Tag: chaos

The prospect of climate chaos following major volcano eruptions

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It hardly needs saying that volcanoes present a major hazard to people living in close proximity. The inhabitants of the Roman cities of Herculaneum and Pompeii in the shadow of Vesuvius were snuffed out by an incandescent pyroclastic during the 79 CE eruption of the volcano. Since December 2023 long-lasting eruptions from the Sundhnúksgígar crater row on the Reykjanes Penisula of Iceland have driven the inhabitants of nearby Grindavík from their homes, but no injuries or fatalities have been reported. Far worse was the 1815 eruption of Tambora on Sumbawa, Indonesia, when at least 71,000 people perished. But that event had much wider consequences, which lasted into 1817 at least. As well as an ash cloud the huge plume from Tambora injected 28 million tons of sulfur dioxide into the stratosphere. In the form of sulfuric acid aerosols, this reflected so much solar energy back into space that the Northern Hemisphere cooled by 1° C, making 1816 ‘the year without a summer’. Crop failures in Europe and North America doubled grain prices, leading to widespread social unrest and economic depression. That year also saw unusual weather in India culminate in a cholera outbreak, which spread to unleash the 1817 global pandemic. Tambora is implicated in a global death toll in the tens of millions. Thanks to the record of sulfur in Greenland ice cores it has proved possible to link past volcanic action to historic famines and epidemics, such as the Plague of Justinian in 541 CE. If they emit large amounts of sulfur gases volcanic eruptions can result in sudden global climatic downturns.

The ash plume towering above Pinatubo volcano in the Philippines on 12 June 1991, which rose to 40 km (Credit: Karin Jackson U.S. Air Force)

With this in mind Markus Stoffel, Christophe Corona and Scott St. George of the University of Geneva, Switzerland, CNRS, Grenoble France and global insurance brokers WTW, London, respectively, have published a Comment in Nature warning of this kind of global hazard (Stoffel, M., Corona, C. & St. George, S. 2024.  The next massive volcano eruption will cause climate chaos — we are unprepared. Nature v. 635, p. 286-289; DOI: 10.1038/d41586-024-03680-z). The crux of their argument is that there has been nothing approaching the scale of Tambora for the last two centuries. The 1991 eruption of Pinatubo fed the stratosphere with just over a quarter of Tambora’s complement of SO2, and decreased global temperatures by around 0.6°C during 1991-2. Should one so-called Decade Volcanoes – those located in densely populated areas, such as Vesuvius – erupt within the next five years actuaries at Lloyd’s of London estimate economic impacts of US$ 3 trillion in the first year and US$1.5 trillion over the following years. But that is based on just the local risk of ash falls, lava and pyroclastic flows, mud slides and lateral collapse, not global climatic effects. So, a Tambora-sized or larger event is not countenanced by the world’s most famous insurance underwriter: probably because its economic impact is incalculable. Yet the chances of such a repeat certainly are conceivable. A 60 ka record of sulfate in the Greenland ice cores allows the probability of eruptions on the scale of Tambora to be estimated. The data suggest that there is a one-in-six chance that one will occur somewhere during the 21st century, but not necessarily at a site judged by volcanologists to be precarious . Nobody expected the eruption from the Pacific Ocean floor of the Hunga Tonga-Hunga Ha’apai volcano on January 15, 2022: the largest in the last 30 years.

The authors insist that climate-changing eruptions now need to be viewed in the context of anthropogenic global warming. Superficially, it might seem that a few volcanic winters and years without a summer could be a welcome, albeit short-term, solution. However, Stoffel, Corona and St. George suggest that the interaction of a volcano-induced global cooling with climatic processes would probably be very complex. Global warming heats the lower atmosphere and cools the stratosphere. Such steady changes will affect the height to which explosive volcanic plumes may reach. Atmospheric circulation patterns are changing dramatically as the weather of 2024 seems to show. The same may be said for ocean currents that are changing as sea-surface temperatures increase. Superimposing volcano-induced cooling of the sea surface adds an element of chaos to what is already worrying. What if a volcanic winter coincided with an el Niño event? The Intergovernmental Panel on Climate Change that projects climate changes is ‘flying blind’ as regards volcanic cooling. Another issue is that our knowledge of the effects in 1815 of Tambora concerned a very different world from ours: a global population then that was eight times smaller than now; very different patterns of agriculture and habitation; a world with industrial production on a tiny proportion of the continental surface. Stoffel, Corona and St. George urge the IPCC to shed light on this major blind spot. Climate modellers need to explore the truly worst-case scenarios since a massive volcanic eruption is bound to happen one day. Unlike global warming from greenhouse-gas emission, there is absolutely nothing that can be done to avert another Tambora.

