What is Climate Change?
The Earth's climate is changing. Over the last 100 years, this process of change has sped up. Today, changes in our climate mean we are rapidly moving towards a warmer environment. The warming is already having an influence on our living environment.
Scientists believe the warming is caused by human activities. During the last 50 to 100 years, increasing industrialisation and human activity (such as burning fossil fuels for transportation and electricity generation) have begun to affect the proportion of greenhouse gases (e.g. CO², CH4, N²O) in the Earth’s atmosphere. Greenhouse gases act in the same way as a greenhouse – trapping in the heat. The increased amount of greenhouse gases in our atmosphere causes the Earth to heat up at a fast rate.
Planet Earth is a dynamic place. Climate change effects vary in different locations. Scientists have developed a number of scenarios for future warming. These scenarios show different degrees of warming depending on what we do collectively with global greenhouse gas emissions. These scenarios range from fossil-fuel intensive rapid global economic growth to a service and economic based economy. Nevertheless, even in the most optimistic scenario the world should expect some degree of warming.
For more information, see www.climatechange.govt.nz
Adapting to the effects of Climate Change
Adapting to climate change means preparing our communities, industries and infrastructure for the effects of these changes. Adapting to climate change can help minimise the risks we face as well as maximise the opportunities arise from our changing climate.
So, what has been the Bay of Plenty's climate?
This region has a climate with warm humid summers and mild winters. Typical summer daytime maximum air temperatures range from 22°C to 26°C, but seldom exceed 30°C. Winter daytime maximum air temperatures range from 9°C to 16°C. The sea influences air temperatures considerably in the coastal areas and sea surface temperatures on the east coast are the warmest in New Zealand. The region has one of the sunniest climates in the country. Annual sunshine hours average about 2000 in many areas. Coastal areas, for example from Tauranga to Whakatane, are much sunnier with at least 2200 hours, and dry spells are common.
Southwest winds prevail for much of the year. Sea breezes often occur on warm summer days. Winter usually has more rain and is the most unsettled time of year. In summer and autumn, storms of tropical origin may bring high winds and heavy rainfall from the east or northeast.
Source: New Zealand Climate Change Office, Ministry for the Environment |
For more information on climate change and what we can do about it, see the website: www.climatechange.govt.nz, email info@climatechange.govt.nz or phone 0800 WARMING.
Observed Changes
- Since the early 1900s, average temperatures have risen by about 1˚C. The Bay of Plenty recorded very high temperatures in the 1990s.
- Between 1951 to 2000, the seasonal temperatures along the coast increased by up to 0.2˚C every 10 years. In coastal places, Tauranga for instance, the number of frosts has decreased significantly.
- The record shows that cold nights have significantly warmed since 1940 (an increase of 0.3˚C every 10 years).
- Rainfall and temperature changes differ according to location and topography. Since 1950, there has been less rain in north-eastern New Zealand.
- There have been fewer storm events, partly due to natural climatic variation during this period.
- Sea level in the Australia and New Zealand region has risen about 7 cm since 1950.
What does climate change mean for the Bay of Plenty?
A snapshot of the 2030s
Temperature:
It is virtually certain that the climate will be warmer, especially in winter. For the Bay of Plenty, winters will be on average warmer by 0.8 °C compared with the period 1970 – 2000, with fewer cold days. Other seasons will be about 0.7 °C warmer. This means that the average temperature in coastal Bay of Plenty will be similar to conditions in Kaitaia today.
Map of projected seasonal midpoint temperature in 2030 (186KB, pdf)
Rainfall:
In general, the change varies with seasons and geography. There will be drier springs and summers and slightly wetter winters. Coastal areas are likely to be drier.
Projected seasonal rainfall changes range from -7.5% to +7.9%, depending on location and season.
- The Rotorua Lakes could expect 4.5% (90 mm) more rain in winter.
- The Manawahe area could experience 7.5% (135 mm) less rain in spring.
