Regional climate variability caused an unusual period in which some of New Zealand's glaciers grew bigger, while glaciers worldwide were shrinking, a new study shows.

The research, carried out by scientists from Victoria University and the National Institute of Water and Atmospheric Research (Niwa), is published todayin scientific journal Nature Communications.

At least 58 New Zealand glaciers advanced between 1983 and 2008, with Franz Josef Glacier advancing nearly continuously during this time.

"Glaciers advancing is very unusual, especially in this period when the vast majority of glaciers worldwide shrank in size as a result of our warming world," said lead author Associate Professor Andrew Mackintosh, from Victoria's Antarctic Research Centre.

"This anomaly hadn't been satisfactorily explained, so this physics-based study used computer models for the first time to look into it in detail.

"We found that lower temperature caused the glaciers to advance, rather than increased precipitation as previously thought.

"These periods of reduced temperature affected the entire New Zealand region, and they were significant enough for the glaciers to re-advance in spite of human-induced climate change."

Mackintosh said the climate variability, which includes the cooler years, still reflected a climate that's been modified by humans.

"It may seem unusual. This regional cooling during a period of overall global warming but it's still consistent with human-induced climate change."