The Antarctica ozone hole is the smallest it has been in five years, according to research from Niwa, the National Institute of Water and Atmospheric Research.

Satellite data combined with ground-base measurements show the hole reached a maximum area of about 22 million square kilometres this year, compared with 24 million sq km last year.

While a one-year reduction in the ozone hole did not indicate a recovery stage, Niwa atmospheric scientist Stephen Wood said the new information added to a pattern of less severe ozone holes in recent years.

"We see a lot of year-to-year variation in ozone holes, caused by differences in atmospheric temperature and circulation. So we can't definitively say the ozone hole is improving from one new year of observations," Dr Wood said.

"However, we have now had a few years in succession with less severe holes. That is an indication we may be beginning to see a recovery."

The Antarctic ozone hole forms in August and September each year, remaining until it breaks up in November or December.

The largest the hole was ever recorded as being was in 2000, when it reached about 29 million sq km.