Global Climate – September 2026 Update

Laki (Skaftá Fires) eruption

An eight-month fissure eruption in Iceland that put more sulphur dioxide into the air than any other eruption in the historical record. A 'dry fog' spread across Europe, the Northern Hemisphere winter of 1783-84 ran about 1.5°C colder than normal, and the summer of 1784 was cold too.

Zambri et al. 2019

Tambora eruption

The largest eruption in recorded history. It cooled the Northern Hemisphere by about 0.5°C and produced 1816's 'Year Without a Summer', with crops failing widely across Europe and North America.

Smithsonian Global Volcanism Program

Krakatau eruption

The eruption destroyed most of the island, and the tsunamis it set off killed more than 36,000 people. It cooled the Northern Hemisphere by about 0.3°C over 1884-86.

Smithsonian Global Volcanism Program

Santa María eruption

One of three large eruptions in 1902, alongside Mont Pelée and Soufrière St Vincent. Together they slightly cooled the Northern Hemisphere in 1902-03.

Smithsonian Global Volcanism Program

Novarupta (Katmai) eruption

The largest volcanic eruption anywhere in the world in the 20th century - 13 km3 of magma, about thirty times the 1980 Mount St. Helens eruption - at Novarupta in Alaska on 6-8 June 1912. Ash reached 100,000 ft and cooled the Northern Hemisphere by roughly 0.3°C over 1912-13. Unlike a tropical eruption such as Pinatubo, a high-latitude eruption's haze stays in its own hemisphere, so it did little to the Southern Hemisphere.

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

The 1955-56 La Niña

One of the strongest La Niñas since instrument-based ENSO records begin in 1950, and part of a run of cool Pacific years through the mid-1950s. La Niña cools global temperatures slightly for a year or two while it lasts, and shifts rainfall patterns worldwide.

ONI -1.6°C · RONI -1.4°C

NOAA CPCENSO Tracker

Keeling Curve begins

Charles David Keeling begins continuous measurements of atmospheric CO₂ at Mauna Loa Observatory in Hawaii, starting at about 315 ppm. The record has risen every year since and is now the longest unbroken direct measurement of CO₂ anywhere - the 'Keeling Curve'.

NOAA GMLGreenhouse Gases

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

West African Sahel drought begins

The West African Sahel drought begins abruptly (1969-70), rainfall dropping by up to 40%, severe enough to register in global land-precipitation records.

Learn more →Extreme Weather

US Clean Air Act

Major US federal legislation setting strict limits on sulphur dioxide and particulate pollution. It began a long fall in US sulphate emissions, and with it the removal of a haze that had been masking part of the underlying greenhouse warming.

US EPA

The 1972-73 El Niño

One of the strongest El Niños on record. It contributed to failed grain harvests in the Soviet Union and elsewhere in 1972, and to a sharp rise in world food prices - an early sign of how far ENSO's reach extends.

ONI +1.8°C · RONI +2.0°C

NOAA CPCENSO Tracker

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

The 1975-76 La Niña

A strong, distinct La Niña following closely on the 1973-74 event, together forming one of the most sustained cool-phase periods in the ENSO record.

ONI -1.6°C · RONI -1.1°C

NOAA CPCENSO Tracker

Pacific Decadal Oscillation flips to a warm phase

The Pacific Decadal Oscillation - a slow natural cycle in North Pacific sea temperatures - switches from its cool to its warm phase in 1976-77. The change was abrupt enough to be called the 1976-77 Pacific Climate Shift: it warmed Alaska and the west coast of North America, and reorganised North Pacific fisheries.

Learn more →

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

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

The strongest El Niño since 1950 on NOAA's Relative Oceanic Niño Index, which strips out the background warming of the tropical oceans before ranking events. On the older index that leaves that warming in, 2015-16 comes out on top instead.

ONI +2.1°C · RONI +2.4°C

NOAA CPC, NOAA CPC (2)ENSO Tracker

The Antarctic ozone hole is discovered

British Antarctic Survey scientists Joe Farman, Brian Gardiner and Jon Shanklin publish their Halley and Faraday measurements on 16 May 1985, showing October ozone over Antarctica had fallen to about two-thirds of earlier decades. The cause is traced to chlorofluorocarbons, and the finding triggers the fastest international environmental response on record.

