1. Climate change scenarios: global and local
NZCCC Adaptation Conference ‘09
Andy Reisinger 1
with Martin Manning 1, Brett Mullan 2, David Wratt 2, Richard Nottage 2
1 Climate Change Research Institute, School of Government, Victoria University
2 National Institute of Water and Atmospheric Research (NIWA)

2. Scenarios: alternative futures
Future climate change depends on future greenhouse gas emissions
Future greenhouse gas emissions depend on socio-economic choices
We cannot predict the socio-economic choices the world will make.
But we can ask “what if” any particular choice became reality?
Figures based on Meinshausen et al., Nature 2009

3. Scenarios: alternative futures
Future climate change depends on future greenhouse gas emissions
Future greenhouse gas emissions depend on socio-economic choices
Different impacts globally
Different socio-economic drivers: fractured world with uneven development vs. convergent world with strong focus on multilateralism
high carbon world
rapidly
decarbonising world
Figures based on Meinshausen et al., Nature 2009

4. Climate change scenarios: implications
Implications of alternative scenarios:
(obviously) different climate and impacts for NZ
but also: different impacts around the world
and also: very different settings for international policy, technology, sustainability, cooperation
NZ intimately connected with rest of the world through tourism, exports, security, aid, migration, technology and raw materials → flow-on effects !

5. Climate change scenarios for NZ
Methodology
select IPCC models that do the best job in reproducing current/recent climate in Pacific
select model information for two scenarios
high carbon world (SRES A2)
rapidly decarbonising world (scale SRES B1 scenario so that global warming is limited to 2°C by end 21st century)
estimate global warming for two missing model runs
down-scale models to high resolution over NZ
change in seasonal average climate parameters
changes in extremes more difficult to model

6. NZ scenarios: temperature
Scenario information provided by B. Mullan, NIWA

7. NZ scenarios: temperature
Scenario information provided by B. Mullan, NIWA

8. NZ scenarios: temperature
Inter-model variations in temperature
Scenario information provided by B. Mullan, NIWA

9. NZ scenarios: winter precipitation
Scenario information provided by B. Mullan, NIWA

10. NZ scenarios: winter precipitation
Scenario information provided by B. Mullan, NIWA

11. NZ scenarios: summer precipitation
Scenario information provided by B. Mullan, NIWA

12. NZ scenarios: summer precipitation
Scenario information provided by B. Mullan, NIWA

13. NZ scenarios: precipitation
Inter-model variations in precip: south-west South Island
Scenario information provided by B. Mullan, NIWA

14. NZ scenarios: precipitation
Inter-model variations in precip: east North Island
Scenario information provided by B. Mullan, NIWA

15. Climate change scenarios: sea level
Very rapidly moving area of science:
IPCC model-based projections: 18-59cm by 2100 …
… but no best estimate or upper limit. Acceleration of polar ice loss could lead to greater sea level rise.
Recent studies suggest sea level rise could significantly exceed 1m by Sea level very likely to continue to increase for many more centuries beyond 2100.
No convergence yet between recent studies. Uncertainty unlikely to be resolved in the next few years. Potential for rapid rise is a key reason for concern.
Picture: National Oceanic and Atmospheric Administration (NOAA), US

16. Climate change scenarios: extremes
Extremes key part of climate change:
Even a small change in mean climate can result in significant changes in climatic extremes.

17. Climate change scenarios: extremes
Schematic example: changes in drought risk
expected annual
average damage / costs
adapted range
average
damage threshold

18. Climate change scenarios: extremes
Schematic example: changes in drought risk
change in mean climate
expected annual
average damage / costs
adapted range
average
average
damage threshold

19. Climate change scenarios: extremes
Schematic example: changes in drought risk
change in mean climate
and in variability
expected annual
average damage / costs
adapted range
average
damage threshold

20. Climate change scenarios: extremes
Extremes key part of climate change:
Changes in means imply altered frequency of extremes.
Key climatic extremes:
extreme temperatures (hot days ↑, heat wave ↑, frost ↓)
heavy precipitation and flood risk ↑
drought risk in eastern/northern regions ↑
less certain: storm surge, storms, extratropical cyclones
Quantitative projections currently difficult:
default: historical variability superimposed on trend
Regional Climate Model (RCM) key advance

21. Adapting to climate change
less of a problem for NZ?
less warming than rest of world …
… don’t be too sure about that:
sea level rise same as global average (if not more)
much smaller budget than larger countries …
… but same complexity and range of issues
decentralised approach to decision-making
high dependence on natural resources and exports
flow-on effect of global changes

22. Adaptation process
Adaptation is a process involving various stakeholders
Science sector
Council/business
Community
Civil society
Central/local govt
Central govt guidance and support
Local govt/business policies and plans
Figure by R. Warrick, IGCI (Warrick, 2000)

23. Adaptation challenges
When to adapt:
reactive: wait for need/opportunity from climate change
context-specific: when other pressures create opportunity
proactive/planned: to avoid unsustainable lock-in
Decisions require social value-judgements:
discounting over time: are we prepared to incur short-term opportunity costs to avoid longer term risks?
attitude to risk: how to handle low-probability/high-impact event; who pays if the unlikely event happens?
sustainability trade-offs: how do we balance economic, social and environmental risks and gains?

24. Adaptation needs in various sectors
Figure from IPCC WGII, Chapter 11: Hennessy et al, 2007

25. Climate change scenarios: summary
2 scenarios to highlight contrasting futures
pattern of climate change in NZ broadly similar but much more pronounced under high carbon world
climatic extremes change more rapidly/significantly than averages, and are often more relevant
adaptation is a complex process involving multiple stakeholders and steps towards implementation
value judgements are integral part of adaptation
impacts and adaptation options in NZ depend on
climate and socio-economic changes
domestically and internationally

26. Adaptation needs in various sectors
Figure from IPCC WGII, Chapter 11: Hennessy et al, 2007