Ozone season expected to be early, long-lasting this summer, NIWA says

An early and long-lasting ozone hole in the atmosphere is being predicted by NIWA (the National Institute of Water and Atmospheric Research) this year.

Principal atmosphere and climate scientist Dr Olaf Morgenstern said he had a hunch the ozone season would be longer than usual, due to a combination of climate change and last year's volcanic eruption in Tonga.

"There's a cooling trend in the stratosphere that has resulted in the ozone hole decaying later in its seasonal cycle and lasting a bit longer than we would otherwise have.

"The other side of the story is that a year and a half ago we had this big volcanic eruption that injected a very large amount of water vapour into the stratosphere, further exacerbating the trend that's otherwise driven by other greenhouse gases."

The Antarctic ozone hole typically reaches its greatest extent in September or October and disappears in November or December.

Ozone molecules absorb ultraviolet radiation from the sun, acting like sunscreen for life on Earth. Too much UV can cause problems such as skin damage and a fall in ocean phytoplankton, which can impact the food chain.

Morgenstern said the Hunga-Tonga-Hunga Ha'apai sent an astonishing amount of water vapour into the atmosphere, which caused the stratosphere to cool and enhanced the depletion of ozone by forming clouds above Antarctica.

He said the stratosphere was very sensitive to changes in temperature, with climate change causing a long-term cooling trend, which could be contributing to the cold and stable conditions seen at present.

New Zealand would see the effects of ozone depletion in December through January, which coincided with the sun being at its highest point on the horizon, he said.

Morgenstern said people should be vigilant with sun protection to avoid getting burnt.

He said some people might think the hole in the ozone layer was no longer a problem, due to the 1987 Montreal protocol to ban human-produced ozone-depleting chemicals like chlorofluorocarbons and the falling rates of chlorine in the stratosphere over the past 25 years, but it was still about six times above its natural level.

Morgenstern said it was likely to be mid-2060 before the hole in the ozone layer started disappearing.

"While the reduction in chlorine in the stratosphere will eventually lead to a closure of the ozone hole, it doesn't happen very fast."

NIWA atmospheric scientist Dr Richard Querel said the organisation was working with Nasa and Antarctica NZ to measure the chemistry in the atmosphere, with a balloon to be launched to gather airborne data, to get a better understanding of what was going on.