Nature, UKRI

The Montreal Protocol

Signed in 1987 to phase out ozone-depleting chlorofluorocarbons, the Montreal Protocol turned out to be one of the most consequential climate treaties ever agreed. CFCs are potent greenhouse gases in their own right, and NOAA estimates the Protocol prevented up to 2°C of warming by 2100 - around 1°C from the emissions avoided, and up to 1°C more by sparing forests and other carbon sinks from increased ultraviolet radiation.

NOAA, Wikipedia

CO₂ crosses 350 ppm

Atmospheric CO₂ passes 350 ppm. In the same year James Hansen told a US Senate committee that global warming was already detectable, the moment it entered mainstream politics. Twenty years later, in 2008, Hansen proposed 350 ppm as the safe upper limit - a level the world had already left behind.

NOAA GMLGreenhouse Gases

The 1988-89 La Niña

One of the strongest La Niñas on record, arriving straight after the 1986-87 El Niño - a swing from one extreme of the Pacific cycle to the other in barely a year.

ONI -1.9°C · RONI -1.9°C

NOAA CPCENSO 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

Mount Pinatubo in the Philippines erupts in June 1991, the largest eruption since 1912. Its sulphate haze cooled global surface temperature by about 0.5°C in 1992 and reduced rainfall over land for about two years, before the warming trend resumed.

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Atlantic Multidecadal Oscillation flips to a warm phase

The Atlantic Multidecadal Oscillation - a slow natural cycle in North Atlantic sea temperatures, roughly 60-70 years long - flips to its warm phase in 1995. Warm phases are linked to more active Atlantic hurricane seasons, wetter summers in parts of north-west Europe and more frequent drought in the central and western United States.

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1997-98 El Niño

One of the strongest El Niños on record, and the one the textbook El Niño pattern is usually drawn from. It pushed 1998 to what was then the warmest year ever measured, and set off the first global-scale coral bleaching event.

ONI +2.4°C · RONI +2.3°C

NOAA CPC, NOAA NCEIENSO Tracker

First global mass coral bleaching event

The first recorded global-scale coral bleaching event, during the strong 1997-98 El Niño (peak ONI +2.3) followed by a strong La Niña that brought further warm-water stress to the Pacific.

NOAA Coral Reef WatchENSO Tracker

Escalating severity of global coral bleaching events

Each of the four global mass coral-bleaching events since 1998 has been more widespread and severe than the last - from a regional-scale first event to 84% of the world's reef area affected by 2023-25 - tracking the same warming trend as rising ocean heat content, independent of any single El Niño's strength.

NOAA Coral Reef Watch / NESDISENSO Tracker

The 1999-2001 La Niña

A strong La Niña that ran for three winters after the record 1997-98 El Niño, peaking at an ONI of -1.53. It pulled global temperatures back below 1998's record for several years, and brought the usual La Niña pattern of dry winters across the southern United States and wet years in Australia and Indonesia.

ONI -1.5°C · RONI -1.6°C

NOAA CPC ONI

Pacific Decadal Oscillation flips back to a cool phase

The Pacific Decadal Oscillation - a slow natural cycle in North Pacific sea temperatures - flips back to its cool phase around 1998-99. The cool phase that followed is one reason global surface warming appeared to slow in the 2000s, as more heat went into the deep Pacific.

Learn more →

The 2007-08 La Niña

A strong La Niña linked to reduced Atlantic hurricane wind shear and drought conditions across the southern US and East Africa.

ONI -1.8°C · RONI -1.7°C

NOAA CPCENSO Tracker

2009-10 El Niño

A moderate-to-strong El Niño that peaked around the turn of 2009-10. It helped make 2010 one of the warmest years on record at the time, and was followed straight away by the strong La Niña of 2010-12.

ONI +1.5°C · RONI +1.5°C

NOAA/IRI ENSO archiveENSO Tracker

Second global mass coral bleaching event

The second global-scale coral bleaching event, in 2010, when a moderate-to-strong El Niño pushed tropical sea temperatures above the level corals can tolerate across the Indian Ocean, South-East Asia and the Caribbean.

