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- Assessing Likely Regional Impacts of Climate Change
- The Australia and New Zealand Chapter of the IPCC Working Group II Report (Impacts, Adaptation and Vulnerability)
- The Regional Climate Model
Quantitative projections of the impacts of climate change over a region such as New Zealand are difficult. This is because of the uncertainties in regional climate change projections, the limited knowledge about sensitivities of some systems (both natural ecosystems and managed agricultural activities) to climate, and the interactions of multiple climatic and non-climatic factors on such systems. Nevertheless, there is a strong demand for advice on regional impacts. Governments want to know the likely impacts in their region in order to make sensible policy decisions regarding greenhouse gas emissions and adapting to climate changes, and as background for negotiations on global agreements (such as protocols to the UN Framework Convention on Climate Change).
The approach typically taken for estimating regional impacts involves combining information from a range of plausible climate scenarios, with knowledge about the sensitivity to climate of various systems and processes. Taking such an approach one can gain at least a qualitative impression of likely regional environmental, economic and social impacts. In 1998 the Intergovernmental Panel on Climate Change (IPCC) produced a Special Report entitled "The Regional Impacts of Climate Change – An Assessment of Vulnerability". This contained a chapter on each of the main regions of the World, including Australasia and Antarctica. In addition, the 2007 IPCC fourth assessment report Working Group II “Impacts, Adaptation and Vulnerability” contains several chapters regarding the impacts of climate change over major regions of the World including Africa, Asia, Australasia, Europe, Latin America, North America, the polar regions and small islands. The Summary for Policymakers of these reports are available from the IPCC website.
The Australia and New Zealand Chapter of the IPCC Working Group II Report (Impacts, Adaptation and Vulnerability)
The Executive Summary of the Australasia chapter of the IPCC 2007 fourth assessment report Working Group II “Impacts, Adaptation and Vulnerability” is provided below. The coordinating lead authors of this chapter were Kevin Hennessy (Australia) and Blair Fitzharris (New Zealand), and the other lead authors were Bryson C. Bates (Australia), Nick Harvey (Australia), Mark Howden (Australia), Lesley Hughes (Australia), Jim Salinger (New Zealand) and Richard Warrick (New Zealand).
Click on the link below for a synthesis report of the key findings of the IPCC 4th Assessment on climate change impacts for New Zealand and the South Pacific.
Literature published since the IPCC Third Assessment Report confirms and extends its main findings (high confidence).
There is more extensive documentation of observed changes to natural systems, major advances in understanding potential future climate changes and impacts, more attention to the role of planned adaptation in reducing vulnerability, and assessments of key risks and benefits.
Regional climate change has occurred (very high confidence).
Since 1950, there has been 0.4 to 0.7°C warming, with more heatwaves, fewer frosts, more rain in north-west Australia and south-west New Zealand, less rain in southern and eastern Australia and north-eastern New Zealand, an increase in the intensity of Australian droughts, and a rise in sea level of about 70 mm.
Australia and New Zealand are already experiencing impacts from recent climate change (high confidence).
These are now evident in increasing stresses on water supply and agriculture, changed natural ecosystems, reduced seasonal snow cover, and glacier shrinkage.
Some adaptation has already occurred in response to observed climate change (high confidence).
Examples come from sectors such as water, natural ecosystems, agriculture, horticulture and coasts. However, ongoing vulnerability to extreme events is demonstrated by substantial economic losses caused by droughts, floods, fire, tropical cyclones and hail.
The climate of the 21st century is virtually certain to be warmer, with changes in extreme events.
Heatwaves and fires are virtually certain to increase in intensity and frequency (high confidence). Floods, landslides, droughts and storm surges are very likely to become more frequent and intense, and snow and frost are very likely to become less frequent (high confidence). Large areas of mainland Australia and eastern New Zealand are likely to have less soil moisture, although western New Zealand is likely to receive more rain (medium confidence).
Potential impacts of climate change are likely to be substantial without further adaptation.
As a result of reduced precipitation and increased evaporation, water security problems are projected to intensify by 2030 in southern and eastern Australia and, in New Zealand, in Northland and some eastern regions (high confidence).
Ongoing coastal development and population growth, in areas such as Cairns and south-east Queensland (Australia) and Northland to Bay of Plenty (New Zealand), are projected to exacerbate risks from sea-level rise and increases in the severity and frequency of storms and coastal flooding by 2050 (high confidence).
Significant loss of biodiversity is projected to occur by 2020 in some ecologically rich sites, including the Great Barrier Reef and Queensland Wet Tropics. Other sites at risk include Kakadu wetlands, south-west Australia, sub-Antarctic islands and alpine areas of both countries (very high confidence).
Risks to major infrastructure are likely to increase. By 2030, design criteria for extreme events are very likely to be exceeded more frequently. Risks include failure of floodplain protection and urban drainage/sewerage, increased storm and fire damage, and more heatwaves, causing more deaths and more blackouts (high confidence).
Production from agriculture and forestry is projected to decline by 2030 over much of southern and eastern Australia, and over parts of eastern New Zealand, due to increased drought and fire. However, in New Zealand, initial benefits to agriculture and forestry are projected in western and southern areas and close to major rivers due to a longer growing season, less frost and increased rainfall (high confidence).
Vulnerability is likely to increase in many sectors, but this depends on adaptive capacity.
Most human systems have considerable adaptive capacity: The region has well-developed economies, extensive scientific and technical capabilities, disaster mitigation strategies, and biosecurity measures. However, there are likely to be considerable cost and institutional constraints to the implementation of adaptation options (high confidence). Some Indigenous communities have low adaptive capacity (medium confidence). Water security and coastal communities are the most vulnerable sectors (high confidence).
Natural systems have limited adaptive capacity: Projected rates of climate change are very likely to exceed rates of evolutionary adaptation in many species (high confidence). Habitat loss and fragmentation are very likely to limit species migration in response to shifting climatic zones (high confidence).
Vulnerability is likely to rise due to an increase in extreme events: Economic damage from extreme weather is very likely to increase and provide major challenges for adaptation (high confidence).
Vulnerability is likely to be high by 2050 in a few identified hotspots: In Australia, these include the Great Barrier Reef, eastern Queensland, the South-West, Murray-Darling Basin, the Alps and Kakadu wetlands; in New Zealand, these include the Bay of Plenty, Northland, eastern regions and the Southern Alps (medium confidence).
Regional climate models (RCMs) are higher resolution physical simulations of climate for a limited area of the globe. Typically the resolution might range from 30 to 50 km, which contrasts to a Global Climate Model (GCM) which might have a resolution of about 300 km. Unlike many GCMs, RCMs do not generally have an ocean component. They simulate the main atmospheric-land processes that influence climate. RCMs are nested within a GCM and variables like atmospheric winds, temperature and humidity from a GCM are used as input to the RCM.
NIWA has been implementing the RCM of the United Kingdom Met Office (known as PRECIS) and using it to simulate New Zealand climate under historic conditions, as well as for a limited number of future scenarios. The model requires atmospheric inputs from a version of the United Kingdom Met Office GCM called HadAM3P, or from reanalyses such as ERA-40. Currently the model has been used to simulate the A2 and B2 emission scenarios for a future time slice of 2070 to 2100. There are also a number of historical and experimental runs.
This figure illustrates how climate models "see" New Zealand with the typical spatial resolution of a Global Climate Model (GCM, top, ~140km resolution) and a Regional Climate Model (RCM, bottom, ~30km resolution).
Prepared by David Wratt and Sam Dean