TLDR: Massive volcanic eruptions can impact global climate and severely disrupt global critical infrastructure. These eruptions are more frequent than previously thought, can have more impact than previously thought, and at lower magnitudes than previously thought. New Zealand (NZ) is less likely to suffer direct effects of climate disturbance, but is highly vulnerable to trade disruption. Massive volcanism constitutes a significant global risk, and a nationally significant risk to New Zealand, even if originating elsewhere. A publicly facing National Risk Register would make this clear and encourage mitigation.
New book on Global Risk
A new free book on existential risks to humanity appeared recently. The Era of Global Risk: An introduction to existential risk studies from OpenBook Publishers is edited by SJ Beard, Lord Martin Rees, Catherine Richards, and Clarissa Rios Rojas.
The book surveys familiar existential risks such as ecological breakdown, biological threats including bioengineered pandemics, and risks from advanced artificial intelligence, especially its convergence with risk from nuclear weapons. Many of these threats are hot current topics in global risk management. But the book also includes a very good discussion of natural risks such as volcanic activity and near-Earth objects.
Risk from large magnitude volcanoes
In this blog I focus on volcano risk. NZ is very familiar with the harm volcanoes can cause. On 24 December 1953, 151 people were killed in the Tangiwai railway disaster when a volcanic lahar washed out a rail bridge. On 9 December 2019 another 22 people were killed by an eruption of Whakaari/White Island. There have been several other volcanic fatalities in NZ.
There are clearly risks to NZ from volcanic eruptions occurring within NZ, but there are also risks from volcanic eruptions occurring elsewhere, the effects of which cascade to, potentially severely, impact NZ. Not all these effects are direct threats to life, but indirectly they could cause economic and societal catastrophe.
The fossil record indicates the huge impact that supervolcanism (VEI 8+) has had for life on Earth. Most past global mass extinction events were associated with massive volcanism. The causal process was probably rapid climate cooling or warming (or both) and pervasive marine anoxia. This is because volcanoes can spew sulphur into the atmosphere, reflecting sunlight, and absorbing heat from Earth. Clearly, supervolcanic eruptions could make agriculture difficult in many regions.
Even lesser volcanism (VEI 7+) has been associated with global climate impacts. For example, the Tambora eruption of 1815 brought unseasonal frost and famine to regions of the world including parts of Europe, India, and China.
More frequent than previously thought
The climate impacts of volcanism depend on the amount of sulphur emitted, which does not necessarily align with the magnitude of the eruption. VEI 6 & 7 are capable of climate effects. The chapter on Natural Global Catastrophic Risks mentions the occurrence of 160 explosive eruptions ejecting more sulphur than Tambora 1815, in the last 10,000 years, with evidence of additional large eruptions being frequently discovered.
Considering the totality of geological and historical evidence it is likely that the recurrence interval for VEI 7+ eruptions is about once every 625 years (a 1 in 6 chance this century). The table shows the recurrence period of other magnitude eruptions.
More harmful than previously thought
Anthropogenic greenhouse gas emissions are interfering with effect of volcanoes via the Brewer-Dobson circulation (an atmospheric pattern where warm air rises in the tropics and sinks at the poles). The effect of this is that future eruptions the size of Tambora in the tropical regions could cause up to 3.2C global surface cooling. For context, the 1.9C mean global cooling caused by Tambora in 1815 led to summertime frost days in Europe.
Additionally, if large eruptions (even as small as VEI 3+) were to occur at global trade and infrastructure pinch points (eg Luzon Strait or many other places where trade, communications, commerce, etc all converge), the impact on trade, geopolitics, and economies could be severe. This volcano pinch point risk was described in detail in a paper in Nature in 2021. The effects could include widespread food shortages, fuel price rise, disease outbreaks, trade isolation, or conflict.
New Zealand is more vulnerable to trade disruption
Our previous research showed that islands were less impacted by the climate effects of the 1815 Tambora eruption than continental locations. Although this may not protect islands today in a more interconnected world where a global food shock could cascade to widely impact trade, including food and energy supply.
New Zealand is particularly vulnerable to the effects of trade disruption given its dependence on liquid fuel imports, with only a short term (weeks) onshore reserve. Diesel is necessary for agricultural production, and transport of food and manufactured goods. New Zealand’s digital communications are vulnerable to destruction of undersea cables or overseas cloud infrastructure, and the electricity system is dependent on imported parts for maintenance and is calibrated to our usual levels of sunlight, rainfall, and wind. There are many other ways in which New Zealand society could be strained or break down due to major catastrophes occurring elsewhere. I have blogged on these issues many times previously and won’t cover them again here.
Risk management
The NZ Institute of Geological and Nuclear Sciences and the National Emergency Management Agency work closely in New Zealand on risk from volcanoes within the country. But it is not clear who is tasked with assessing the likelihood and societal and economic consequences of massive volcanism originating elsewhere. We identified a similar apparent gap with respect to the risk to New Zealand from a Northern Hemisphere nuclear war – and this led to our current Aotearoa NZ Catastrophe Resilience Project (NZCat), where we have profiled the nuclear risk, and are researching strategies for mitigation.
The UK’s publicly facing National Risk Register (2023) now includes global VEI7+ eruption, recognising the dire trade, food, economic, and geopolitical consequences of such an event and the impact this could have on the UK. Norway’s 2014 National Risk Assessment also includes large volcanoes manifesting elsewhere.
If risks are described and understood, civil contingencies can be taken ahead of time to mitigate the impacts on New Zealand (or by other countries in similar circumstances), but only if risk information and advice is provided to Government, businesses, and society. A publicly facing NZ National Risk Register is needed.
Practical steps for mitigation likely include such things as decreasing dependence on imported diesel through electrification or other alternatives, measures to enhance fuel security such as increased storage and biofuel production, diversified trade options, more heterogenous local manufacturing, diversified and less energy intensive agriculture, and frost resistant cropping. Many of these are things that would tend to help us achieve other important goals such as climate change mitigation and resilience to a range of other disasters. Additionally, plans for response specific to significant ‘abrupt sunlight reduction scenarios’ (eg volcanic or nuclear winter) can be prepared ahead of time, and organisations such as the Alliance to Feed the Earth in Disasters (ALLFED) specialise in such planning.
It’s time New Zealand compiles a proper catalogue of nationally significant risks that looks beyond those we are familiar with.
Adapt Research Ltd 