New climate change projections for Canterbury
We are committed to helping our communities to understand and be resilient to natural hazards risk, including climate change, and we asked the National Institute of Water and Atmospheric Research (NIWA), to analyse projected climate changes for our region.
Published in 2020, NIWA's report (below) looks at how aspects of our climate such as temperature, precipitation (rain, snow, drought potential), wind and sea levels might change between now and 2100. It is based on global climate model simulations from the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment, scaled down for New Zealand, with a focus on Canterbury.
This is a technical report (not for the faint-hearted!) but it is the most detailed information we have. Each chapter has a helpful summary, and key projections are set out below.
The projections in this report, and other relevant science, have been summarised on the It’s time, Canterbury website.
View NIWA report: Climate change projections for the Canterbury Region (PDF File, 16.5MB)
Understanding emissions 'scenarios'
A little bit of technical knowledge goes a long way. Remember the thickness of the blanket?
Assessing future climate change due to human activity is difficult, because projections depend on greenhouse gas concentrations, which in turn depend on how we respond as a society. Climate scientists have dealt with those dependencies by developing different possible 'scenarios', based on different amounts of greenhouse gases in the atmosphere. These scenarios are called Representative Concentrations Pathways (RCPs), abbreviated as RCP2.6, RCP4.5, RP6.0, and RCP8.5. RCP8.5 is the highest level.
The NIWA report looks at two scenarios: RCP4.5 (which could be realistic if immediate global action is taken towards mitigating climate change) and RCP8.5 (sometimes called the 'business-as-usual', where emissions continue at current rates).
To keep it simple here, we've described these two scenarios as whether we cut emissions, or if we don’t.
Projections for Canterbury
- Increase with time and greenhouse gas concentrations.
- By 2040, annual mean temperature up 0.5 to 1.5°C.
- By 2090, up 0.5 to 2°C (if we cut emissions) or up 1.5 to 3.5°C (if we don't).
- By 2040, annual mean maximum temperature up 0.5 to 2°C.
- By 2090, up 1 to 3°C (if we cut emissions) and up 2 to 5°C (if we don't).
- By 2090, western Canterbury's alpine and sub-alpine areas could be 5 to 6°C warmer in spring and summer (if we don't).
- By 2040, annual mean minimum temperature up zero to 1°C.
- By 2090, up 0.5 to 1.5°C (if we cut emissions) and up 1 to 2.5°C (if we don't).
- The difference between a day's high and low increases with time and greenhouse gas concentrations.
- By 2090, expect 20 to 60 more hot days in most of Canterbury (if we don't cut emissions).
- Inland areas feel it the most, particularly the southern Mackenzie Basin, which could have 60 to 85 more hot days.
- Most of these hot days would happen in summer.
- Our warmer season could get longer in relatively low-elevation areas, with 5 to 10 more hot days in autumn and spring.
- Expect fewer frost days throughout the region.
- Inland areas and higher elevations warm the most, with 10 to 30 fewer annual frost days by 2040, and 20 to 50 fewer by 2090.
- The frost season (the time between a year's first and last frost) will likely get shorter.
- Most of the region can expect small changes in annual rainfall, up or down 5%.
- By 2040, autumn might be dryer in the Mackenzie Basin, with up to 10% less rain.
- By 2090, winters could be wetter in many eastern, western and southern parts of the region, with 15 to 40% more rain.
- By 2090, Banks Peninsula and many inland areas might get 5 to 15% less rain (if we don't cut emissions).
- Expect fewer snow days everywhere, especially in the mountains.
- Expect more potential for drought across most of Canterbury.
- Annual mean wind speeds up slightly, by nil to 5%.
- By 2090, winter and spring could be windier (up 5 to15%, if we don’t cut emissions).
- That seasonal change might be more keenly felt in inland areas north and west of Rangiora (up 15 to 25%).
- Sea level rise projections for Canterbury are the same as for New Zealand.
- Up by 0.4m in the next 50 years and up 0.6 to 0.7m in 100 years (if we cut emissions).
- Up 0.5m in 50 years and up 1.2 metres in 100 years (if we don't).
- High tides get higher. At 0.65 metres of sea level rise, every high tide is above the spring tide mark (compared to 10% now).