1. Tim Helweg-Larsen & Richard Hawkins

3. The Arctic

4. 1989

5. 2007

6. 1989 2007

7. Arctic Sea Ice Extent Area of ocean with at least 15% sea ice

8. 1989

9. 2007

10. 1989 / 2007 + 5 years− 5 years Ocean Age of Arctic Sea Ice

11. IPCC, WG I (2007) … late summer sea-ice is projected to disappear almost completely towards the end of the 21st century

13. “The Arctic Ocean could be nearly ice-free at the end of summer by 2012” Dr Jay Zwally, NASA “Our projection of 2013 is already too conservative.” Dr Wieslaw Maslowski, US Navy “Worst-case scenarios about sea-ice loss are coming true: the Arctic Ocean could be ice-free in summertime as soon as 2010” Louis Fortier, Université Laval

15. Mark Serreze, NSIDC No matter where we stand at the end of the melt season, it’s just reinforcing this notion that the Arctic ice is in its death spiral.

16. So what?

17. energy

18. So what?

19. Over and above existing model projections

21. 1989 2012?

22. Albedo % of radiation reflected Hugo Ahlenius, UNEP/GRID-Arendal ≈ 0.3°C

26. Permafrost extent in the Northern Hemisphere, http://maps.grida.no/go/graphic/permafrost-extent-in-the-northern-hemisphere

28. 1672 billion tonnes

30. 0.1% melt = 1600 mtc 80% global cut =1600 mtc

31. Existing coupled climate models lack a robust treatment of soil carbon dynamics.

34. The [IPCC] range does not include … contributions from rapid dynamic processes in the Greenland and West Antarctic ice sheets which… could eventually raise sea level by many meters. Lacking such processes… projections based on such models may seriously understate potential future increases. Oppenheimer et al.

35. IPCC, Synthesis (2007) “Because understanding of some important effects driving sea-level rise is too limited, this report does not assess the likelihood, nor provide a best estimate or an upper bound for sea-level rise… therefore the upper values of the ranges are not to be considered upper bounds for sea-level rise.”

38. Over and above existing model projections Additional

39. What does this mean?

40. 2°

41. next ? What

42. end the

43. Tim Helweg-Larsen & Richard Hawkins