A Historical Volcanic Winter & Future Sunlight-Blocking Catastrophes: New Study

Nick Wilson & Matt Boyd

Summary / TLDR:

  • Island nations may have potential long-term survival value for humanity in global catastrophes eg, during a “nuclear winter” or “volcanic winter”.
  • We studied a major historical eruption (Mt Tambora in 1815), and found that the “volcanic winter” impacts were less in the islands than on the continents (for latitudinally equivalent comparisons).
  • Out of the 31 islands studied, the smallest temperature drops were seen for islands in the Southern Hemisphere, the Indian Ocean, and in the tropics and subtropics of the Southern Hemisphere.
  • Island nations could work to enhance their resilience to sunlight-blocking catastrophes to help ensure humanity can survive such events.

Our Study of the 1815 Mt Tambora eruption

Catastrophes such as nuclear war and large magnitude volcanic eruptions could fill the stratosphere with sun-blocking material such as soot or sulphur dioxide. Island nations may have potential long-term survival value for humanity in such sun-blocking catastrophes. We aimed to explore this further by studying the impact on islands after the largest historically observed volcanic eruption: that of Mt Tambora in Indonesia in 1815.

In conjunction with colleagues from Switzerland and the UK, our just published study1 involved 31 large, populated islands for which we conducted literature searches for relevant historical and palaeoclimate studies. We also analysed results from a reconstruction (EKF400v2), which uses atmospheric-only general circulation model simulations with assimilated observational and proxy data.

How did islands fare in the “volcanic winter” after the eruption?

From the literature review, there was widespread evidence for weather/climate anomalies in the years 1815-1817 for these islands (29/29 for those with data; Figure 1, below). But missing data was an issue for other dimensions such as impaired food production (seen in 8 islands out of only 12 with data). Data on food insecurity or famines was also largely missing, but for the 12 islands with data, four definitely experienced such problems. These were all in the North Atlantic region ie, Great Britain, Ireland, Iceland and Newfoundland. In three of these there was also evidence of food riots or demonstrations (ie, all except Iceland). In Ireland there was also evidence of increased death rates from famine and/or famine-related disease.

Based on the EKF400v2 reconstruction for temperature anomalies (compared to the relatively “non-volcanic” reference period of 1779 to 1808), the islands had lower temperature anomalies in the 1815-1818 period than latitudinally equivalent continental sites (at 100 km and 1000 km inland). This was statistically significant for the great majority of the comparisons for group analyses by hemisphere, oceans, and temperate/tropical zone.

Figure 1: Summarised evidence for impacts from the Tambora eruption on 31 islands in the 1815-1817 period (see the published article for additional details; Image produced using Ferret v7.63; Reproduced from Wilson et al 20231 (published under a Creative Commons Attribution 4.0 International License, http://creativecommons.org/licenses/by/4.0/)

When considering just the islands, all but four showed statistically anomalous temperature reductions in the 1816-1817 period (for most p<0.00001; with Figure 2 (below) showing the pattern for 1816). In the peak impact year of 1816, the lowest anomalies were seen for islands in the Southern Hemisphere (p<0.0001), the Indian Ocean (p<0.0001), and in the tropics and subtropics of the Southern Hemisphere (p=0.0057). The latter included the islands of: Australia [a continental island], Java, Madagascar, Marajó (Brazil), New Britain (part of Papua New Guinea [PNG]), New Guinea (PNG) and Timor.

Figure 2: Reconstructed temperature anomalies in 1816 (“the year without a summer”) relative to the “non-volcanic” reference period (1779 to 1808) using monthly data from the reconstruction EKF400v2 (Image produced using Ferret v7.63; Reproduced from Wilson et al 20231 (published under a Creative Commons Attribution 4.0 International License, http://creativecommons.org/licenses/by/4.0/)

Relevance to island refuges – for humanity to survive catastrophes

We might draw some provisional conclusions relevant to the concept of island refuges for humanity from this study. The findings do point to the likely benefits of island refuges in the Southern Hemisphere, the Indian Ocean and the tropics and subtropics of the Southern Hemisphere. Such islands may have features that advantage them in some catastrophes and could be considered for resilience building measures with the aim of ensuring humanity’s survival, especially in case much larger eruptions or nuclear war eventuate.

But other considerations for targeting resilience investments include the following:

  • The findings of simulation studies of the global climate impacts of nuclear war – which also favours Southern Hemisphere islands, including Aotearoa NZ (as we have studied here 2).
  • The risk of islands being directly attacked in a nuclear war (eg, those in military alliances with nuclear weapon states such as Australia, Iceland and Japan).
  • Capacity of islands to survive extreme pandemics (as we have studied here 3)
  • And the islands having the socio-economic and technological characteristics to potentially be a “node of persisting complexity” 4 from which more technologically advanced societies could be re-built.

Ideally a number of island nations could build up their resiliency to best survive such catastrophes, perhaps with initial focus on energy, food, transport and communications resilience. Well-placed islands might be provided with support to do so by the international community. But failing such international support – individual nations such as Australia and New Zealand should give consideration to doing this – for both themselves and the future of humanity.


1.         Wilson N, Valler V, Cassidy M, Boyd M, Mani L, Brönnimann S. Impact of the Tambora Volcanic Eruption of 1815 on Islands and Relevance to Future Sunlight-Blocking Catastrophesdair. Sci Rep. 2023;13:3649.

2.         Boyd M, Wilson N. Island refuges for surviving nuclear winter and other abrupt sunlight-reducing catastrophes. Risk Analysis. 2022.

3.         Boyd M, Wilson N. Optimizing island refuges against global catastrophic and existential biological threats: Priorities and preparations. Risk Analysis. 2021;41(12):2266-85.

4.         King N, Jones A. An Analysis of the Potential for the Formation of ‘Nodes of Persisting Complexity’. Sustainability. 2021;13(15):8161.

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