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Impacts: Aotearoa’s changing climate

Image: Marcus Kauffman

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Aotearoa’s changing climate

Summary

This century, climate change will alter New Zealand’s natural water cycle significantly. It will change how much rain and snow we receive, and at what time of year. It will change how much water is stored in the soil, snow, glaciers and aquifers. It will change how much water evaporates back to the atmosphere and how much flows through streams and rivers to the coast. And it will change the severity of droughts, floods and power shortages. – Deep South

Two-thirds of New Zealanders live in areas prone to flooding and rising sea levels – NZ Statistics, 2023

The number of people exposed to these hazards will increase as the climate changes. – p53 Draft Adaptation Plan for New Zealand, April 2022 (The final National Adaptation Plan was released August 2022)

This Southern Ocean warming and its associated impacts are effectively irreversible on human time scales, because it takes millennia for heat trapped deep in the ocean to be released back into the atmosphere. – Huguenin et al, 2022

The condensation of water vapour to make rain droplets releases heat. This, in turn, can fuel stronger convection in thunderstorms, which can then dump substantially more rain. This means that the intensity of extreme rainfall could increase by much more than 7% per degree of warming. What we’re seeing is that thunderstorms can likely dump about double or triple that rate – around 14–21% more rain for each degree of warming. – Dowdy et al, May 2024

The globe is very likely to blow through the 1.5°C warming threshold, and may well go through 2°C warming as well. For us, that will mean more droughts, more floods, more coastal flooding, among many other impacts. Marine heatwaves that we have experienced in recent years will become the average conditions before the end of the century. – Prof. James Renwick, October 2023
 

  Impacts

Other sections

Home > Climate wiki > Impacts

Summary

This century, climate change will alter New Zealand’s natural water cycle significantly. It will change how much rain and snow we receive, and at what time of year. It will change how much water is stored in the soil, snow, glaciers and aquifers. It will change how much water evaporates back to the atmosphere and how much flows through streams and rivers to the coast. And it will change the severity of droughts, floods and power shortages. – Deep South

Two-thirds of New Zealanders live in areas prone to flooding and rising sea levels – NZ Statistics, 2023

The number of people exposed to these hazards will increase as the climate changes. – p53 Draft Adaptation Plan for New Zealand, April 2022 (The final National Adaptation Plan was released August 2022)

This Southern Ocean warming and its associated impacts are effectively irreversible on human time scales, because it takes millennia for heat trapped deep in the ocean to be released back into the atmosphere.”- Huguenin et al, 2022

The condensation of water vapour to make rain droplets releases heat. This, in turn, can fuel stronger convection in thunderstorms, which can then dump substantially more rain. This means that the intensity of extreme rainfall could increase by much more than 7% per degree of warming. What we’re seeing is that thunderstorms can likely dump about double or triple that rate – around 14–21% more rain for each degree of warming.“– Dowdy et al, May 2024

The globe is very likely to blow through the 1.5°C warming threshold, and may well go through 2°C warming as well. For us, that will mean more droughts, more floods, more coastal flooding, among many other impacts. Marine heatwaves that we have experienced in recent years will become the average conditions before the end of the century. – Prof. James Renwick, October 2023
 

* The final National Adaptation Plan was released August 2022.

Why the Earth’s climate is changing

Video 1 explains how greenhouse gases work. The atmosphere can hold ~7% more moisture for every 1°C warming, and the atmosphere already is more than 1.5°C warmer than it was in 1850.
 
Fig. 1: Average temperatures exceededd 1.5°C in mid 2023 and climbed higher throughout the rest of the year. In 2024, they have exceeded 1.5°C every month except June. Image: Copernicus
Fig. 1: Average temperatures exceededd 1.5°C in mid 2023 and climbed higher throughout the rest of the year. In 2024, they have exceeded 1.5°C every month except June. Image: Copernicus
Video 1: How greenhouse gases work to maintain or change the climate.
Fig. 3: Based on IPCC AR4 5.2.2.3 for the period 1993-2013. (Image: Skeptical Science).
Fig. 3: Based on IPCC AR4 5.2.2.3 for the period 1993-2013. (Image: Skeptical Science).

