2026.^[1][2][4][5]

Next release. The schedule page says: "As of Jan. 30, 2026, we plan to release the monthly GISTEMP analysis updates during 2026 on the dates given below simultaneously with NOAA/NCEI's releases of their monthly Global Analysis." It lists the October Release for Thu, 12 Nov 2026, 11:00 AM EST and the November Release for Wed, 9 Dec 2026, 11:00 AM EST; these are planned dates.^[4]