Climate change projections for the Bay of Plenty region

Map of Bay of Plenty region.

This page provides an overview of how the climate in the Bay of Plenty region is likely to change into the future and what implications this has for the region.

Projections of climate change depend on future greenhouse gas emissions, which are uncertain. There are four main global emissions scenarios ranging from low to high greenhouse gas concentrations. This page presents regional projections as a range of values from a low emissions to a high emissions future.

The projected changes are calculated for 2031–2050 (referred to as 2040) and 2081–2100 (2090) compared to the climate of 1986–2005 (1995).

Temperature

Compared to 1995, temperatures are likely to be 0.7˚C to 1.1˚C warmer by 2040 and 0.7˚C to 3.1˚C warmer by 2090.

By 2090, the Bay of Plenty is projected to have from 10 to 59 extra days per year when maximum temperatures exceed 25˚C, with up to 15 fewer frosts per year.

Rainfall

Rainfall will vary locally within the region. The largest changes in rainfall will be for particular seasons rather than annually, with spring rainfall projected to decrease by 1 per cent to 11 per cent in Tauranga by 2090.

There is large natural variability in extreme rainfall frequency in the Bay of Plenty from year to year and decade to decade. According to the most recent projections, the Bay of Plenty is not expected to experience a significant change in the frequency of extreme rainy days as a result of climate change.

Wind

The frequency of extremely windy days in the Bay of Plenty by 2090 is not likely to change significantly. It is possible the region may experience more north-easterly winds during summer and more westerly winds during winter.

Storms

Future changes in the frequency of storms are likely to be small compared to natural inter-annual variability. Some increase in storm intensity, local wind extremes and thunderstorms is likely to occur.

The frequency of ex-tropical cyclones is projected to either decrease or remain unchanged over the 21st century; however the ex-tropical cyclones will likely be stronger and cause more damage as a result of heavy rain and strong winds. 

Sea-level rise

New Zealand tide records show an average rise in relative mean sea level of 1.7 mm per year over the 20th century. Globally, the rate of rise has increased, and further rise is expected in the future. 

The Ministry for the Environment provides guidance on coastal hazards and climate change, including recommendations for sea level rise, see Preparing for coastal change: A guide for local government in New Zealand.  An updated edition will be published in late 2016.

Impacts by season

By 2090, the region could expect*:

Spring

  • 0.6°C to 2.8°C temperature rise
  • 1 to 11 per cent less rainfall in Tauranga

Summer

  • 0.7°C to 3.3°C temperature rise
  • 1 to 7 per cent more rainfall in Tauranga

Autumn

  • 0.7°C to 3.2°C temperature rise
  • 2 to 4 per cent more rainfall in Tauranga

Winter

  • 0.7°C to 3.1°C temperature rise
  • 1 per cent less to 2 per cent more rainfall in Tauranga

*Projected changes are relative to 1995 levels. The values provided capture the range across all scenarios. They are based on scenario estimates and should not be taken as definitive. For more information, see the full report on climate projections.

What could this mean for the Bay of Plenty?

Heavy rain – The capacity of stormwater systems may be exceeded more frequently due to heavy rainfall events which could lead to surface flooding. River flooding and hill country erosion events may also become more frequent. 

Coastal hazards – Coastal roads and infrastructure will face increased risk from coastal erosion and inundation, increased storminess and sea-level rise.

Drought – By 2090, the time spent in drought ranges from minimal change through to more than double depending on the climate model and emissions scenario considered. More frequent droughts are likely to lead to water shortages, increased demand for irrigation and increased risk of wild fires. Droughts are likely to increase in both intensity and duration.

Lakes – Higher temperatures and changes in rainfall are likely to result in higher lake levels, on average, in western and central parts of New Zealand, and lower levels in some eastern areas such as the Rotorua Lakes. Warmer water temperatures could lead to more algal blooms, a reduced range of trout and the spread of pest species like carp.

Agriculture – Warmer temperatures, a longer growing season and fewer frosts could provide opportunities to grow new crops. Farmers might also benefit from faster growth of pasture and better crop-growing conditions. However, these benefits may be limited by negative effects of climate change such as prolonged drought and greater frequency and intensity of storms. Warmer winters could affect kiwifruit production, making some varieties uneconomic in warmer parts of the region.

The Ministry for Primary Industries website and associated website Climate Cloud have more information on the regional impacts of climate change on agriculture.

Biosecurity – Warmer, wetter conditions could increase the risk of invasive pests and weeds.

Disease – There may be an increase in the occurrence of summer water-borne and food-borne diseases, such as Salmonella. There could also be an increased risk from some vector-borne diseases such as Dengue Fever and Ross River Virus.

Find out more

Bay of Plenty Regional Council’s climate change information [Bay of Plenty Regional Council website]

Reviewed:
30/06/16