Weekly Global Climate Pulse

By Paul Harrison | Founder & Publisher, Orbis Weather

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Thursday, October 29, 2026

Weekly Global Climate Pulse: Thursday, October 29, 2026

By Paul Harrison, Orbis Weather

At a glance

El Niño kept strengthening this week, with a record weekly reading on the Australian Bureau of Meteorology’s Niño 3.4 index, while WMO reported record greenhouse gas levels for 2025.

Data dates: NOAA CPC weekly ENSO update, October 26; BoM climate driver update, October 27; WMO Greenhouse Gas Bulletin, October 27; NOAA CPC monthly ENSO discussion, October 8; Copernicus September bulletin, October 9–14; NOAA NCEI September report, October 9; NSIDC sea ice analysis, October 7; US Drought Monitor, map valid October 20.

  • ENSO: weekly Niño 3.4 anomaly +2.5°C (+4.5°F) (NOAA CPC, October 26); El Niño Advisory in force.
  • Oceans: September sea surface temperature 60°S–60°N of 21.05°C (69.89°F), a September record (Copernicus).
  • Temperatures: September 2026 was +1.63°C (+2.93°F) above 1850–1900, second warmest September (Copernicus).
  • Sea ice: Antarctic daily extent at record lows from October 2 (NSIDC, October 7).
  • Drought: 50.67% of the contiguous US in drought, down from 53.73% a week earlier (US Drought Monitor, October 20).
  • Records: carbon dioxide averaged a record 426.8 ppm in 2025 (WMO, October 27).

El Niño and La Niña

A strong El Niño is in place and still strengthening, and every major agency expects it to last into early 2027. NOAA’s Climate Prediction Center (CPC) keeps an El Niño Advisory in force. Its October 8 discussion says a “strong-to-very strong El Niño” is likely through January–March 2027, with a greater than 83% chance.

Measure

Value

Agency

Date

Weekly Niño 3.4 anomaly

+2.5°C (+4.5°F)

NOAA CPC

Weekly update, Oct 26

Weekly relative Niño 3.4

+2.88°C (+5.2°F), a weekly record

Australian Bureau of Meteorology (BoM)

Week ending Oct 25

Relative ONI (RONI), Jul–Sep

+1.7°C (+3.1°F)

NOAA CPC

Oct 26

Chance of a “historic” event (3-month RONI of +2.5°C [+4.5°F] or more)

54% Sep–Nov, 83% Oct–Dec, 70% Nov–Jan

NOAA CPC

Oct 8

The agencies use different indices, so their numbers are not directly comparable. The Japan Meteorological Agency (JMA) said on October 9 that the September NINO.3 anomaly of +4.0°C (+7.2°F) beat the December 1997 record. BoM said on October 27 that its longer monthly record still stands. The World Meteorological Organization (WMO) update of October 21 puts Niño 3.4 at about +3.8°C (+6.8°F) for November–January.

Indian Ocean Dipole: BoM says a positive event is under way. Its index was +0.69°C (+1.24°F) in the week ending October 25, the seventh straight week above the +0.4°C (+0.72°F) threshold. WMO expects the event to decline toward neutral over November–January.

Oceans and global temperatures

The world’s oceans set new records in September, and the month was the second warmest September on record for air temperature. These are the latest monthly figures; no new global monthly data were released this week.

Sea surface temperature. Copernicus (C3S) put the average for 60°S–60°N at 21.05°C (69.89°F), the highest for any September. NOAA’s National Centers for Environmental Information (NCEI) reported an ocean surface anomaly of +1.10°C (+1.98°F) against the 20th-century average, the highest for any month on record. C3S also measured a record monthly Niño 3.4 anomaly of +2.99°C (+5.38°F).

Marine heatwaves and coral. NOAA’s Physical Sciences Laboratory found 42% of the global ocean in a marine heatwave in September, the highest share of any month since 1991. NOAA Coral Reef Watch still lists the Fourth Global Coral Bleaching Event as current (page updated October 8).

Air temperature. C3S and NCEI both rank September 2026 second, behind September 2023.

Month (2026)

vs 1991–2020

vs 1850–1900

Rank (C3S)

September

+0.82°C (+1.48°F)

+1.63°C (+2.93°F)

2nd-warmest September

August

+0.85°C (+1.53°F)

+1.65°C (+2.97°F)

Warmest August

July

+0.67°C (+1.21°F)

+1.47°C (+2.65°F)

Joint 2nd-warmest July

June

+0.56°C (+1.01°F)

+1.39°C (+2.50°F)

2nd-warmest June

May

+0.55°C (+0.99°F)

+1.42°C (+2.56°F)

2nd-warmest May

Source: C3S monthly surface air temperature bulletins (ERA5).

C3S said the 12 months to September averaged 1.50°C (2.70°F) above pre-industrial, and January–September ranks second behind 2024. NCEI put September at +1.33°C (+2.39°F) above the 20th-century average and called a top-five year for 2026 “very likely”.

Sea ice

Antarctic sea ice is the standout: the US National Snow and Ice Data Center (NSIDC) reported record-low daily extents from October 2 onward. The Arctic summer minimum was low but not extreme. NSIDC’s latest analysis is dated October 7, so these are not new this week.

