September 2026 Climate Baseline: July Heat, 429.12 ppm CO2, and Arctic Ice at 8.29 Million km²

The September 5 reporting cut-off finds four indicators at four different points in their release cycles. NOAA's latest complete global temperature and Mauna Loa CO₂ observations are for July 2026. The latest complete monthly Arctic sea-ice value is also for July, while the newest Arctic daily snapshot is from August 2. NASA's latest public global mean sea-level snapshot is dated August 2026. The figures below keep each agency's baseline and product label intact.

NOAA's July 2026 global surface temperature was 1.18°C above the 20th-century average, equal to 2.12°F. July 2026 tied July 2024 as the warmest July in NOAA's record. January through July 2026 ranked third-highest for that seven-month period. 1

The same NOAA series puts June 2026 at +1.09°C and July 2025 at +1.00°C. July 2026 was therefore 0.09°C warmer than June and 0.18°C warmer than July 2025 within this single baseline. 123

Copernicus's July bulletin, summarized by the World Meteorological Organization, places July 2026 at 1.47°C above the estimated 1850–1900 pre-industrial level and ranks it second-warmest globally, tied with July 2024 in that product. The NOAA and Copernicus numbers use different reference periods, so the two anomalies should remain separate. 4

A monthly anomaly above 1.5°C supplies a clear measure of current heat. The Paris temperature thresholds describe long-term warming, so one month does not establish a permanent crossing of either threshold. The July reading belongs in the cumulative trajectory alongside emissions and multi-year averages.

NOAA's Global Monitoring Laboratory reports a 429.12 ppm monthly mean at Mauna Loa for July 2026. July 2025 was 427.87 ppm, making the year-on-year increase 1.25 ppm. The page was last updated on August 5, 2026, and the latest year's values remain preliminary while NOAA completes recalibration and quality-control checks. 5

The Mauna Loa record began in 1958 and remains the longest direct record of atmospheric CO₂. NOAA calculates each monthly mean from daily means gathered during background conditions. Mauna Loa is a high-altitude northern-subtropical station, so its monthly value is a station record rather than a globally averaged surface concentration. 5

The current public trend page exposes July 2026 and July 2025 directly. It does not expose a clean June 2026 value in the same visible table, so this edition leaves the month-on-month field open rather than deriving it from a separate snapshot. The associated NOAA dataset page identifies the downloadable record as version 2026-08-11 with DOI 10.15138/yaf1-bk21, while its listed time coverage ends in December 2025. 58

NASA's public Earth indicator reports 100.7 ± 4.0 mm for August 2026. The satellite record tracks global mean sea-level change from 1993 onward and includes a seasonal cycle caused by water moving between land and ocean. NASA's current rate is 0.44 cm per year, compared with 0.20 cm per year in 1993. 6

The public indicator gives the August point and the long-term rate, while the rendered snapshot does not expose paired August-to-July or August-to-August values. This edition keeps both comparison fields unavailable. The underlying PO.DAAC collection, NASA_SSH_GMSL_INDICATOR, is Version 1, covers January 4, 1993 to the present, and carries DOI 10.5067/NSIND-GMSV1. 9

NASA attributes roughly two-thirds of current sea-level rise to melting land ice and one-third to ocean warming. The August point therefore belongs beside the rate change since 1993: the monthly value moves with the seasonal cycle, while the multi-decadal record shows the longer rise. 6

The Met Office's August briefing, using the EUMETSAT OSI SAF Sea Ice Index, gives a July 2026 mean Arctic extent of 8.29 million km². July was joint fifth-lowest for the month in the satellite record. The value was 1.55 million km² below the 1981–2010 average, and the average July loss rate was 86,000 km² per day, compared with 80,000 km² per day for 1981–2010. 7

The same briefing places daily Arctic extent at 7.02 million km² on August 2, 1.38 million km² below the 1981–2010 average and ninth-lowest for that date since the satellite record began in 1979. The August 2 value is a daily snapshot; the 8.29 million km² value is a July monthly mean. 7

Copernicus's July bulletin ranks Arctic sea ice sixth-lowest for the month. The OSI SAF/Met Office joint-fifth ranking and the Copernicus sixth-lowest ranking describe different products, so the product name belongs with each rank. The current briefing also leaves clean same-product June and July 2025 comparators unavailable. 710

NOAA's Climate Prediction Center issued its ENSO Diagnostic Discussion on August 13, 2026. The discussion reports a July Niño-3.4 index of +1.4°C, eastern equatorial Pacific sea-surface temperature anomalies above +2.0°C, and a greater-than-90% chance of a very strong El Niño during the Northern Hemisphere fall and winter of 2026–27. NOAA assigns a 69% chance during October–December 2026 to a historic event, defined there as a three-month RONI of at least +2.5°C, exceeding prior events in the record back to 1950. 11

These probabilities describe a forecast, while the four rows above describe observed temperature, CO₂, sea level, and sea ice. El Niño may affect the timing and regional pattern of upcoming heat and precipitation, but the forecast belongs beside the measured baseline rather than inside it. 11

The IPCC's AR6 WGIII Figure 2.7 frames 1.5°C and 2°C through remaining carbon budgets. The figure reports budgets as of January 1, 2020, at the 67th percentile, with an uncertainty of ±220 GtCO₂-equivalent for each budget. 12

The Global Carbon Budget 2025 update supplies a newer estimate as of January 2026: 170 GtCO₂ for 1.5°C, 525 GtCO₂ for 1.7°C, and 1,055 GtCO₂ for 2°C. At current emissions, the update translates those estimates into roughly four, 12, and 25 years. These figures are a supplement to the IPCC framework, with different dating and methodology; they are not an IPCC deadline. 13

The four monthly indicators describe the state of the climate system; the carbon budget describes the cumulative emissions constraint. July's temperature ranking, July's 429.12 ppm Mauna Loa reading, the August sea-level snapshot, and the low Arctic ice extent all belong to that longer accounting, while each remains tied to its own measurement system and release date.

The September baseline therefore has four firm latest observations, three direct year-on-year or ranking comparisons, and clearly marked open comparison fields. The open fields reflect release timing and public dashboard structure; the measured values remain tied to their named products, dates, and baselines.