NOAA Coral Reef WatchENSO Tracker

Global heatwave days sharply accelerate

Globally, heatwave days have roughly doubled each decade since 2010 - from an average of 5.3 a year in the 2000s to 11.5 in the 2010s and 18.9 so far in the 2020s, weighted by land area across 169 countries. El Niño has not become more extreme. The whole temperature distribution has shifted upwards, so the same natural El Niño and La Niña cycle now pushes far more days over fixed extreme-heat thresholds.

Learn more →Heatwave Days

The 2010-2012 La Niña

A strong double-winter La Niña peaking at an ONI of -1.57. It gave Australia its wettest two years on record and the Queensland floods of 2010-11 - so much rain fell on land that global sea level briefly dropped in 2011 - and it fed drought in the Horn of Africa and in Texas.

ONI -1.6°C · RONI -1.6°C

NOAA CPC ONI

Arctic sea ice record minimum, 2012

Arctic sea ice shrinks to 3.41 million km² in September 2012, the smallest extent of the satellite era, which began in 1979. No year since has gone lower; 2020, at 3.74 million km², came closest.

NSIDC / NOAA Climate.gov

CO₂ crosses 400 ppm

Atmospheric CO₂ passes 400 ppm at Mauna Loa on 9 May 2013 - a level the planet had not seen for 3-5 million years, since the Pliocene, when sea levels were many metres higher.

NOAA GMLGreenhouse Gases

Third global mass coral bleaching event

The third and (at the time) most severe global bleaching event, spanning 2014-2017 and peaking during the record 2015-16 El Niño - 68.2% of the world's reef area experienced bleaching-level heat stress.

NOAA / AGUENSO Tracker

2015-16 El Niño

The strongest El Niño on record by raw ONI - though on NOAA's newer RONI index, which strips out background tropical-ocean warming, 1982-83 ranks slightly ahead instead. 2016 became the hottest year on record at that time (+1.0°C above pre-industrial).

ONI +2.6°C · RONI +2.3°C

NOAA CPCENSO Tracker

2015-2025: the eleven warmest years on record

The eleven warmest years ever measured are 2015 through 2025, an unbroken run - the longest sustained stretch of record warmth in the 176-year instrumental record. 2023 and 2024 each broke the previous record in turn.

Learn more →

COVID-19 lockdowns - CO₂ emissions dip

Global fossil CO₂ emissions fell about 5.8% in 2020, from 37.0 to 34.8 billion tonnes, yet atmospheric CO₂ still rose 2.5 ppm - the dip barely registers in the atmospheric record. Emissions were back to pre-pandemic levels by 2022.

Le Quéré et al. 2020

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

The 2020-2023 'triple-dip' La Niña

Three consecutive La Niña winters - a 'triple dip', which has happened only a handful of times since 1950 - peaking at an ONI of -1.11. It held global temperatures slightly below where the warming trend would otherwise have put them, and coincided with five failed rainy seasons in a row in the Horn of Africa and severe flooding in eastern Australia in 2022.

ONI -1.1°C · RONI -1.5°C

WMO, WMO (2)ENSO Tracker

Hunga Tonga-Hunga Ha'apai eruption

An underwater eruption in Tonga that put very little sulphur dioxide into the stratosphere but a record amount of water vapour - about 150 million tonnes. Water vapour traps heat, so it was first expected to warm the planet, but later studies found the small sulphate haze outweighed it: the net effect was a slight cooling of the Southern Hemisphere, around 0.1°C, in 2022-23.

Proud et al. 2022

Fourth global mass coral bleaching event

The fourth and most severe global bleaching event on record - bleaching-level heat stress impacted 84% of the world's coral reef area across the Pacific, Atlantic and Indian Oceans, confirmed by NOAA 15 April 2024.

NOAA NESDISENSO Tracker

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

Ocean acidification crosses its planetary boundary

As of 2025, ocean acidification has crossed its planetary boundary for the first time, making it the seventh of the nine boundaries to be breached. The oceans absorb about a quarter of the CO₂ we emit, which makes seawater more acidic and harder for corals and shell-forming sea life to build with.

Findlay et al. 2025