How a Tongan volcano flooded Australia
By Doug Mitchell
Published in the Australian Citizens Party's Australian Alert Service, 8 February 2023
In conversations with hundreds of Australians in the last few years, a phrase commonly heard when describing weather events is the conspiratorial “it’s geoengineering”. Such claims have never been accompanied with any scientific evidence to prove them. Neither “geoengineering” nor climate change were the cause of the record rainfall seen on the Australian continent in 2022. A major contributor to this rainfall was a volcanic eruption, possibly the largest in recorded human history, whose lasting impact ought to be given much greater attention by meteorologists. Thanks to Australian Alert Service subscriber Andrew Davies for bringing this to my attention.
The large eruption of the Hunga Tonga–Hunga Ha’apai undersea volcano in Tonga on 15 January 2022 sent ash and water vapour 57km into the atmosphere. Hunga Tonga and Hunga Ha’apai are two of 171 islands (only 45 of which are inhabited) in Tonga, whose total land surface area of 750 km2 is scattered across 700,000 km2 of the South Pacific Ocean. An article on FreeWestMedia describes how the height of the cloud was precisely measured, and says “The eruption was more than 4,000 times more powerful than the 15 kiloton atomic bomb the US dropped on Hiroshima and the most powerful since at least the 1883 eruption of the Krakatoa volcano in Indonesia, which triggered a global volcanic winter.” The eruption was heard more than 2,000 km away in New Zealand, while a series of bangs were heard in Alaska, USA. Atmospheric shockwaves went around the Earth four times.
Scientific journal Nature reported 8 June 2022 that in May that year a team of volcanologists from the University of Auckland, NZ, had “sailed over the volcano’s caldera, the central depression that forms when a volcano erupts, and used sonar to map its structure. They found the four-kilometre-wide caldera had dropped in depth from less than 200 metres below sea level [before the eruption], to more than 850 metres.” The article explains that the reason the eruption was so powerful was that as the centre of the caldera collapsed, 200 m of pressure forced huge amounts of 20 °C water into contact with the emerging 1,100 °C magma. Because of the huge temperature differential, the water instantly vapourised and exploded, resulting in several large blasts and hundreds of much smaller ones every minute. Eyewitnesses reported hearing “crackling and [a] noise like artillery fire” as far as 90 kilometres from the eruption.
Another researcher, Luis Millán at NASA’s Jet Propulsion Laboratory in Pasadena, California, said that the eruption increased the water-vapour content of the stratosphere by 146 teragrams (146 million tonnes), or 10 per cent, which will probably remain in the atmosphere for at least a year. “We haven’t seen anything like this before in the entire satellite era”, Millán said. A November 2022 study by the NZ National Institute of Water and Atmospheric Research (NIWA) showed that water vapor equivalent to 2.6 million Olympic swimming pools was thrown into the atmosphere. However you measure it, that is a lot of water!
On Australia’s record rain in 2022, a video on the OzGeographics YouTube channel describes how the water vapour from the volcano was carried west by the prevailing winds towards the Indian Ocean, and then interacted with other factors that already play a major role in our weather—La Niña, the Southern Annular Mode (SAM) and the Indian Ocean Dipole (IOD)—to amplify the rainfall. The SAM is the north-south movement of westerly winds in the middle to higher latitudes of the Southern Hemisphere. The volcano forced the SAM to stay further south near Antarctica for longer. A La Niña pattern occurs when cooler than normal water temperatures in the eastern Pacific Ocean strengthen the easterly trade winds, causing warmer than normal ocean temperatures to Australia’s north-east, which results in an increased chance of rain in eastern Australia. The IOD is the year-to-year differences in surface temperatures in the western and eastern Indian Ocean. The October floods occurred when the IOD was in a negative state (warmer than average near Indonesia, cooler near east Africa), which when combined with La Niña results in a lot of rain in eastern and southern Australia. When the volcano erupted, prevailing winds took water vapour west towards India then south towards Antarctica where it linked up with the winds from the SAM.
Why wasn’t the Tongan volcanic eruption given due recognition for its impact on our weather? FreeWestMedia says that measurements made between 15 January and 1 July by instruments on board NASA’s Aura atmospheric research satellite show that “as early as February, the water vapour and sulphur-rich aerosol particles separated into two distinct but overlapping air layers and spread until the end of June, as long as the measurement results were given. We therefore do not know what happened afterwards. … The gigantic cloud of gas and ash—which has spread over large parts of the earth—blocks solar penetration and lowers the temperature, both on the Earth’s surface and in the atmosphere.” According to a study “published by the United States Geological Survey (USGS), the Earth’s average temperature dropped by 0.5 to 0.7 degrees Celsius as a result of the eruption in the Philippines in 1991.” One study by University of Colorado atmospheric chemist Yunqian Zhu (et al.), published in Nature on 28 October 2022, showed that solar radiation after the eruption decreased by as much as 1-2 watts per square metre, a common occurrence in solar minimums, which our planet has been in since December 2019.
It’s time that our policymakers put basic climate science
in the spotlight, and give the microphone to scientists; and
that people everywhere think scientifically, rather than blaming some invisible “they” who allegedly control everything.
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