Impacts of Global Sea-Level Rise: The AVOID Analysis

1. Impacts of Global Sea-Level Rise:The AVOID Analysis Robert Nicholls and Sally Brown School of Civil Engineering and the Environment and the Tyndall Centre for Climate Change Research University of Southampton Southampton SO17 1BJ UK r.j.nicholls@soton.ac.uk Earth Systems Science 2010

2. Plan • Introduction • Methods • Results • Conclusions

3. Global sea-level rise(IPCC, 2007, AR4 WG1)

4. DIVA(Dynamic Interactive Vulnerability Assessment)

5. Input Parameters • A1B socio-economic scenarios • Unmitigated vs. mitigated sea-level rise scenarios • No protection versus quazi-optimum protection scenarios

6. Sea-level rise scenarios

7. A1B.2016 SLR scenario family

8. A1B.2030 SLR scenario family

9. Output Parameters • Wetland Area (Natural Systems) • Floods (Human Systems) • Dike Costs (Adaptation)

10. Saltmarsh losses2080s

11. Mangrove loss2080s

12. Coastal Flooding • Exposure • flood plain population (1 in 1000 year flood plain) • Risk • expected annual frequency (or damage) Exposure x Probability (considers adaptation strategies)

13. 300 250 200 10th percentile Millions of people 150 50th percentile 90th percentile 100 50 0 2030.R 2016.R 2016.R 2030.R 2016.R 2030.R No mitigation No No mitigation mitigation 2020s 2050s 2080s Coastal flood plain population

14. People flooded and no adaptationchange in expected annual frequency

15. People flooded and adaptationchange in expected annual frequency

16. 10000 10th percentile 5000 50th percentile 90th percentile Cost (US dollars/year) (billions) 0 A1B A1B 2016.R 2030.R 2016.R 2030.R 2050s 2080s Protection costsin 2050s to 2080s (1995 dollars)

17. Results -- Summary • Emission reductions will slightly reduce the global losses of saltmarsh and mangrove after the 2050s -- 4 to 7% of the global stock ‘saved’ by the 2080s; • The size of the coastal flood plain population is insensitive to emission reductions; • Emission reductions will reduce the global number of people experiencing flooding by 2050, and the benefits are substantial by 2100, assuming no adaptation; • However, flood impacts still increase by 10 to 20 times under mitigated scenarios and the reductions in flood impacts represent delayed (to the 22nd Century) rather than avoided damages; • Assuming quazi-optimum adaptation greatly reduces the benefits of emissions reduction identified above.

18. Conclusions • For coasts, emission reductions mainly delay rather than avoid 21st Century impacts; • This reflects the ‘commitment to sea-level rise’; • Need more information about mitigation and large sea-level rise and storms; • Collectively, this supports the IPCC AR4 conclusion: “the most appropriate response to sea-level rise for coastal areas is a combination of adaptation to deal with the inevitable rise, and mitigation to limit the long-term rise to a manageable level.”

19. Impacts of Global Sea-Level Rise:The AVOID Analysis Robert Nicholls and Sally Brown School of Civil Engineering and the Environment and the Tyndall Centre for Climate Change Research University of Southampton Southampton SO17 1BJ UK r.j.nicholls@soton.ac.uk Earth Systems Science 2010