Why Anak Krakatau’s eruption is unlikely to cool the planet
The eruption may briefly lower temperatures nearby, but it is not expected to offset warming from a rapidly strengthening El Niño.
Indonesia’s Anak Krakatau volcano sent a towering plume of ash and gas into the atmosphere last week, disrupted thousands of flights and raised questions about whether the eruption could temporarily cool the planet.
Despite the dramatic appearance of Krakatau, often referred to as Krakatoa, current evidence indicates it is unlikely to have a meaningful effect on global temperatures or counteract the significant warming expected from the quickly unfolding El Niño.
“The ash plume from Krakatau has remained primarily in the troposphere and does not appear to have reached the stratosphere,” AccuWeather Senior Director of Forecasting Operations Dan DePodwin said. “As a result, the eruption could produce short-term, localized effects on temperatures, but a meaningful impact on global temperatures is unlikely.”
Anak Krakatau erupts ash and volcanic gases in this image acquired with the OLI (Operational Land Imager) on Landsat 8 on September 5, 2026. (Image: NASA Earth Observatory/Michala Garrison)
Satellite images captured the explosive activity on Saturday, Sept. 5, as a white plume of volcanic gas rose above a sprawling brown cloud of ash. Indonesia’s meteorological agency reported volcanic material at altitudes of up to 50,000 feet west of the volcano and 20,000 feet to its east, according to NASA’s Earth Observatory.
The higher plume remained below the tropical tropopause, the boundary between the troposphere and stratosphere. That boundary is generally higher near the equator than at the poles.
Why some eruptions cool the planet
An eruption must inject a large amount of sulfur dioxide high into the stratosphere to cause significant global cooling. There, the gas can form tiny sulfate aerosols that reflect some incoming sunlight back into space.
Ash itself is made of small, jagged pieces of rock and glass. Most ash in the troposphere is dispersed by winds or removed by rain relatively quickly. Even ash near 30,000 feet, where many commercial aircraft fly, typically does not remain in the atmosphere long enough to substantially affect the global climate.
The stratosphere is different. Because it is more stable and largely above the weather systems that cleanse the lower atmosphere, sulfate aerosols can remain aloft for years and spread around the globe.
That happened after Mount Pinatubo erupted in the Philippines in 1991. The enormous eruption released an estimated 20 million tons of sulfur dioxide and ash more than 12 miles into the atmosphere. The resulting aerosol cloud spread around the world and reduced the amount of solar energy reaching Earth’s surface, according to NASA.
File photo: A Philippine flag flies over the gate to U.S.-run Clark Air Force Base in Angeles City, Philippines, Wednesday, June 12, 1991, as a cloud of volcanic ash from the erupting Mount Pinatubo looms in the distance. (AP Photo/Danny Perez)
“Anak Krakatau’s eruption is not comparable in scale to Mount Pinatubo,” DePodwin said. “Pinatubo lofted a tremendous amount of volcanic material well into the stratosphere, allowing it to remain in the atmosphere and produce a small but measurable cooling effect.”
An even larger eruption occurred at Mount Tambora in Indonesia in 1815. Its global climate effects contributed to 1816 becoming known as the “Year Without a Summer,” when unusually cold and wet conditions led to widespread crop failures across parts of Europe and North America.
No comparable impact is expected from the latest Anak Krakatau eruption.
Eruptions continue, but activity has declined
Plumes of ash and volcanic gases from Anak Krakatau drift over Indonesia and the Indian Ocean in this image captured by the VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite on Sept. 5, 2026. (Image: NASA Earth Observatory/Michala Garrison
Anak Krakatau’s continuous eruptive episode began late Sept. 4 and lasted about 25 hours before ending shortly after midnight Sept. 6, according to Indonesia’s Center for Volcanology and Geological Hazard Mitigation, known as PVMBG or CVGHM.
Short, intermittent bursts of lava, ash and other volcanic material known as Strombolian eruptions have continued. Indonesia’s meteorological agency reported another small eruption on the morning of Sept. 8, but said the volcano’s overall intensity had declined.
The volcano remained at Level III, the second-highest alert on Indonesia’s four-tier scale. Officials warned that additional eruptions remained possible and advised residents, tourists and climbers to stay at least 3 kilometers, or nearly 2 miles, from the crater. PVMBG said possible hazards include falling volcanic rocks, heavy ashfall and lava flows.
A man cleans volcanic ash on an ambulance in Lampung province, Indonesia, Sept. 6, 2026. Indonesia's Soekarno-Hatta International Airport near Jakarta was temporarily closed early Sunday after volcanic ash from an eruption of Mount Anak Krakatau was detected in the airport area, disrupting dozens of flights, the Ministry of Transportation said. (Photo by Deden Iman/Xinhua via Getty Images)
The initial ash cloud temporarily closed eight airports on Java and Sumatra. All eight had reopened by Sept. 8 after ground testing found no volcanic ash around the runways and airspace, according to Indonesia’s Meteorology, Climatology and Geophysics Agency.
Winds were carrying the remaining ash south and southwest toward the Indian Ocean. With the eruption easing and most of the ash moving away from heavily populated areas, significant ongoing aviation disruptions appear unlikely. However, flights near Indonesia could still be affected if another stronger eruption occurs.
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