The "unusual" period from 1983 to 2008 was actually consistent with human-induced climate change, said the researchers from the National Institute of Water and Atmospheric Research (NIWA) and Victoria University.
At least 58 New Zealand glaciers advanced during the period when the vast majority of glaciers worldwide shrank, an anomaly that was never satisfactorily explained previously, said lead-author Associate Professor Andrew Mackintosh, of Victoria University's Antarctic Research Centre.
"We found that lower temperature caused the glaciers to advance, rather than increased precipitation as previously thought," Mackintosh said in a statement.
"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," he said.
"It may seem unusual, this regional cooling during a period of overall global warming, but it's still consistent with human-induced climate change. The temperature changes were a result of variability in the climate system that's specific to New Zealand," he said.
"New Zealand sits in a region where there's significant variability in the oceans and the atmosphere, much more than many parts of the world. The climate variability that we identified was also responsible for changes in the Antarctic ice sheet and sea ice during this period."
Although glaciers advancing sounded promising, the future "doesn't look good" for New Zealand's glaciers, said Mackintosh.
"New Zealand's glaciers are very sensitive to temperature change. If we get the 2 to 4 degrees (centigrade) of warming expected by the end of the century, our glaciers are going to mostly disappear. Some may experience small-scale advance over that time due to the regional climate variability, but overall they will retreat."
[Xinhua/China]
15/2/17
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