Oluwakemi Izomo

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

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

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

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?

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

IPCC, 2013

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

HoloceneHolocene Carbon Dioxide 21st Century: Post- Holocene Global Temperature in the Post- Holocene We are moving to a planet unknown to humanity...

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

“Has human activity over the past two centuries pushed the Earth out of the Holocene and into the Anthropocene?” James Syvitski, 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...

The planet is on a rocky path unknown to humanity; to more variability... And it seems pretty obvious that the time has arrived to prepare for the consequences of unsustainability,... Robert Engelman, 2013; president, World Watch Institute 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

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

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

IPCC, 2013 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 Anticipated 21st Century Sea Level Rise Could there be Surprises?

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

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

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

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)

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

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

Rapid melting of West Antarctic Ice Sheet: up to 4.8 m sea level rise September, 2014: September, 2014: The combined volume change of Greenland and Antarctica for the observation period is estimated to be −503 ± 107 km 3 yr −1. Greenland contributes nearly 75% to the total volume change with −375 ± 24 km 3 yr −1

800 Years? 4.5 m 100 Years? How worried should we be? Accepted knowledge in 2000: Greenland: no significant contribution to sea level rise Antarctica: minor contribution Main contribution: steric changes 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 WAIS Contribution to Global Sea Level