2017: When the weather went wild
First seven months of the year saw eight states of emergency declared and damage costing insurers $242m
THawke’s Bay • Port Hills, Christchurch • Whanganui, Rangitikei • Edgecumbe • Bay of Plenty • Thames-Coromandel • Whakatane • Nationwide severe weather • Dunedin flooding • Port Hills fires • Upper North Island flooding • Cyclone Debbie remnants • Cyclone Cook remnants • Nationwide snow/wind/ rain • South S Island flooding • his year is shaping as one of New Zealand’s worst for extreme weather events, following a spate of major fires, floods and storms.
Civil Defence declared a record number of weather-related state of emergencies — eight, compared with one last year and four in 2015.
Insurers have put losses from the year’s events, all of which hit in the first seven months, at $242 million — five times that of 2016‘s bill for extreme weather and also eclipsing other years.
Meteorologists say it’s not simply climate change at play, but a combination of ocean-driven effects that happened to make for a dramatic year. 2017 was tracking to finish somewhere between New Zealand’s seventh and fourth hottest on record, with this month’s heat likely pushing it toward the warmer end of the scale.
Niwa meteorologist Ben Noll said the year had been effectively bookended by a weak La Nina climate system that quickly faded away in February and March, and a much stronger one that kicked into gear last month. In between, nearly every month of the year had been either near or above average.
“We had five months of near average temperatures and five months of above-average temperatures — and just one month, January, that had below-average temperatures.
“August was 1.3C above average, October was 1C above average and November was 1.1C above average —
We had just one month, January, that had belowaverage temperatures. Niwa meteorologist Ben Noll
so you had some big boppers in there that were really pulling the weight at the top end.”
But the year still started dry enough in places to fuel large fires: notably blazes that scorched 2000ha of Christchurch’s Port Hills in February, destroying 11 homes, and three weeks of fires in Hastings that led to a state of emergency being declared.
Then came a series of major storms that battered the North Island, among them the remnants of Cyclone Debbie, which put much of Edgecumbe under water and forced the evacuation of 1600 residents, and Cyclone Cook soon after, which left thousands of Bay of Plenty and Hawke’s Bay homes without power.
Noll said 2017’s high rainfall events could be explained by a mix-andmatch set-up of temperatures across the Pacific. While the sea surface temperatures near Peru had been warmed by a El Nino Costero — a variation of the normal climate system — those in the Central Pacific were cooler than average, while the Western Pacific remained warmer than average.
“So across the Pacific, we had warm, cool, warm — and that difference may have contributed to our wetness early in the season.”
Now, a strong La Nina system had brought dominant high-pressure systems across much of the country, with abnormally high sea surface temperatures also cranking up the late-year heat.
“Our anomalies for November and December are going to be significant driven by the very warm sea temperatures that we have now surrounding New Zealand, and basically engulfing it. So it’s not going to be colder than average when your sea surface temperatures are 2C-4C above average — that’s just something that will never happen.”
While it was difficult to factor in what background effects climate change might have had, these were expected to become more significant as the planet warmed.
But globally, a clear pattern was emerging: 16 of the world’s 17 hottest years have occurred since the turn of the century.