Tongan eruption's sulphur dioxide could lead to cooler winter

Vandhna Bhan
Source: 1News

A huge amount of sulfur dioxide is lingering in the atmosphere after Mt Hunga Tonga-Hunga Ha'apai erupted in Tonga on Saturday, and it could mean changes to New Zealand’s climate.

This invisible pollutant, 30km up in the atmosphere, is causing extraordinary sunsets and sunrises across the southern hemisphere.

Experts say we can expect to see more vivid and purple sunsets over the winter months, along with perhaps a cooler season ahead.

When a volcano erupts, it releases a large amount of sulfur dioxide into the air.

Right now, there's a high concentration in the troposphere, but if a lot reaches the stratosphere, then it's converted to sulfuric acid, which then reflects sunlight, and lowers temperatures.

"New Zealand temperatures do correlate with large volcanic eruptions. There have been six or seven volcanic eruptions over the last 150 years that have directly affected New Zealand temperatures," NIWA climate scientist Dr Sam Dean said.

Thirty years ago the eruption of Pinatubo in the Philippines cooled the earth by one degree for the next year and a half, but it's unlikely that will happen this time round.

"Pinatubo released 10 to 15 megatonnes of sulfur dioxide. This only released or emitted 0.4 megatonnes of sulfur dioxide," said climate scientist Dr Jim Salinger, who's researched the impacts of large volcanic eruptions on the climate.

Tonga's eruption is around 40 times smaller than that of Pinatubo, so any effects will be localised and minimal.

"There might be a tiny cooling but it'll probably be barely detectable might be a few tenths of a degree centigrade but not for very long," Salinger said.

"It's not going to have any impact on global warming. the cooling from this eruption because of the sulfate aerosols and the mist will be too small to have any detectable impact on global warming unfortunately.”

For now, the direct threat of this eruption remains for those in the Pacific, the area now having the world's highest concentration of sulfur dioxide in the air, leading to warnings for Fiji to expect acid rain over the coming days.

"Acid rain can be dangerous to people who are in the vicinity of the volcano. And from the sulfur dioxide gas you can get volcanic smog which can be dangerous to inhale for long periods of time as well as the ash itself," Dean said.

Fijian residents are being urged to stay inside as it rains, to not consume tank water and to wash any vegetables and produce.