Highlights
- Global temperature ranked 2 of 147 for this month of the year since 1880, +0.80 °C against 1991–2020.
- very strong El Niño: Niño 3.4 at +2.09 °C. Record value for this month of the year since 1950.
- Arctic Oscillation (AO): ranked 2 of the highest values for this month out of 77 (since 1950).
- North Atlantic (AMO): ranked 2 of the highest values for this month out of 127 (since 1900).
- Antarctic sea ice (extent): ranked 3 of the lowest values for this month out of 40 (since 1987).
- 1 geomagnetic storm day (normal 4.8, largest Kp 5.0).
- Largest earthquake: M 6.7, 74 km ENE of Tadine, New Caledonia, on 2026-09-25; 6 M ≥ 6 earthquakes in the month (normal 13).
Climate
| Indicator | Value | Gap to 1991–2020 or 12-month change | Rank for this month of the year |
|---|---|---|---|
| Global temperature (GISTEMP) | 1.38 °C | +0.80 °C | rank 2 of 147 (highest = 1, since 1880) mean of the last 12 months: 1.21 °C, rank 21 of 1750 12-month periods |
| CO₂ (Mauna Loa) | 426.1 ppm | +1.70 ppm in 12 months | record (highest of 69, since 1958) |
| Methane (global mean) last value: June 2026 | 1,942.1 ppb | +6.39 ppb in 12 months | record (highest of 43, since 1984) |
| Global mean sea level last value: June 2026 | 98.0 mm | +6.64 mm in 12 months | record (highest of 34, since 1993) |
| Arctic sea ice (extent) | 4.81 Mkm² | −0.77 Mkm² | rank 13 of 40 (lowest = 1, since 1987) |
| Antarctic sea ice (extent) | 17.32 Mkm² | −1.29 Mkm² | rank 3 of 40 (lowest = 1, since 1987) |
| Snow, Northern Hemisphere | 5.03 Mkm² | −0.48 Mkm² | rank 20 of 58 (lowest = 1, since 1967) |
For CO₂, CH₄ and sea level, which rise year after year, the twelve-month change replaces the gap to the normal; the rank compares the same month of every year.
Modes of variability
| Mode | Value | State |
|---|---|---|
| El Niño (Niño 3.4) | +2.09 °C | El Niño (very strong) |
| North Atlantic Oscillation (NAO) | +0.53 | positive |
| Arctic Oscillation (AO) | +1.16 | clearly positive |
| Southern Annular Mode (SAM) | +0.26 | near normal |
| Pacific Decadal Oscillation (PDO) | −1.55 | negative |
| North Atlantic (AMO) | +1.25 °C | clearly positive |
| Indian Ocean Dipole (IOD) | +0.65 °C | positive |
| Quasi-Biennial Oscillation (QBO) last value: February 2026 | −23.13 m/s | clearly negative |
Active links
A link is active when its driver is clearly away from its normal (El Niño beyond ±0.5 °C, Indian Ocean Dipole beyond ±0.4 °C, other modes beyond one standard deviation) and the corresponding correspondence concludes to a link. The expected direction of the effect comes from the sign of the correlation, its delay from the measured lag: a statistical tendency, not a numerical forecast.
El Niño (Niño 3.4) (+2.09, above normal) :
- El Niño and global temperature — pushes upwards, around November 2026 (lag of 2 months) (r = 0.49)
- El Niño and the CO₂ growth rate — pushes upwards, around May 2027 (lag of 8 months) (r = 0.52)
- El Niño and sea level — pushes upwards, around November 2026 (lag of 2 months) (r = 0.52)
- El Niño and length of day — pushes upwards, around October 2026 (lag of 1 months) (r = 0.45)
- El Niño, continental water and sea level — pushes downwards, around January 2027 (lag of 4 months) (r = -0.57)
- El Niño and Atlantic hurricanes — pushes downwards, over the current season (r = -0.35)
Indian Ocean Dipole (IOD) (+0.65, above normal) :
- Indian Ocean Dipole and East African rains — pushes upwards, over the current season (r = 0.55)
North Atlantic (AMO) (+1.25, above normal) :
- Atlantic oscillation and hurricanes — pushes upwards, over the current season (r = 0.44)
Drivers close to their normal: North Atlantic Oscillation (NAO), Quasi-Biennial Oscillation (QBO) (old data), Sunspots.
