Will The Tonga Volcano Influence Global Climate?

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Will The Tonga Volcano Influence Global Climate?



Height in Atmosphere/


Most Recent Example
0: non-explosive


<100 meters


Kilauea, Hawaii (1977)
1: small


100 meters to 1 kilometer


Raoul Island, Near Tonga (2006)
2: moderate


1-5 kilometers

Every 2 weeks

Whakaari, New Zealand (2019)
3: moderate


3-15 kilometers

3 months

Cumbre Vieja, Canary Islands, Spain (2021)
4: large


15-25 kilometers

18 months

La Soufriere, Saint Vincent (2021)
5: very large


>25 kilometers

12 years

Mt. St. Helens (1980)
6: very large


>25 kilometers

50-100 years

Mt. Pinatubo, Philippines (1991)
7: very large


>25 kilometers

500-1,000 years

Mt. Tambora, Indonesia (1815)
8: very large


>25 kilometers

>50,000 years

Taupo, New Zealand (26,500 BC)

Table 1: The Volcanic Eruptive Index scale, description (classification), height of explosion, frequency and most recent example. Very preliminary estimates are that the Tonga VEI is in the 4-5 range. VEI of 4 or greater will affect the global climate.

Discussion: Early estimates of the volcanic eruptive index (VEI) of the Tonga Volcano are in the VEI = 4/VEI = 5 range. This estimate is based on the projected height of the eruptive plume at 20,000 kilometers (about 12.5 miles). Based on the uncertainty of this estimate according to various sources, the plume could be higher. Some scientists are saying the eruptive size is the greatest of this century. Based on the information in Table 1, there is potential for the Tonga Volcan to be the largest since Pinatubo in 1991.

While the strength of Tonga is not yet quantified and the VEI = 4/VEI = 5 preliminary estimate is speculative, there is certainty that Tonga’s eruption reached well into the stratosphere which automatically qualifies Tonga for at least a VEI =4 classification. VEI = 4 (or above) influence global climate. The eruptive outflow into the stratosphere indicates the particulates will navigate the globe initially at low latitude but spread pole ward with time. There is no rain to wash the particulates out of the stratosphere, so they are long lasting and consequently affect climate mostly by affecting solar intensity. Tonga will be a climate influencer, but the exact character is not known and will likely be unique to this volcano (rather than exactly like other VEI = 4/VEI = 5 eruptions).

Generally, low latitude powerful volcanic eruptions have a greater ability to influence climate as the outflow is more easily spread throughout both hemispheres. The Tonga volcano is near 21S latitude therefore more likely to initially influence the southern hemisphere but eventually the northern hemisphere.

Summary: The Tonga Volcano VEI classification is certain to be at least 4 and possibly 5 which automatically qualifies the volcano as a likely influencer of global climate. Early speculation is that Tonga is the strongest volcanic eruption since Pinatubo in 1991.