Alaska Climate – Sep 2026September 2026 Update

Novarupta (Katmai) eruption

This happened in Alaska. Novarupta erupted on 6-8 June 1912 on the Alaska Peninsula - the largest volcanic eruption anywhere in the world in the 20th century, about thirty times the size of Mount St. Helens in 1980. The summit of Mount Katmai, six miles away, collapsed as magma drained out beneath it. Kodiak Island, downwind, was in darkness for nearly three days. The ash flow buried a valley so deep that steam vented through it for years afterwards, giving the Valley of Ten Thousand Smokes its name.

Smithsonian Global Volcanism Program, Alaska Volcano Observatory, National Park Service, Oman et al. 2005

Post-WWII industrial expansion begins

After the Second World War, coal and oil use grew rapidly across Europe, North America and the Soviet Union. Global sulphur dioxide emissions rose from about 30 to about 130 million tonnes a year by 1980, and the sulphate haze they formed masked part of the greenhouse warming underneath - the effect known as 'global dimming'.

Klimont et al. 2013

1956: Alaska's coldest year

1956 is Alaska's coldest year on record, 2.2°C below its 1961-90 average. It fell during the cool phase of the Pacific Decadal Oscillation, which kept Alaskan winters colder until the 1976-77 flip; no year since has been as cold.

National Park Service, Alaska Climate Research Center

Agung eruption

Agung's eruption in Bali put a veil of sulphate haze into the stratosphere that cooled global temperature by about 0.3°C over 1963-66.

Smithsonian Global Volcanism Program, NOAA Global Monitoring Laboratory

US Clean Air Act

The 1970 Clean Air Act set strict national standards for sulphur dioxide and particulates, and American skies got measurably cleaner over the decades that followed. There is a climate sting in that success: sulphate aerosols reflect sunlight, so removing them removed a cooling effect that had been partly masking greenhouse warming. Measured here, Alaska averaged +1.67°C warmer across 2006-2025 than across the two decades before the Act, 1951-1970 - the largest rise of any state with a record going back that far. Cleaning the air was unambiguously right for human health. It also revealed how much warming had already been bought and paid for, and nowhere shows that more starkly than Alaska.

US EPA

The 1973-74 La Niña

The strongest La Niña of the 1950-present record, part of a multi-year cool phase that also included a second, separate La Niña in 1975-76.

ONI -2.0°C · RONI -1.9°C

NOAA CPCENSO Tracker

Pacific Decadal Oscillation flips to a warm phase

The 1976-77 Pacific Decadal Oscillation flip matters more to Alaska than almost anywhere. The warm phase that began then brought warmer coastal waters and milder winters, and is associated with a marked reorganisation of North Pacific and Bering Sea ecosystems, salmon runs among them.

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Global SO2 emissions peak

Global sulphur dioxide emissions peak at about 130 million tonnes a year, then begin a long decline as Europe, North America and Japan clean up their air. As the aerosol mask thins, the rate of global warming picks up through the 1980s.

Klimont et al. 2013

Alaska's amplified Arctic warming

Alaska warms roughly 2-3x the global average rate; the wider Arctic has warmed nearly 4x faster than the globe since 1979 (peer-reviewed, Communications Earth & Environment 2022) - driven by sea-ice loss exposing darker, heat-absorbing ocean.

Communications Earth & Environment, 2022

El Chichón eruption

A sulphur-rich eruption in Mexico whose aerosol cloud stayed in the stratosphere for more than two years, cooling the Northern Hemisphere by about 0.2°C.

Smithsonian Global Volcanism Program

1982-83 El Niño

Alaska's link to the tropical Pacific runs mainly through temperature rather than rainfall: this site's own regression of winter temperature on the ONI index gives Alaska the strongest positive coefficient of any state, so El Niño winters here tend to run mild. The rainfall signal is weak.

ONI +2.1°C · RONI +2.4°C

NOAA CPC, NOAA CPC (2)ENSO Tracker

Daytime warming catches up with the night-led pattern

Across 1961-90, 81% of the world's land saw nights warming faster than days. Across 1991-2020 the pattern reversed: 70% saw days warming faster, as the industrial haze that had been dimming daytime sunshine was cleaned up. The study compares two fixed thirty-year windows; measured as a turning point, this site's own global series turns around 1982.

