The cooling effect of Tonga's volcano eruptions is much smaller than initially thought and not strong enough to overwhelm longer-term global warming tendency, an analysis has shown.

The Hunga Tonga-Hunga Ha'apai volcano near Nuku'alofa, capital of Tonga, erupted violently and triggered a tsunami in January.

It has raised wide public concern about the impact on global climate since sulfur dioxide injected into the stratosphere after eruptions was oxidized and converted to sulfate aerosols.

These aerosols linger for one or two years and reduce incoming solar radiation, resulting in a short period of global cooling.

A previous estimate placed the reduction in global surface air temperature at between 0.03 and 0.1 degrees Celsius over the next one to two years.

The study, led by Chinese scientists and published Tuesday in the journal Advances in Atmospheric Sciences, showed that the strongest cooling impact of the volcano would be more than 0.01 degrees Celsius in parts of Australia and South America and the cooling over most of China will be less than 0.01 degrees Celsius.

They found that the global surface temperature will be decreased by only 0.004 degrees Celsius in 2023 due to the eruptions.

One or two volcanic eruptions are not enough to alter the long-term global warming trend unless there are clusters of volcanic eruptions that can persist through centuries, as is suggested to have happened during the Little Ice Age in the past millennium, according to the study.

"Southern Hemisphere volcanic eruption emissions are largely confined to circulating in the same hemisphere and the tropics, with less of an impact on the Northern Hemisphere," said Zhou Tianjun, the paper's corresponding author and a researcher at the Institute of Atmospheric Physics at the Chinese Academy of Sciences.

"This, in turn, leads to a weaker global cooling than those of northern hemispheric and tropical volcanoes," Zhou added.

For more: 

Could Tonga volcano eruption cool the climate?

(Cover image via CFP.)

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