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Appendix: Climate change projections for New Zealand

 

Climate change projections for New Zealand in table 3 were produced by NIWA following the release of the IPCC Fifth Assessment Report. Projections for ocean acidification, ocean warming, and sea-level rise come from IPCC (2013; 2014a). For more projections and scenarios see the Ministry for the Environment’s climate change projections for New Zealand and NIWA’s climate change scenarios for New Zealand.

Table 3   Magnitude and variation of climate-related changes for New Zealand, data to 2016 and projections

Climate variable

Description of projected change

Timeframe of change

Our data to 2016

Projected changes (compared
with 1995) by:

2040

2090

Average temperature

Warming greatest at higher elevations and during summer/autumn

Warming peaks, then declines slightly during the 21st century only under low carbon projections

Average land surface temperature increased by 1°C since 1909

+0.7°C to +1.0°C

+0.7°C to +3.0°C

2110: +0.7°C to +3.7°C

Frost days

Decrease in frost days (0°C or lower)

Decline in frost days greatest in coldest regions

Reduced frequency of frost days at 10 of 30 locations, increased frequency at 1 location; earliest data 1972

30% to 50% decrease

30% to 90% decrease

Warm days

Increase in warm days (maximum temperature of 25°C or higher)

Increase in warm days at 8 of 30 locations, decrease at one location; earliest data 1972

40% to 100% increase

40% to 300% increase

Average rainfall

Varies around the country and with season

Annual pattern of increases in west and south of New Zealand and decreases in north and east

Seasonal spring decrease in 5 upper North Island locations; seasonal spring increase in 1 site in south of South Island and 2 sites in southwest of North Island; earliest data 1960

Substantial variation around the country, increasing in magnitude with increasing emissions

Not available

Extreme rainfall

Increased extreme daily rainfall, especially where mean rainfall increases, such as on the West Coast

Strongest increases in western regions and in south of the South Island

Decrease in extremes in parts of north and east of the North Island

Increase in annual maximum one-day rainfall at 2 eastern South Island locations and decrease at 4 North Island locations; earliest data 1960

Not available

More than 20% increase in 99th percentile of daily rainfall in southwest of South Island (high emissions scenario)

Snow and ice

Decreases

Large decreases confined to high altitude or southern regions of the South Island

Glaciers lost an estimated 25% in ice volume (about 13.3 cubic kilometres); since 1977

Not available

Snow days per year reduce by 30 days or more (high emissions scenario)

Globally, loss of many glaciers (high emissions scenario) (IPCC, 2014a)

Drought

Increase in severity and frequency in most areas, except for Taranaki-Manawatu, West Coast and Southland

Increases most marked in already dry areas

Soils became drier at 7 of 30 sites and wetter at 1 site; since 1972

Not available

More than 20% increase in drought magnitude per year (July–June) on average

Extreme wind speeds

Most robust increases occur in southern half of the North Island and throughout the South Island

Decreases in the North Island from Northland to Bay of Plenty

Decreased extreme wind speeds at nearly one-third of sites; earliest data 1972

Up to 10% or more in parts of the country

Ocean warming (IPCC, 2013)

Globally, progressive increase.

At greater depth the warming will be most pronounced for the Southern Ocean (IPCC, 2013)

Our data (satellite data from 1993) shows no trend

Long-term data shows warming of 0.71°C from 1909–2009 (Mullan et al, 2010)

Best estimates of global ocean warming by 2100 are about 0.6°C (low emissions scenario) to 2.0°C (high emissions scenario) in the top 100 metres of the sea (compared with 1986–2005 climate normal) (IPCC, 2013)

Ocean acidification (lowering pH) (IPCC, 2014a)

Globally, decreasing pH (increasing acidity) to 2100 under all emissions scenarios (IPCC, 2014a)

Decreased pH (increased acidity) of subantarctic waters since 1998

Globally a pH decline ranging from 0.06–0.07 (low emissions scenario) to 0.30–0.32 (high emissions scenario) by 2100 (IPCC, 2014a)

Sea level rise (IPCC, 2013)

Globally, progressive increase faster than over the last century and continuing for many centuries

Relative sea-level rise will vary at different locations around New Zealand

Rates of 1.4 to 2.2 mm each year depending on location (earliest data as far back as 1891 for some sites; data to 2015 for all sites)

Global projections (relative to 1986-2005):

  • 2060: 0.2 m to 0.4 m rise
  • 2100: 0.3 m to 1.0 m rise (IPCC, 2013)

The collapse of parts of the Antarctic ice sheets could substantially increase the upper end of this range

New Zealand’s offshore sea-level rise may be up to 0.05 m more than global average sea level rise (Ackerley et al, 2013)