Climate Change Commission head Rodd Carr discusses climate change reduction targets with student activists in Christchurch. Video / Frank Film
New Zealand’s future under climate change is likely to be even warmer – and drier – than scientists previously forecast, fresh projections show.
The new data, just released in an interactive national map, offers the most comprehensive picture yet of how the country’s climate will be transformed this century.
Depending on how quickly and effectively the world moved to cut emissions, the Niwa-led modelling showed New Zealand’s average temperature would rise by between 0.8C and 3C by 2090.
In most regions, that’d also come with a sizeable jump in the number of extra-hot days, where the maximum temperature rose above 25C.
In Auckland, that occurred around 20 days of the year over the 1995-2014 period, which the new modelling used as a baseline to compare against.
According to the latest mid-range projections, that could be happening on a dozen more days by 2040; 24 more days by 2060; and 48 more days by 2099.
Along with that, the city’s average summer temperature could grow up to 1.7C warmer by 2050 and up to 3.6C warmer by 2090 – at which point Auckland would have also experienced a slight drop in annual rainfall and a slight increase in dry days.
Wellington was projected to become slightly wetter by 2090 – with the greatest change coming over summer (an increase in seasonal rainfall of between 1.7% and 10.6%) - but also warmer (0.7C to 2.8C).
In Christchurch, there could be between 4.6 and 46.6 more hot days by 2090 – while average summer temperatures could be 0.9C to 3.3C warmer by century’s end.
Other 2090 projections for main centres included a jump of between 9.5 and 77.8 hot days in Hamilton; a 9.8% to 18.2% drop in annual rainfall in Tauranga; and an increase of 1.2 to 42.7 more hot days in Dunedin.
More widely, the projections indicated lower annual rainfall across the North Island, especially in the north and east, but more in the west and the south of the South Island.
In Westland, one of New Zealand’s rainiest regions, winter rainfall could increase by between 1.7% and 24.7% by 2090, compared with the baseline period.
The new data can be searched on an online map.
In Hastings, meanwhile, there could be between two and 10 more dry days, with less than a millimetre of rainfall, by 2090 – and 0.9 to 71.9 hot days.
Niwa climate scientist Dr Andrew Tait said the overall trends in the projections were broadly in line with earlier modelling: that included across-the-board warming, fewer frosts, dry areas gradually becoming drier and wet areas growing wetter.
But the new data also showed “subtle” shifts in which future average temperatures were slightly warmer – and most regions slightly drier – than what had been previously forecast.
The projections were based on the latest suite of global climate models and emission scenarios used by the UN’s Intergovernmental Panel on Climate Change (IPCC).
“Generally speaking, these projections are predicting a higher rate of warming than what we’ve seen before.”
Tait described the new projections as “foundational” data – on which future work focused on everything from wildfire and storm risk to water security and pasture productivity would be based.
Already, people could use the data to explore future shifts in temperature, rainfall and wind for every 5km square of New Zealand, making it particularly useful for groups like iwi, councils and primary producers.
“Making these projections available means everyone can access the data and understand what climate change might mean for their community,” said the Ministry for the Environment’s deputy secretary of strategy stewardship and performance, Natasha Lewis.
“This is an important step in improving access to climate information.”
Tait added that, along with gradual climate shifts, Kiwis could also expect associated impacts like more intense storms and higher sea levels.
Earlier this week, Niwa reported climate change had added about 10% more rainfall to last year’s ex-tropical Cyclone Gabrielle, which fell during its most intense stage.
As well, Treasury officials announced an 80% chance of another Gabrielle-scale system hitting New Zealand within the next 50 years.
Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.
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