Climate outlook for Aotearoa

The following is from the Ministry for the Environment: First national climate change risk assessment for New Zealand (NCCA) August 2020, page 8. (Note that temperatures are now exceeding 1.5C).

“New Zealand’s climate is warming, sea levels are rising, and extreme weather events are becoming more frequent and severe.The National Institute of Water and Atmospheric Research(NIWA) developed the climate change projections used for this risk assessment after the release of the IPCC Fifth Assessment Report. They include the following trends:

  • In the last 100 years,our climate has warmed by 1°C. If global emissions remain high, temperatures will increase by a further 1.0°C by 2040 and 3.0°C by 2090.
  • In the last 60 years, sea levels have risen by 2.44 mm per year. If global emissions remain high, sea levels will increase by a further 0.21m by 2040 and 0.67m by 2090.
  • Extreme weather events such as storms, heatwaves and heavy rainfall are likely to be more frequent and intense. Large increases in extreme rainfall are expected everywhere in the country, particularly in Northland due to a projected increase in ex-tropical cyclones.
  • The number of frost and snow days are projected to decrease, and dry days to increase for much of the North Islandand for some parts of the South Island.
  • Drought is predicted to increase in frequency and severity, particularly along the eastern side of the Southern Alps.
  • Increased north-easterly airflows are projected in summer and stronger westerlies in winter, the latter particularly in the south of the South Island.
  • Wildfire risk is predicted to increase in many areas towards the end of the century, due to higher temperatures and wind speeds, and decreased rainfall and relative humidity.”

Climate outlook for biodiversity

The IPCC Sixth Assessment Report: Impacts, Adaptation and Vulnerability, has placed nature at the forefront of its projections, recognising the critical life-supporting role of biodiversity in human health and well being as well as adapting to the impacts of climate change. The report paints a dire picture.

Fig. 4: Just a half a degree of warming more than triples the loss of biodiversity in some areas (Image: Carbon Brief).
Fig. 4: Just a half a degree of warming more than triples the loss of biodiversity in some areas (Image: Carbon Brief).

The future?

The following is from the Ministry for the Environment: First national climate change risk assessment for New Zealand (NCCA) August 2020, page 8:

“We tend to have this idea that our climate is gradually warming and these types of impacts will be gradual…but the Earth system doesn’t work like that. There’s no reason to expect that a gradual increase in temperature will contribute to a gradual increase in the types of fires we’re having to fight.” – Professor Nerilie Abram, ANU

As the climate warms, the weather system in the Indian Ocean, the Indian Dipole (the Pacific ‘sister’ of El Niño/La Niña) is expected see more strong “positive” events similar to the 2019-20 Australian drought and bushfires that dumped ash on our glaciers, hastening their melting.

The current climate change projections for Canterbury are based on the 2013 IPCC Assessment Report.  Real-world events, the latest research and satellite data, and the latest (February 2022) IPCC Report show that we have outpaced several of these climate projections. The National climate change risk assessment for New Zealand report uses the RCP8.5 ‘Representative Concentration Pathways (RCPs) worst case scenario. It also states that:

“More extreme scenarios are possible, and the sensitivity of the climate system remains uncertain.”

An Adaptation Plan for New Zealand was released August 2022.

Fig. 5: To see an interactive map, click on the image. This will take you to the IPCC website. This screengrab is an example of how you can enter specific information for regions (in this example, New Zealand/ land only) and check the projected temperature changes over time, based on different models and pathways.
Fig. 5: To see an interactive map, click on the image. This will take you to the IPCC website. This screengrab is an example of how you can enter specific information for regions (in this example, New Zealand/ land only) and check the projected temperature changes over time, based on different models and pathways.

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