Climate change scenarios: global and local

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 worldwill 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 worldwith uneven development vs.convergent worldwith strongfocus 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 2100. 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. Potentialfor 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 expected annual average damage / costs adapted range average damage threshold Schematic example: changes in drought risk

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

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

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 Central govt guidanceand support Local govt/businesspolicies and plans Adaptation is a process involving various stakeholders Science sector Council/business Community Civil society Central/local govt 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