Oluwakemi Izomo

1. Oluwakemi Izomo

2. Trends or Transitions The Challenge: Leaving the Holocene What does this mean for Sea Level Anticipating Surprises Hans-Peter Plag October 6, 2014

3. Distinction between trends and hazardous events • Trends change the hazard spectrum: • can cause more frequent, more extreme hazards • can lead to new hazards or eliminate old ones

4. Trends in the environment: • climate change and its consequences • global warming • sea level rise and ocean circulation • ocean chemistry • ecosystem impacts • crossing global boundaries (leaving the Holocene) • biodiversity • Nitrogen cycle • water cycle • land use • diseases and resistance

5. Distinction between trends and hazardous events • Trends change the hazard spectrum: • can cause more frequent, more extreme hazards • can lead to new hazards or eliminate old ones Importance of trends depends on background variability Trend or Transition/Jump? Is the system transitioning to a new state?

7. Distinction between trends and hazardous events • Trends change the hazard spectrum: • can cause more frequent, more extreme hazards • can lead to new hazards or eliminate old ones Importance of trends depends on background variability Trend or Transition/Jump? Is the system transitioning to a new state? “Global Warming” is not a trend but rather a transition to a new system state. The Challenge: Leaving the Holocene

8. IPCC, 2013

9. Global Temperature Changes Global Sea Level Changes <--Holocene--> <------------Holocene------------> The Holocene was a “safe operating space for humanity” The Baseline: During the Holocene, global temperature, climate, and sea level were exceptionally stable. The Holocene, the most recent geological epoch, started 11,700 years ago Marcott et al., 2013

10. Carbon Dioxide Global Temperature in the Post-Holocene 21st Century: Post-Holocene Holocene <--------800,000 years-------> We are moving to a planet unknown to humanity ...

11. “Safe operating space for humanity” Rockstroem et al., 2009 Humanity as a global species is on the edge Earth is on the Edge We don’t know where the edges are, but we keep running faster and faster ... (On The Edge @ RunningInFog)

12. “Has human activity over the past two centuries pushed the Earth out of the Holocene and into the Anthropocene?” James Syvitski, 2012. We have moved from the back seats of the bus into the driver seat ... We need leadership that can drive the bus and keep it on a safe track ...

13. And it seems pretty obvious that the time has arrived to prepare for the consequences of unsustainability, ... Robert Engelman, 2013; president, World Watch Institute The planet is on a rocky path unknown to humanity; to more variability ... We need to develop adaptive capabilities to handle surprises ... Rapid ocean acidification can reduce marine food resources dramatically Rapid melting of West Antarctic Ice Sheet: up to 4.8 m sea level rise

14. What Does this Mean for Sea Level? Warmer Climates Mean Higher Sea Level

15. Century Global Sea Level Changes Scientifically, we cannot exclude a large, rapid global sea level rise with large spatial variability in local sea level rise. Century Global Surface Temperature Changes A Colleague (2008, pers. comm.): “There is not enough ice around to cause a rapid sea level rise” Hansen et al. (2008) Plag and Jules-Plag (2013)

16. Anticipated 21st Century Sea Level Rise Note: No accelerated contribution from Greenland and Antarctic ice sheets consider Accepted knowledge in 2000: Greenland: no significant contribution to sea level rise Antarctica: minor contribution Main contribution: steric changes Could there be Surprises? IPCC, 2013

17. Started in 2003: Gravity Recovery and Climate Experiment (GRACE)

18. The last 10 years of observing the ice sheets have revealed many surprises ...

19. National Research Council in 2013: There is the potential for surprises and new extremes ... Already happening: Disappearance of late-summer Arctic sea ice Already happening: Increases in extinction threats Disruption of Atlantic Meridonal Overturing Circulation: unlikely in the 21st century; but gradual chance could have severe consequences Greenland ice sheet: abrupt changes very unlikely in the 21st century West Antarctic Ice Sheet: up to 4.8 m sea level rise; abrupt changes unlikely in the 21st century Most likely (low-probability) rapid impact: ocean acidification

20. 12 May 2014 May 12, 2014: A large section of the mighty West Antarctic ice sheet has begun falling apart ... That’s enough ice to raise global sea level by more than 15 ft. (4.6 m)

21. The glaciers of Greenland are likely to retreat faster and further inland than anticipated 18 May 2014

22. During that time, the sea level on a global basis rose about 50 feet in just 350 years 28 May 2014

23. Rapid melting of West Antarctic Ice Sheet: up to 4.8 m sea level rise September, 2014: The combined volume change of Greenland and Antarctica for the observation period is estimated to be −503 ± 107 km3 yr−1. Greenland contributes nearly 75% to the total volume change with −375 ± 24 km3 yr−1

24. 4.5 m Accepted knowledge in 2000: Greenland: no significant contribution to sea level rise Antarctica: minor contribution Main contribution: steric changes WAIS Contribution to Global Sea Level Knowledge in 2014: Greenland: is contributing, is accelerating, potentially a large contribution to sea level rise Antarctica: West Antarctic ice sheet (WAIS) will contribute 4.5 m 800 Years? 100 Years? How worried should we be?