Sun and space
- Sunspot number: 60.3 (previous month: 76.0).
- 1 geomagnetic storm day (Kp ≥ 5); normal for this month: 4.8; largest Kp 5.0 on 2026-09-08.
- Solar flares: 0 of class X, 3 of class M. The strongest: M3.0 on 2026-09-02 (region 14524).
- Coronal mass ejections: catalogue stops on 2026-08-31, the month is not covered yet.
- Cosmic rays (Oulu monitor): 6,068 counts per minute, −231 from the normal.
Earth
- 6 earthquakes of magnitude 6 or more, 0 of 7 or more (normal: 13 per month). The largest: M 6.7, 74 km ENE of Tadine, New Caledonia, on 2026-09-25.
- 19 active tropical cyclones, the most intense: Polo (cat. 5), Lowell (cat. 5), Nolo (cat. 4), Choi-Wan (cat. 4), Surigae (cat. 4), Karina (cat. 4).
Forecasts
- October 2026: probability of a warm record for this month of the year, 68 %.
- November 2026: probability of a warm record for this month of the year, 51 %.
- December 2026: probability of a warm record for this month of the year, 72 %.
- Geomagnetic storm within three days of issue: 24 % (climatology 32 %).
- Belt electrons above the alert threshold two days ahead: 29 % (climatology 25 %).
Registered hypotheses
Bulletin frozen when issued, SHA-256 digest 70e04f7ac3048856c0a7b8f0197bbc8aac852a37d36d01318de84c0fb90f6b23, written into the sealed chain of bulletins and stamped daily with the log.
Method and sources
Values. Monthly mean of each series (daily series count only months covered at 90 %). For a series published late, the last value available, with its month. Gap to the mean of the same month over 1991–2020 (WMO normal); standard deviation of the same period for the state of the modes; rank among the same month of all available years, ties shared.
Events. Storm days: days whose largest Kp reaches 5 (GFZ), normal = share of such days for this month over 1991–2020. M and X flares of the Observatory’s catalogue, halo ejections of the CACTus catalogue, M ≥ 6 earthquakes of the USGS, active cyclones of IBTrACS; a catalogue that does not cover the end of the month yet is flagged.
Active links. For each driver outside its normal range, the correspondences where it is the cause and which conclude to a link; direction = sign of the gap × sign of r; delay = measured lag.
Issue. The bulletin of month M appears as soon as the temperature of M is published and not before the 10th of M + 1. It is never recomputed: a new issue is a new sealed entry, flagged as such.
Reading these data
A bulletin describes what is measured on its date of issue: some series are revised later, the issued bulletin is not. Active links give a probable direction, drawn from tested correlations, not a forecast: other factors can prevail in a given month. Event catalogues (coronal mass ejections, cyclones) arrive late: a “none” may only be an incomplete catalogue, flagged as such.
SOURCES OF THIS PAGE
- Arctic Oscillation index (NOAA CPC)
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NOAA CPC, monthly Arctic Oscillation index (projection of 1000 hPa height anomalies onto the leading EOF, 1950–).
· source page ↗
Licence : U.S. Government work, public domain · retrieved on Oct 23, 2026 · SHA-256 cdbee5966af8… - Antarctic Oscillation (Southern Annular Mode) monthly index (NOAA CPC)
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NOAA Climate Prediction Center, Antarctic Oscillation index: projection of the 700 hPa height anomalies poleward of 20° S on the leading EOF (base 1979–2000).
· source page ↗
Licence : U.S. Government work, public domain; cite NOAA CPC · retrieved on Oct 25, 2026 · SHA-256 95a13a252a4e… - Atlantic Multidecadal Oscillation from ERSSTv5 (NOAA NCEI)
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NOAA NCEI, ERSST v5 AMO index: monthly SST anomaly of the North Atlantic 0–60° N (Huang et al., 2017, ERSSTv5), climatology 1971–2000.
