August 2026 Climate Baseline: June Heat, 431.44 ppm CO2, and July Sea Level

This edition is a 5 August 2026 snapshot. The latest observation is not the same month for every indicator: June is the newest complete month for global temperature, atmospheric CO2, and Arctic sea ice, while NASA's latest sea-level indicator point is dated July. June's global temperature remained near the top of the record, CO2 reached 431.44 ppm at Mauna Loa, Arctic sea ice was among the lowest June values in the satellite era, and NASA's sea-level indicator reached 102.4 mm above its 1993 reference.

Copernicus ERA5 puts June 2026's global mean surface air temperature at 16.54°C, or +0.56°C relative to 1991-2020 and +1.39°C relative to 1850-1900. That made June 2026 the second-warmest June in the C3S record, behind June 2024 and ahead of June 2023. The same dataset's July 2025-June 2026 average was +1.43°C relative to the pre-industrial reference. 1

NOAA's independent analysis tells the same ranking story on a different baseline: +1.96°F (+1.09°C) above the 20th-century average, the second-warmest June in NOAA's 1850-2026 record, behind 2024. January-June 2026 was the third-highest first half of a year in that record, and all ten of NOAA's warmest Junes have occurred since 2015. 2

Using NOAA's 20th-century baseline, June's +1.09°C was 0.02°C above May's +1.07°C and 0.11°C above June 2025's +0.98°C. 89 These are valid within NOAA's own series; they should not be combined arithmetically with the C3S anomalies, which use different coverage and reference periods.

The regional record was sharper than the global rank. C3S reported the warmest June on record for western Europe, while NOAA reported the highest June ocean temperature on record globally. 210

One interpretation matters for pathway reporting: a monthly value above 1.5°C is a warning about the trajectory, not a declaration that the Paris temperature limit has been permanently crossed. The policy threshold concerns a sustained long-term warming level. The C3S 12-month value is therefore more informative than any single month, but it still should not be presented as a formal threshold verdict.

NOAA's Mauna Loa monthly mean was 431.44 ppm in June 2026, based on 19 days of background observations. The file was generated on 5 July 2026, and NOAA notes that quality-control revisions can change values slightly. 3

The headline comparison is straightforward:

That is a 0.90 ppm month-to-month decrease and a 1.83 ppm year-on-year increase. The monthly decline is expected around the end of the Northern Hemisphere spring peak. NOAA's deseasonalized series moved from 429.10 ppm in May to 429.06 ppm in June, so the underlying comparison is nearly flat over this one-month interval rather than a 0.90 ppm reversal in the long-term trend. 3

Against the commonly used pre-industrial reference of approximately 280 ppm, June's value was 151.44 ppm higher, or about 54% above that level. This is a concentration comparison, not a direct conversion into a temperature anomaly: atmospheric concentration, climate response and carbon-cycle feedbacks are related but not interchangeable measures.

The current emissions trajectory remains inconsistent with a rapid approach to the Paris pathways. The Global Carbon Budget 2025 estimates that the remaining budget from January 2026 is 170 GtCO2 for 1.5°C, 525 GtCO2 for 1.7°C, and 1055 GtCO2 for 2°C, with roughly 4, 12 and 25 years respectively at current emissions levels. It projects 38.1 billion tonnes of fossil CO2 emissions in 2025, up 1.1% from 2024. These are budget estimates with uncertainty, not a countdown clock with a fixed expiry date. 1112

The Met Office's July briefing gives the OSI SAF Sea Ice Index value for June 2026 as 10.85 million km², 1.00 million km² below the 1981-2010 average and the fifth-lowest June average in the satellite record. June's average loss rate was 102,000 km² per day, close to the 1981-2010 average of 99,000 km² per day. 6

Using the same OSI SAF product, May 2026 was 12.14 million km², fourth-lowest for May and 0.92 million km² below its 1981-2010 average. The June value was therefore 1.29 million km² lower than May, a decline of about 10.6% across the month boundary. 613

C3S reports 10.9 million km², 0.6 million km² (5%) below the 1991-2020 average, and sixth-lowest June in its 48-year satellite record. Its June 2026 value was 0.1 million km² below June 2025, which ranked second-lowest in that C3S comparison. 7

The apparent rank difference, fifth-lowest versus sixth-lowest, is a methodological warning rather than a meaningful disagreement about direction. OSI SAF and C3S use related but distinct products, grids and climatological baselines. For month-to-month tracking, retain one series; for robustness, check whether independent products tell the same qualitative story. Here they do.

NASA's Earth Indicator page, updated 15 July 2026, reports 102.4 ± 4.0 mm of global mean sea-level rise since the 1993 satellite reference, with the latest measurement dated July 2026. The indicator is based on integrated multi-mission ocean-altimeter data. 4

NASA's companion indicator describes the longer rate change: 0.20 cm/year in 1993 versus 0.44 cm/year currently. Its plot tracks the satellite record since 1993 and notes that the displayed series does not include glacial isostatic adjustment. 5 The associated PO.DAAC dataset is the appropriate machine-readable source for reproducible work, with the dataset described as a weekly-to-monthly indicator series. 14

The previous June edition recorded NASA's then-current May point as 97.9 mm. The new July point is 4.5 mm higher, but that is a two-month comparison between two public snapshots, not a July-versus-June monthly change. The current rendered NASA page does not expose a clean June 2026 point or July 2025 point alongside the July 2026 value, so this edition does not invent a month-on-month or year-on-year delta. For an ESG or scientific time series, use the downloaded NASA indicator file and record its exact release date, rather than mixing dashboard snapshots.

The signal that survives the data-access caveat is the acceleration in the rate: the current annual rate is more than twice the 1993 rate. That does not mean every monthly point rises smoothly. Weather, ocean circulation, instrument processing and reference adjustments create short-term variation; the long-run rate is the more stable risk indicator.

NOAA's Climate Prediction Center issued an El Niño Advisory on 9 July 2026. It said El Niño was strengthening, with a 97% chance of persisting through early spring 2027 and an 81% chance of a very strong event in October-December 2026. The latest weekly Niño-3.4 index in that discussion was +1.2°C. 15

This is not a fifth core indicator. It is a near-term context variable that can shift the next several months of global temperature and ocean conditions. C3S also identified developing El Niño conditions in the equatorial Pacific and reported that extra-polar global sea-surface temperature reached a June record. 10

The practical reading for August is therefore two-layered: the structural indicators remain at historically stressed levels, while El Niño raises the chance that the next temperature and ocean updates will stay unusually high. That is a forecast context, not a replacement for the measured monthly series.

Reporting boundary: this article uses official information available by 5 August 2026, 10:00 UTC. The observation month differs by indicator because source datasets are released on different schedules.