Map of projected seasonal midpoint rainfall in 2030 (172KB, pdf)
A snaphot of the 2080s
Temperature:
In the 2080s, winters will be warmer by more than 2.3 °C compared to the period 1970 to 2000, while other seasons will be warmer by 1.8 °C.
Map of projected seasonal midpoint temperature in 2080 (191KB, pdf)
Rainfall:
The Rotorua, Rotoehu, Rotoma and Okataina areas should be prepared for 8% (160 mm) more rain in winter in the 2080s. Some parts of the coastal area (such as Katikati, Te Puke, Maketu and Waihau Bay) will experience drier springs with spring rainfall reduced by as much as 18% (250 mm).
Map of projected seasonal midpoint rainfall in 2080 (149KB, pdf)
What are we preparing for?
Extreme rainfall events:
While there is a large variability in extreme rainfall frequency in this region, various modelling studies suggest that heavy rainfall events will occur more frequently in New Zealand over the coming century. It is possible that long-term trends in extreme rainfall will not be noticeable in the Bay of Plenty region until the latter half of the 21st century. Over the next 50 years, changes are more likely to be caused by natural climatic variability than greenhouse gases.
Drought:
Droughts that currently occur about once every 20 years could happen once every 5 to 10 years. There will be drier average conditions, particularly in coastal areas and in spring. The projections are for a decrease in spring rainfall and an increase in winter rainfall. Rainfall changes are more uncertain than temperature changes.
Storm events:
An increase in severe wind risk may occur, but there is insufficient information for quantitative predictions. Over the next 70 to 100 years, ex-tropical cyclones might be slightly less likely to reach NZ, but if they do, their impact might be greater than now.
Wind:
In the next 50 years, the mean westerly wind component across New Zealand is expected to increase by 10% of its current value. Increasing westerlies are one reason for a drying trend in the Bay of Plenty. Strong winds are expected to be more frequent with the warmer climate together with an increase in the frequency and intensity of low-pressure systems.
Sea Level:
Sea level is estimated to rise by 37–55 cm over the next 70 to 100 years. To plan for the coastal environment, we’ve adopted a projected increase of 49 cm by 2100.
What are the predicted changes and their impacts?
Sea-level rise
- Inundation of low-lying coastal areas
- Accelerated and more extensive coastal erosion
- Increased drainage costs, which may become unsustainable in some low-lying places
- Salt-water intrusion into freshwater sources
More frequent and intense rainfall events
- Increased flood risk
- Increased erosion risk and landslides
- Increased threats to infrastructure
Drier average conditions, particularly in coastal areas and in spring, more dry days (especially in spring)
- Water security problems could lead to irrigated agriculture in some places becoming vulnerable
- Drier average conditions and higher temperatures will lead to increased drought risk
Higher temperatures, less cold days (particularly in winter)
- A longer growing season
- Increased biosecurity threats throughout the region
- Long-term impacts on primary industry, such as spread of sub-tropical pasture species and insufficient chilling for Hayward kiwifruit
- Reduced frequency of frost inland and at higher elevations
- Less cold-stress is likely to reduce lamb mortality
People
Climate trends in recent decades may already be affecting the health of New Zealanders, but any such effects are difficult to demonstrate unequivocally because it is often difficult to separate the effect of changes in climate from the effects of changes in other social and environmental conditions. The impact of climate change depends on the extent and rate of warming, and on how well individuals and society can adapt. A study commissioned by the Ministry for the Environment shows that climate change can affect human health both directly (temperature extremes and heavy rainfall) and indirectly (water supply, pollen causing allergy, ozone depletion, infectious diseases carried by animals or insects, and stress).
Economy
Changes in climate are likely to influence primary industries as production is often influenced by climate conditions. The Bay of Plenty’s primary production (agriculture, forestry and fishing industry) covers 45% of the land and involves over 10% of its labour force. On the other hand, there may be economic opportunities through the introduction of new commercial crops that is more suitable for the coming climate.
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