New Results since IPCC AR4

1. Scientific Assessments on Climate Change, Oceans, and Small Island Developing States since the IPCC 4th Assessment Report No island left behind

2. New Results since IPCC AR4 • Sea level rise faster than expected • Sea level rise projections higher than in AR4 • Tropical Cyclone risks confirmed • Ocean acidification threatens coral reefs • Copenhagen Accord emission pledges • Conclusions

3. Sea level rise faster than expected

4. Or is it much better than expected?

5. Accelerating loss of ice from Greenland Greenland Mass Loss: Doubled in April 2002–February 2009 time period Velicogna, I. (2009),Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE, Geophys. Res. Lett., 36, L19503, doi:10.1029/2009GL040222.

6. …and Antarctica Antarctic mass loss: more than doubled from 2002-2006 to 2006-2009 Velicogna, I. (2009),Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE, Geophys. Res. Lett., 36, L19503, doi:10.1029/2009GL040222.

7. Risk of rapid sea rise level from ice sheet disintegration • Science cannot exclude 2 m of sea level rise from ice sheet losses over next century • Observed rapid and accelerating loss of ice points to increasing risk 1978 2009 No island left behind

8. Recent sea level rise estimates Source: Rahmstorf, PIK

9. Recent Sea Level Rise Projections Vermeer, M. and S. Rahmstorf (2009). "Global sea level linked to global temperature." Proceedings of the National Academy of Sciences106(51): 21527-21532.

10. Source: Rahmstorf, PIK

11. Tropical cyclone damages • Increases in extreme tropical cyclone intensity will magnify destructive potential of storms • Catastrophic damages on many small islands and low lying coastal regions likely. • Increasing tropical sea surface temperatures have increased the intensity of tropical cyclones in all ocean basins in recent decades.

12. Tropical cyclone - recent projections • Predicted nearly doubling of frequency of category 4 and 5 Atlantic storms by the end of the 21st century (Bender, et al 2010) • Theory and high-resolution models consistently indicate that greenhouse warming will cause the globally averaged intensity of tropical cyclones to increase (Knutson et al 2010)

13. Increasing risks to coral reefs • Widespread mortality of coral reefs in 21st century affecting livelihoods of many millions • 0.6-0.8°C has already triggered massive coral bleaching • 1- 3°C will lead to widespread mortality of coral reefs • Risk grows rapidly with increasing temperature • Ultimately likely complete loss of reefs

15. Source: Rahmstorf, PIK

16. Coral Reefs: CO2 and Ocean acidification • Increasing CO2 concentration acidifying the world oceans • Likely to have wide ranging adverse effects. • 550 ppm CO2 coral reefs dissolve - reached by 2050s • 450 ppm CO2 coral stop growing - reached by 2030s • Below 350 ppm CO2 appears to be ‘safe’ for reefs • CO2 at present 386 ppm and rising at 2ppm/year

17. Future CO2 concentrations and coral reefs Long term limit for reefs

18. Copenhagen Accord: Over 3oC warming

19. The effect of Copenhagen Rogelj et al. 2010

20. Conclusions • Nations will probably meet only lower ends of emissions pledges in absence of binding international agreement • Current pledges • Global emissions 2020 up to 20% higher than today • Greater than 50% chance warming will exceed 3 °C by 2100, CO2 greater than 650 ppm • Sea level rise of ca 1 metre by 2100 above 1990 • Halving emissions by 2050 has 50% chance warming will exceed 2 °C • Almost certainly greater than 1.5 °C

21. Acknowledgements • Stefan Rahmstorf, Malte Meinshausen, Katja Frieler, Claudine Chen, Earth System Research Domain, PIK, Potsdam • Michiel Schaeffer, Climate Analytics GmbH, New York/Potsdam • Joeri Rogelj, ETH, Zurich