Zhong et al. 2023

Mount Pinatubo erupts

Pinatubo's cooling does not show in Alaska's own record. 1993, two years after the June 1991 eruption, was warmer than most years there - the 7th-warmest of 76 - because local weather that year outweighed the eruption's global cooling. A single large eruption can hold temperatures down for two or three years; it cannot reverse the trend.

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Atlantic Multidecadal Oscillation flips to a warm phase

This is an Atlantic cycle, and its direct relevance to Alaska is limited. The Pacific Decadal Oscillation is the ocean rhythm that matters most to Alaskan winters, along with the Bering Sea ice record.

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1997-98 El Niño

Alaska's link to the tropical Pacific runs mainly through temperature rather than rainfall: this site's own regression of winter temperature on the ONI index gives Alaska the strongest positive coefficient of any state, so El Niño winters here tend to run mild. The rainfall signal is weak.

ONI +2.4°C · RONI +2.3°C

NOAA CPC, NOAA NCEIENSO Tracker

Pacific Decadal Oscillation flips back to a cool phase

The Pacific Decadal Oscillation returned to a cool phase around 1998-99, shifting North Pacific temperature patterns that bear directly on Alaskan coastal waters and fisheries.

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Start of the sustained rise in US heatwave frequency

Alaska's own Heatwave Days (WSDI) count rose from a 1961-90 average of 9.6 days a year to 19.2 in 2016-25 - a clear rise, though more moderate than the 2.4x averaged across the 50 states.

World Bank CCKP (CCKP), NOAA Climate at a Glance

Post-2013 acceleration in US temperatures

7 of Alaska's ten warmest years on record have occurred since 2013, and 9 of the ten since 2000, with 2019 the warmest of all.

NOAA Climate at a Glance

2015-16 El Niño

Alaska's link to the tropical Pacific runs mainly through temperature rather than rainfall: this site's own regression of winter temperature on the ONI index gives Alaska the strongest positive coefficient of any state, so El Niño winters here tend to run mild. The rainfall signal is weak.

ONI +2.6°C · RONI +2.3°C

NOAA CPCENSO Tracker

2015-2025: the eleven warmest years on record

Globally, the eleven warmest years on record have all happened since 2015. Alaska's own record is a looser fit - six of its eleven warmest fall in that span, with 2014, 2004, 2002, 1993 and 1981 outside it. Its warmest year is 2019.

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Record-low Bering Sea ice, 2018 & 2019

Winter 2018 Bering Sea ice hit its lowest level in a record dating to 1850 (~10% of normal); NOAA scientists called it 'unprecedented' and said models didn't expect this for 10-15 more years. 2019 nearly repeated it.

NOAA

Alaska's warmest year on record, 2019

2019 was Alaska's warmest year in the record, 6.2°F above its long-term average and 0.3°F above the previous record set only three years earlier in 2016. Utqiagvik, Kotzebue, King Salmon, Fairbanks, Bethel, Anchorage, Northway, McGrath, Kodiak and Cold Bay all set their own warmest-year records. On 4 July Anchorage reached 90°F for the first time ever measured, beating its all-time high by 5°F.

NOAA Climate.gov, NOAA NCEI, NOAA Arctic Report Card 2019

Low-sulphur shipping fuel rule (IMO 2020)

New international shipping rules cut the sulphur allowed in ship fuel from 3.5% to 0.5% almost overnight, removing about 8 million tonnes of sulphur dioxide a year. With less sulphate haze over the oceans, it may have added around 0.1°C of warming by 2023-24.

Gettelman et al. 2024

2023-24 El Niño

A strong El Niño arriving on top of long-term greenhouse warming, with the cut in shipping sulphur from the 2020 fuel rule adding a little more. Together they produced the record global temperatures of 2023 and 2024.

ONI +2.0°C · RONI +1.4°C

NOAA CPCENSO Tracker