Impacts: Aotearoa’s changing climate
Image: Marcus Kauffman
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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 oceans have absorbed ~93% of warming and are heating up 40% faster than previously estimated.
- The Southern Ocean, which plays a major role in Aotearoa’s climate, is almost entirely responsible for ‘uptaking almost all the planet’s ocean warming‘.
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
In the Southern Hemisphere climate models consistently predict an almost year-round poleward shift in mid-latitude westerly winds as a consequence of global warming. This poleward shift is most notable in the cool season, April–September. – Speer et al 2022
- The atmosphere holds
~ 7% more water for every 1°C warming; resulting in more intense precipitation, and more heat = more energy, winds are getting stronger. But:
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
- Extreme weather and increased evapotranspiration is leading to plant stress, damaging ecosystems and agriculture (food production).
- Reducing emissions won’t reverse warming or return us to a ‘normal’ climate as there’s a long lag time between emitting greenhouse gases and their effect (see ‘the last time there was this much carbon dioxide in the atmosphere‘).
- This is increasingly costly for all of us in a multitude of ways, from marine heatwaves that supercharge storms to drought, floods (rain and/or rivers), rising sea levels, ocean acidification, and loss of critical ecosystem services we need to survive.
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Some incoming radiation from the sun is reflected back into space due to the albedo effect of the cryosphere (ice caps, permafrost, glaciers) and atmospheric aerosols much of which, paradoxically, come from burning fossil fuels. About 89% of the retained excess heat is being absorbed by the oceans. The land takes up ~6%, the cryosphere absorbs ~4%—which is why it’s rapidly melting—and the remaining 1% is in the atmosphere.
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Temperature anomalies by Latitude for the first three months of 2026. Surface temperatures in the Southern Hemisphere were slightly more than 1°C higher compared to the period 1961-1980. This is because our hemisphere has less land and more ocean which takes up more heat. Despite our recent weather bombs, we’re experiencing less extreme weather and temperatures than the global average. Credit: Dr. Zack Labe Climate Central
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Click the image above to be taken to the online portal. It contains multiple variables that allow you to explore how the climate is projected to change compared to historical base periods. Zoom in to explore what our future climate may look like in your area, based on the data used is the average (mean) of the values produced by each of the six climate models (Coupled Model Intercomparison Project Phase 6 or CMIP6). NOTE: these projections are based on the modelling of available data. THEY ARE NOT PREDICTIONS. They are guides that will change as more data comes to hand. They do not adequately capture extreme events.
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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.
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Just a half a degree of warming more than triples the loss of biodiversity in some areas; Image: Carbon Brief
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Clean ice and snow have a very high albedo, that is, they reflect up to 90% of solar radiation back into space The ocean is much darker, so it has a very low albedo, reflecting only about 6% of the incoming solar radiation and absorbing the other 94%, warming it much faster than the snow and ice (Fig. 4).