The chaotic early Solar System: when giant planets went berserk

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Readers of Earth-logs will be familiar with the way gravitational interactions between the planets that orbit the Sun control cyclical shifts in each other’s rotational and orbital behaviours. The best known are the three Milankovich cycles. The eccentricity of Earth’s orbit (deviation from a circular path) changes according to the varying gravitational pulls exerted by Jupiter and Saturn as they orbit the Sun, and is dominated by 100 ka cyclicity. The tilt (obliquity) of Earth’s rotational axis changes in 41 ka cycles.  The direction in which the axis points relative to the Sun varies with its precession which has a period of about 25.7 ka. Together they control the amount of solar heating that our planet receives, best shown by the current variation in glacial-interglacial cycles. But the phenomena predicted by Milutin Milankovich show up in palaeoclimatic changes back to at least the late Precambrian. Climate changes resulting from the gravitational effect of Mars have recently been detected with a 2.4 Ma period. But that steady carousel of planetary motions hasn’t always characterised the Solar System.

Cartoon showing planet formation in the early, unstable Solar System (Credit: Mark Garlick, Science Source)

Observations of other stars that reveal the presence of their own planetary systems show that some have giant planets in much closer orbits than those that circuit the Sun. Others occur at distances that extend as far as the orbital diameters as those in the Solar System: so perhaps giant planets can migrate. A possibility began to be discussed in the late 1990s that Jupiter, Saturn, Uranus and Neptune – and a fifth now-vanished giant planet – were at the outset in neat, evenly-spaced and much closer orbits. But they were forced outwards later into more eccentric and generally askew orbits. In 2005, planetary astronomers gathered in Nice, France to ponder the possibilities. The outcome was the ‘Nice’ Model that suggested that a gravitational instability had once emerged, which set the Solar System in chaotic motion. It may even have flung gigantic masses, such as postulated fifth giant planets, into interstellar space. This upheaval may have been due to a rapid change in the overall distribution of mass in the Solar System, possibly involving gas and dust that had not yet accreted into other planets or their planetesimal precursors. Chaotic antics of monstrous bodies and shifts in their combined gravitational fields can barely be imagined: it was nothing like the staid and ever present Milankovich Effect. Geologists have reconstructed one gargantuan event that reset the chemistry of the early Earth when it collided with another body about the size of Mars. That  also flung off matter that became the Moon. Evidence from lunar and terrestrial zircon grains (see: Moon-forming impact dated; March 2009) suggests the collision occurred before 4.46 billion years ago (when parts of both eventually crystallised from magma oceans), Solar System having begun to form at around 4.57 Ga. Could formation of the Moon record the early planetary chaos? Others have suggested instead that the great upheaval was the Late Heavy Bombardment, between 4.1 and 3.8 Ga, which heavily cratered much of the lunar surface and those of moons orbiting the giant planets.

Another approach has been followed by Chrysa Avdellidou of the University of Leicester, UK and colleagues from France and the US (Avdellidoli, C. et al. 2024. Dating the Solar System’s giant planet orbital instability using enstatite meteorites. Science, v. 384, p. 348-352; DOI: 10.1126/science.adg8092) after discovery of a new family of asteroids: named after its largest member Athor. The composition of their surfaces, from telescopic spectra, closely matches that of EL enstatite chondrite meteorites. Dating these meteorites should show when their parent asteroids – presumably the Athors – formed.  Using argon and xenon isotopes Mario Trieloff  and colleagues from the University of Heidelberg, Germany in showed that the materials in EL enstatite chondrite meteorites were assembled a mere 2 Ma after the Solar System formed (Trieloff, M. et al. 2022. Evolution of the parent body of enstatite (EL) chondrites. Icarus, v. 373, article 114762; DOI: 10.1016/j.icarus.2021.114762). Be that as it may, that the evidence came from small meteorites shows that the parent body, estimated as having had a 240 to 420 km diameter, was shattered at some later time. Moreover, at that very early date such bodies would have contained a ready heat source in the form of a short-lived isotope of aluminium (26Al) which decays to stable 26Mg, with a half-life of 0.717 Ma. 26Al is thought to have been produced by a supernova that has been suggested to have triggered the formation of the Solar System. Excessive 26Mg is found in many meteorites, evidence for metamorphism formed by such radiogenic heat. They also record the history of their cooling.

Avdellidoli et al. estimate that the 240 to 420 km Athor parental planetesimal had slowly cooled for at least 60 Ma after it formed. When it was shattered, the small fragments would have cooled instantaneously to the temperature of interplanetary space – a few degrees above absolute zero (-273.2 °C). From this they deduce the age of the chaotic restructuring of the early Solar System to be at least 60 Ma after its formation. Other authors use similar reasoning from other chondritic meteorite classes to suggest it may have happened even earlier at 11 Ma. But there are other views for a considerably later migration of the giant planets and the havoc that they wrought. The only widely agreed date, in what seems to be an outbreak of wrangling among astronomers, is for the Moon-forming collision: 110 Ma after formation of the Solar System. For me, at least, that’s good-enough evidence for when system-wide chaos prevailed. The Late Heavy Bombardment between 4.1 and 3.8 Ga seems to require a different mechanism as it affected large bodies that still exist. It may have resulted from whatever formed the asteroid belt, for it was bodies within the range of sizes of the asteroids that did the damage, in both the Inner and Outer Solar System.

See also: The instability at the beginning of the solar system. MSUToday, 27 April 2022: Voosen, P. 2024. Giant planets ran amok soon after the Solar System’s birth. Science, v. 384 news article eadp8889; DOI: 10.1126/science.adp8889