· doi:10.7289/V5T72FNM · source page ↗
Licence : U.S. Government work, public domain · retrieved on Oct 25, 2026 · SHA-256 757745a16d4a… - Global monthly mean CH₄ at the marine surface sites (NOAA GML)
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Thoning, K., Dlugokencky, E. and Lan, X. (2022). Trends in globally-averaged CH4, N2O, and SF6 determined from NOAA Global Monitoring Laboratory measurements.
· doi:10.15138/P8XG-AA10 · source page ↗
Licence : U.S. Government work, public domain; cite the NOAA GML trend data set · retrieved on Oct 25, 2026 · SHA-256 b51e4a4e6527… - Mauna Loa monthly mean CO₂ (NOAA GML)
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Lan, X., Tans, P., & Thoning, K. W. (2026). Trends in globally-averaged CO₂ determined from NOAA Global Monitoring Laboratory measurements; Mauna Loa monthly mean, after Thoning et al. (1989).
· doi:10.1029/JD094iD06p08549 · source page ↗
Licence : U.S. Government work, public domain; cite Lan, X., Tans, P. & Thoning, K. W., NOAA GML · retrieved on Oct 23, 2026 · SHA-256 d895fb5b4a59… - Indian Ocean Dipole (Dipole Mode Index) from ERSSTv5 (NOAA NCEI)
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NOAA NCEI, ERSST v5 Indian Ocean Dipole: SST anomaly difference between the western (50–70° E, 10° S–10° N) and south-eastern (90–110° E, 10° S–0°) tropical Indian Ocean (Saji et al., 1999), climatology 1971–2000.
· doi:10.7289/V5T72FNM · source page ↗
Licence : U.S. Government work, public domain · retrieved on Oct 25, 2026 · SHA-256 e1a515e8d331… - North Atlantic Oscillation index (NOAA CPC)
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NOAA CPC, monthly North Atlantic Oscillation index (rotated PCA of 500 hPa height anomalies, 1950–).
· source page ↗
Licence : U.S. Government work, public domain · retrieved on Oct 23, 2026 · SHA-256 1d4c1cdcc5d0… - Pacific Decadal Oscillation index (NCEI, ERSSTv5)
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NOAA NCEI, PDO index from ERSSTv5 (leading PC of North Pacific SST anomalies poleward of 20°N, global mean removed), 1854–.
· source page ↗
Licence : U.S. Government work, public domain · retrieved on Oct 23, 2026 · SHA-256 4fd8857f51d6… - Quasi-biennial oscillation, 30 hPa equatorial zonal wind (NOAA PSL)
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NOAA PSL climate index QBO: zonal-mean zonal wind at 30 hPa at the equator from the NCEP/NCAR reanalysis (Kalnay, E., et al., 1996, Bull. Amer. Meteor. Soc., 77, 437–471).
· doi:10.1175/1520-0477(1996)077<0437:TNYRP>2.0.CO;2 · source page ↗
Licence : U.S. Government work, public domain; cite NOAA PSL and the NCEP/NCAR reanalysis (Kalnay et al., 1996) · retrieved on Oct 25, 2026 · SHA-256 2d06ed3d14b2… - Niño 3.4 SST anomaly (NOAA PSL, ERSSTv5)
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NOAA PSL, Niño 3.4 index: monthly SST anomaly (5°N–5°S, 170°–120°W) from ERSSTv5, climatology 1991–2020.
· source page ↗
Licence : U.S. Government work, public domain · retrieved on Oct 23, 2026 · SHA-256 879cf3cb31d7… - Snow cover extent, Northern Hemisphere land, Greenland excluded (Rutgers Global Snow Lab)
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Robinson, D. A., Estilow, T. W. and NOAA CDR Program (2012). NOAA Climate Data Record (CDR) of Northern Hemisphere (NH) Snow Cover Extent (SCE), Version 1. NOAA National Climatic Data Center. Monthly areas from the Rutgers University Global Snow Lab.
· doi:10.7289/V5N014G9 · source page ↗
Licence : Free use with citation of the Rutgers Global Snow Lab and of Robinson and Estilow (2012) · retrieved on Oct 25, 2026 · SHA-256 0544c001d804… - Oulu neutron monitor, daily corrected count rate (Sodankylä Geophysical Observatory)
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Oulu neutron monitor data, cosmicrays.oulu.fi, Sodankylä Geophysical Observatory of the University of Oulu (6NM64 standard neutron monitor at 65.05° N, 25.47° E, geomagnetic cutoff rigidity ≈ 0.8 GV).
