The speed and scale of changes to New Zealand’s climate, and the subsequent risks that we face from climate change, depend on what the global community does about greenhouse gas emissions and how the climate system responds to those emissions.
To assist decision-making in the face of uncertainty about future global emissions, scientists use models to project climate change under different concentration pathways, associated with low to high emissions during the 21st century. Over 40 climate models have been developed by different research agencies around the world, and each simulation has different strengths and weaknesses for particular regions and climate properties. In general, they show impressive skill in simulating details of the climate system and continue to improve as we learn more. Observations and qualitative comparisons supported by models provide important evidence when assessing how human activities affect climate change.
Figure 15 shows the distribution of a range of projected climate-related changes across New Zealand. More detailed information on these projections is provided in Appendix: Climate change projections for New Zealand.
The size of the risks New Zealand faces from future climate change depends on the extent to which countries reduce their greenhouse gas emissions (mitigation). The faster and larger the reduction, the lower the risk of severe and enduring impacts on the natural environment and people’s lives.
From another world view, our future climate may depend on a much broader response from global citizens than lowering emissions alone. At Ministry for the Environment consultations with hapū and iwi in 2007, Māori elders described the changing climate as an imbalance in the natural order that resulted from people becoming distanced from their relationships with each other, the environment, and their ancestors.
Global emission scenarios and climate risk
Understanding climate risks from a global perspective is important because New Zealand is both vulnerable to some of these risks and cannot be isolated from impacts of global warming experienced by the rest of the world. Figure 16 shows two possible pathways of greenhouse gas emissions and atmospheric greenhouse gas concentrations with associated global warming and climate-related risks – low and high. High risk, for example, indicates severe, widespread, and irreversible impacts. Many risks will be particularly challenging for the least developed countries and vulnerable communities, given their limited capacity for adapting to change (IPCC, 2014b).
The low-emissions scenario (RCP2.6) would require countries to achieve ambitious reductions in emissions and is likely to result in global warming kept below 2 degrees Celsius above pre-industrial temperatures. The high emissions scenario (RCP8.5) assumes no additional efforts are made to constrain emissions (IPCC, 2014a).
Actions to achieve the low-emissions scenario include capturing carbon during industrial processes and storing it in long-term reservoirs, such as the deep ocean, or enhancing natural processes that increase the removal of carbon from the atmosphere, for example, through afforestation.
Without additional measures to reduce greenhouse gas emissions beyond those already in place today (a high emissions scenario), then global warming by the end of the 21st century is likely to be between 2.6 and 4.8 degrees Celsius (relative to 1986–2005)(see box 7). This magnitude of warming will lead to high to very high global risk of severe, widespread impacts for natural and human systems (IPCC, 2014a), with far-reaching implications for humanity.
This figure shows the distribution of projected climate-related change across New Zealand.
Figure 16 A global perspective on climate-related risks
Source: IPCC, 2014b
Note: The figure on the right shows five integrative reasons for concern about human influence on the climate system. Unique and threatened systems includes ecosystems and cultures, some of which are already at risk from climate change. Extreme weather events includes heat waves, extreme precipitation, and coastal flooding. Distribution of impacts recognises that risks are generally greater for disadvantaged people and communities. Global aggregate impacts includes impacts to Earth’s biodiversity and overall global economy. Large-scale singular events recognises that with increasing warming some physical systems or ecosystems may be at risk of abrupt and irreversible changes. For more detail see IPCC (2014b).
This graph shows a global perspective on climate-related risks.
Box 7 1.5 degrees… 2 degrees… 4 degrees Celsius and beyond
Human civilisation has never experienced global average temperatures 2 degrees Celsius warmer than pre-industrial times. For at least the last 10,000 years, the global average temperature has fluctuated by less than 1 degree Celsius (Marcott et al, 2013). However, without efforts to reduce greenhouse gas emissions and atmospheric concentrations, Earth could warm by more than 4 degrees Celsius – making it warmer than any time since Homo sapiens first appeared.
Scientists have warned that the greater the magnitude of global warming, the greater the risk of severe and pervasive detrimental impacts on humanity and the world’s natural ecosystems (IPCC, 2014a). The difference between 1.5 and 2 degrees warming presents increased risk for some vulnerable ecosystems and parts of the world, for example, low-lying Pacific islands.
The 2015 Paris Agreement is an international agreement instigated under the United Nations Framework Convention on Climate Change. The Agreement seeks to hold the increase in the global average temperature to well below 2 degrees Celsius above pre‑industrial levels and to pursue efforts to limit the temperature increase to 1.5 degrees Celsius. This would limit the amount of warming and other climate changes New Zealand will experience.
Whether the global community can keep warming below 2 degrees Celsius is one of the biggest uncertainties in climate predictions. While the Paris Agreement requires parties to take stock of progress and increase the ambition of their emissions reduction targets, some scientists think it is highly unlikely that we can keep warming below 2 degrees Celsius because countries’ current pledges to reduce emissions are insufficient (Rogelj et al, 2016). Meeting this goal will require substantial and sustained global reductions of greenhouse gas emissions (IPCC, 2014a). Any delay in reducing emissions will increase the size of the emission reductions required in the future.
Adaptation and vulnerabilities
Alongside global mitigation, the future impacts of climate change on New Zealand also depend on the extent to which New Zealand communities, businesses, and governments are able to adjust to a changing climate (adaptation). Adaptation includes, for example, local councils’ flood protection and spatial planning measures and the introduction of drought-resistant plant species in agriculture.
For example, after serious flooding in 2005, Tauranga City Council reviewed and upgraded its stormwater services to cope with the large rainfall events that are expected to occur with climate change (Ministry for the Environment, 2008).
Communities with fewer resources and less resilience are more likely to be negatively affected by climate risks such as flooding and extreme weather events. The resilience of New Zealand communities will depend on their location, the adequacy of existing local infrastructure, the resources communities have available to respond and adapt, and the influence of other pressures such as population growth or decline.
Climate change is highly likely to exacerbate existing economic and social disparities for Māori (King et al, 2010); although any impacts will vary widely across different regions, organisations, communities, and groups. Projected impacts are speculative but may include, for example, increased insurance premiums, reduced work opportunities associated with drought, water shortages for isolated rural communities, or flood control and coastal infrastructure that restrict access and Māori customary activities.
Further research on New Zealand’s environmental, economic, and social sensitivity to climate-related impacts is a priority over the next five years (Ministry for the Environment & Department of Conservation, 2017).
Data and research on the impacts and implications of future climate change for Māori are also limited. A series of research programmes and projects is currently underway across the country to help fill these gaps and develop practical tools and knowledge that will strengthen the capacity and capability of iwi, hapū, whānau, and Māori business to deal with the potential consequences of climate change (eg see The Deep South’s Vision Mātauranga).
For a comprehensive discussion of the future impacts and implications of climate change for New Zealand, see:
- IPCC report: Australasia chapter in: Climate Change 2014: Impacts, Adaptation, and Vulnerability
- Royal Society Te Apārangi reports:
- Parliamentary Commissioner for the Environment report: Preparing New Zealand for rising seas: Certainty and uncertainty.