Krakatoa heralded atmospheric sciences & era of global disaster; today, it would cool world climate but not mitigate it

Most of us have seen the painting ‘Scream’ by Norwegian artist Edvard Munch. But most of us may not know the backstory to it. The painting was Munch’s depiction of an event that took place 141 years ago: The eruption of the volcano on Krakatoa (Krakatau) island in the Dutch East Indies (today’s Indonesia) on August 27, 1883.

Krakatoa is noteworthy in more ways than one. It is known for the records it set as a volcano. But even more than that, it was the first ‘global disaster’ as the telegraph, which had been invented by then, spread the news worldwide.

The volcanic eruption is even more important as it inspired interest in volcanoes and their effect on climate like never before. Today, Krakatoa is a watershed moment in global climate history. Even more importantly, it is still active and can erupt again.

The boom heard around the world

Krakatoa is a group of four islands — Sertung (Verlaten), Panjang (Lang), Rakata, and Anak Krakatau — located in the Sunda Strait that separates Indonesia’s two main islands of Sumatra and Java. Administratively, it is part of Lampung province on Sumatra and faces the Banten and Jakarta provinces on Java, just across the sea.

It is Krakatoa’s location that is especially important. That is where the Indo-Australian tectonic plate subducts or goes under the Eurasian plate — leading to the formation of several faults and fractures. The area is thus extremely hazardous seismically, with huge risks of large earthquakes and tsunamis.

“In 1883, Krakatoa was an unpopulated island composed of three volcanoes, Danan, Perbuatan and Rakata… On the 20th of May 1883 Perbuatan showed again signs of activity: an 11 km long ash and water vapour column could be seen from Java and Sumatra. During the three following months small eruptions accompanied by earthquakes occurred from time to time,” according to the 2009 paper Climate effects of the 1883 Krakatoa eruption: Historical and present perspectives.

It adds that these warning signs did not trigger alarm among either the Indonesians or the colonial Dutch authorities. This was because the Perbuatan volcano “was considered too small to be dangerous”.

However, what they did not know was that the three volcanoes were actually three volcanic cones related to the same huge magma chamber.

“The main eruption occurred on the 26th and the 27th of August 1883. The lava and gases were ejected from both the Perbuatan and the Danan volcano to approximately 50 km height. The magma chamber emptied itself very quickly and collapsed, such that only half of the Rakata volcano remained…,” the authors note.

The sound of the August 1883 eruption was heard around one third of the planet, according to another paper, The blessing of the ‘year without summer’: Climatic and socioeconomic impact of the Krakatoa eruption (1883) in the South-east of the Iberian Peninsula, published in 2021.

Almost immediately, tsunamis were generated and reached the coasts of South Asia, East Africa, and Western Australia.

The pyroclastic flow generated by the volcano killed about 1,000 people in Ketimbang on the Sumatra coast, about 40 km north of Krakatoa. All 3,000 inhabitants of the island of Sebesi, approximately 13 km from Krakatoa, were killed.

“…The official fatality count recorded by the Dutch authorities was 36,417, and many inhabited areas were destroyed,” according to the 2021 paper.

As per the authors of a 2023 paper, An Assessment of The Scientific Value of Krakatoa, Indonesia From a Geoheritage Perspective Journal of Applied Geoscience and Engineering, “Krakatoa is the second world's largest death toll after Tambora (1814 AD)”. Tambora is also located in Indonesia.

Sun, moon and no summer

There was more to come. Rogier D M Verbeek, a Dutch geologist and the first man to dock on the remains of the Krakatoa Island a few months after the eruption, calculated the volume of material ejected by the Krakatoa volcano to be about 20 cubic km, around ten times less than Tambora.

The 2009 paper notes that “the darkness caused by the ash rain persisted for three days after the onset of the Tambora eruption, in contrast to only a few hours after the Krakatoa eruption. Verbeek further wrote that the ejected gases and ashes were pushed into the upper-air currents, in 15-20 km height, where they would freeze and then travel as tiny crystals around the globe”.

This was because Krakatoa and Indonesia are located right on the equator. “Tropical eruptions may affect the global climate system as the volcanic cloud can spread to both hemispheres, while mid-latitude and high-latitude eruptions mainly affect the hemisphere in which they occur,” the 2021 paper notes.

The eruption caused a ‘global optical effect’. In Europe and North America, there were vivid red sunsets, purple, blue-greenish, and red for many months.

“This phenomenon lasted until October 21, 1883, and has been depicted in various artworks, such as The Scream by Norwegian artist, Edvard Munch,” as per the 2023 paper.

The 2021 paper adds that “the magnitude was such that the warming of the ocean and the rise in sea level in the twentieth century was substantially delayed by oceanic cooling resulting from this eruption”.

As per the Natural History Museum UK, Krakatoa “cooled the entire Earth by an average of 0.6°C for months to come”.

In the years following Krakatoa, more eruptions took place, spurring greater interest in the link between volcanoes and climate change.

“The succession of major eruptions (Krakatoa in 1883, Tarawera in 1886, Santa María in 1902 and Katmai in 1912), the growing presence of instrumental meteorological data, and widespread scientific curiosity meant that during the first half of the twentieth century, many empirical studies were conducted on the relationship between large volcanic eruptions and weather,” the 2021 paper notes.

Krakatoa today

What if Krakatoa erupted today? Certainly, there are warning signs.

In 1927 and 1928, the world first got to know that the Krakatoa was back. This time, it was called Anak Krakatau, or ‘child of Krakatau’ in the Dutch East Indies.

“The first indication of the Mount Anak Krakatau embryo’s existence occurred on December 29, 1927, to January 5, 1928, as an underwater volcano at a depth of 28 meters below sea level,” a 2022 paper, Community Resilient from Anak Krakatau Eruption: Lesson Learn from The Tale of Lampung Submerged to Increase Environmental Awareness, noted.

Anak Krakatau has erupted in 2018, 2020, 2022 and 2023. The eruption in December 2018, killed 437 people and displaced 40,000 people.

But will there be an eruption like the one in 1883? The Sixth Assessment Report of the Intergovernmental Panel on Climate Change has suggested that one such eruption is likely this century, as reported by Rohini Krishnamurthy of Down To Earth (DTE).

What about global warming? A recent study by researchers from the University of Cambridge and the UK Met Office, says that “large-magnitude eruptions will have greater effects as the climate continues to warm.”

“If such an eruption occurs, it would therefore temporarily and partially mask human-caused climate change,” DTE reported, citing the IPCC report.

DTE has also reported that “Heavy rainfall and melting of glaciers might lead to frequent and severe volcanic eruptions.”

It promises to be an interesting century as far as the link between vulcanology and climate change is concerned.