Hemisphere

Seasonal turning point (NSIDC)

September average (NSIDC)

Latest status

Arctic

Minimum 4.60 million km² (1.78 million sq mi) on Sep 12; tied 10th lowest in the satellite record; 1.62 million km² (0.63 million sq mi) below the 1981–2010 average minimum

4.81 million km² (1.86 million sq mi), 13th lowest

Early October: below average along the Eurasian coast, especially the Kara and Barents Seas

Antarctic

Maximum likely 17.59 million km² (6.79 million sq mi) on Sep 14; third lowest

17.32 million km² (6.69 million sq mi)

Record-low daily extents from Oct 2; “close to the record low for the date set in 2023” on Oct 6

NSIDC called its Arctic minimum figure preliminary on September 23; its October 7 analysis confirmed the dates and ranks. Copernicus, using a different dataset and the 1991–2020 baseline, ranks September Arctic extent 16th lowest and Antarctic extent third lowest.

Drought

Drought in the contiguous US eased for a third straight week, but about half the lower 48 states remain in drought. The figures below are from the US Drought Monitor map valid October 20 and released October 22. This week’s map, valid October 27, is due later today.

Map date

Area in drought (D1–D4)

Extreme or exceptional (D3–D4)

Abnormally dry or worse (D0–D4)

Oct 20

50.67%

9.37%

73.18%

Oct 13

53.73%

9.79%

74.54%

Sep 29

59.38%

11.53%

78.36%

Storms on October 13–15 brought widespread improvement to Texas and Oklahoma. Drought worsened from the Lower Mississippi Valley into the western Ohio Valley, with exceptional drought (D4) developing or expanding in southern Arkansas and northern Louisiana. Drought.gov counted 92.6 million people in drought as of October 20.

Worldwide. FEWS NET’s October 6 special report named East Africa and Southern Africa as the regions of highest concern for El Niño impacts. It said South Sudan and Karamoja, Uganda, were on track for their driest year on record. The ASEAN Specialised Meteorological Centre’s October–December outlook gives a high chance of below-normal rain over much of the Maritime Continent. In India, NewsMeter reported on October 28 that Telangana had declared drought in 111 mandals after monsoon rainfall came in 17% below normal.

Records and milestones

The week’s new milestone is WMO’s Greenhouse Gas Bulletin, which reported record levels of all three main greenhouse gases in 2025.

Gas (2025 global average)

Level

Share of pre-industrial

Carbon dioxide

426.8 ppm

153%

Methane

1,948 ppb

267%

Nitrous oxide

339.1 ppb

126%

Source: WMO Greenhouse Gas Bulletin No. 22, released October 27.

AFP reported that carbon dioxide rose 2.8 ppm from 2024 to 2025, a smaller rise than the 3.6 ppm a year earlier.

What to watch

The next two weeks bring updated El Niño outlooks from Japan and the US, and the UN climate conference.

Date

Release or event

What it will show

Nov 9–20

COP31 climate conference, Antalya, Türkiye

International climate negotiations

Tue, Nov 10

JMA El Niño outlook

Whether the record NINO.3 warmth continues

Thu, Nov 12

NOAA CPC ENSO diagnostic discussion

October Niño values and updated probabilities of a historic event

Thu, Nov 19

NOAA CPC monthly and seasonal outlooks

US temperature and precipitation outlooks

Early to mid November (no date announced)

Copernicus and NOAA NCEI October reports

Whether ocean temperature records continued in October

About this report

The Weekly Global Climate Pulse tracks slow-moving climate indicators, not day-to-day weather. Many of them update monthly, so each figure carries its issue date. Agencies compare against different baselines. The 1991–2020 average describes the recent climate, 1850–1900 stands in for pre-industrial conditions, and NSIDC uses 1981–2010 for sea ice. An anomaly against an older baseline is larger, so figures on different baselines should not be compared directly. Recent figures, especially sea ice, can be revised.

Glossary

  • Anomaly: the difference between a measured value and the long-term average for that place and time.
  • Niño 3.4: a patch of the central equatorial Pacific whose sea surface temperature is the main gauge of El Niño and La Niña.
  • Relative ONI (RONI): NOAA’s three-month Niño 3.4 index, measured relative to the tropics as a whole.
  • Indian Ocean Dipole: the temperature difference between the western and eastern Indian Ocean, which affects rainfall around the basin.
  • Sea ice extent: the total ocean area where ice covers at least a set minimum share of the surface.

Frequently asked questions

Is this El Niño the strongest on record? It depends on the index. JMA says its September NINO.3 value broke the 1997 record, and BoM’s weekly index hit a record. NOAA rates a “historic” three-month event as likely but not yet certain, and BoM says its monthly record still stands.

When will El Niño peak and end? BoM and WMO expect a peak around November or December. NOAA CPC expects El Niño to last through March–May 2027, with neutral conditions favoured from April–June 2027.

Was September the hottest month on record? No. Copernicus and NOAA both rank it the second warmest September, behind 2023. The ocean surface, however, was the warmest on record for September in both datasets.

Is US drought getting better? Overall, yes, for now. The share of the lower 48 in drought fell by almost nine percentage points between late September and October 20, though the Lower Mississippi Valley got drier.

Sources

Sources & Methodology
Weekly Global Weather Watch is compiled by Orbis Weather using information from official national and international meteorological agencies, including NOAA, the National Weather Service, National Hurricane Center, Weather Prediction Center, Climate Prediction Center, World Meteorological Organization and relevant national weather agencies worldwide.

Orbis Weather reviews these official observations, forecasts, warnings and outlooks to identify the most significant global weather patterns and hazards for the week ahead. Forecast conditions can change as new observations and model guidance become available.

About the Author

Paul Harrison — Founder & Publisher, Orbis Weather

Paul Harrison founded Orbis Weather in 2026 to make global weather and natural-hazard information easier to find, follow and understand. His coverage includes tropical cyclones, severe weather, extreme temperatures, earthquakes, volcanoes, wildfires, flooding and significant natural disasters worldwide.

View all articles by Paul Harrison → | Editorial Standards →

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