· source page ↗
Licence : Research, educational and public non-commercial use; acknowledge cosmicrays.oulu.fi and the Sodankylä Geophysical Observatory (commercial use: contact the station manager) · retrieved on Oct 26, 2026 · SHA-256 f4285114f81b… - Sea Ice Index v4, Northern Hemisphere daily extent (NSIDC)
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Fetterer, F., Knowles, K., Meier, W. N., Savoie, M., & Windnagel, A. K. (2017, updated daily). Sea Ice Index, Version 4 (G02135), Northern Hemisphere daily extent. NSIDC.
· doi:10.7265/N5K072F8 · source page ↗
Licence : NSIDC data, free with citation (Fetterer et al., 2017, updated daily) · retrieved on Oct 23, 2026 · SHA-256 d36fc1791ba9… - Sea Ice Index v4, Southern Hemisphere daily extent (NSIDC)
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Fetterer, F., Knowles, K., Meier, W. N., Savoie, M., & Windnagel, A. K. (2017, updated daily). Sea Ice Index, Version 4 (G02135), Southern Hemisphere daily extent. NSIDC.
· doi:10.7265/N5K072F8 · source page ↗
Licence : NSIDC data, free with citation (Fetterer et al., 2017, updated daily) · retrieved on Oct 23, 2026 · SHA-256 824c6aff3c2e… - Global mean sea level by satellite altimetry (University of Colorado Sea Level Research Group)
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University of Colorado Sea Level Research Group, global mean sea level release 2026_rel2 (TOPEX/Poseidon, Jason-1/2/3, Sentinel-6MF), seasonal signals removed, glacial isostatic adjustment applied; Nerem, R. S., et al. (2010), Marine Geodesy 33, 435; Nerem, R. S., et al. (2018), PNAS 115, 2022–2025.
· doi:10.1073/pnas.1717312115 · source page ↗
Licence : Freely available for research and education; cite the CU Sea Level Research Group and Nerem et al. (2010, 2018) · retrieved on Oct 25, 2026 · SHA-256 eef45eb6580a… - SILSO monthly mean total sunspot number V2.0
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SILSO World Data Center. The International Sunspot Number, V2.0. Royal Observatory of Belgium, Brussels.
· source page ↗
Licence : CC BY-NC 4.0 · retrieved on Oct 23, 2026 · SHA-256 4749cc16c68e… - GISTEMP v4 global land-ocean temperature anomaly
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GISTEMP Team (2026). GISS Surface Temperature Analysis (GISTEMP), version 4. NASA Goddard Institute for Space Studies; Lenssen et al. (2024).
· doi:10.1029/2023JD040179 · source page ↗
Licence : NASA data, public domain; cite GISTEMP Team and Lenssen et al. (2024) · retrieved on Oct 23, 2026 · SHA-256 4c64eda288bc… - Geomagnetic Kp and ap indices (GFZ Helmholtz Centre for Geosciences)
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Matzka, J., Stolle, C., Yamazaki, Y., Bronkalla, O. and Morschhauser, A. (2021). The geomagnetic Kp index and derived indices of geomagnetic activity. Space Weather, 19, e2020SW002641. Data: Matzka, J., Bronkalla, O., Tornow, K., Elger, K. and Stolle, C. (2021). Geomagnetic Kp index. V. 1.0. GFZ Data Services.
· doi:10.5880/Kp.0001 · source page ↗
Licence : CC BY 4.0; cite Matzka et al. (2021) · retrieved on Oct 26, 2026 · SHA-256 d537f7d9e8ae… - USGS ComCat earthquakes M ≥ 4.5 (FDSN event service)
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U.S. Geological Survey, Earthquake Hazards Program (2017). Advanced National Seismic System (ANSS) Comprehensive Catalog of Earthquake Events and Products. Accessed through the FDSN event web service.
· doi:10.5066/F7MS3QZH · source page ↗
Licence : U.S. Government work, public domain; cite USGS ANSS ComCat · retrieved on Oct 26, 2026 · SHA-256 54eb2b59eac4…