Oluwakemi Izomo

Hans-Peter PlagOctober 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 variabilityTrend 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 variabilityTrend 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

<------------Holocene------------>

Global Sea Level ChangesGlobal Temperature Changes

<--Holocene-->

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

HolocenHolocenee

HolocenHolocenee

Carbon Dioxide

<--------800,000 years------->

21st Century: Post-21st Century: Post-HoloceneHolocene

21st Century: Post-21st Century: Post-HoloceneHolocene

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 Edge @ RunningInFog)

“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 ...

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 dramaticallyRapid melting of West Antarctic Ice Sheet: up to 4.8 m sea level rise

What Does this Mean for Sea What Does this Mean for Sea Level?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 riseAntarctica: minor contributionMain 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 iceAlready happening: Increases in extinction threats

12 May 2014

May 12, 2014: A large section of the May 12, 2014: A large section of the mighty West Antarctic ice sheet has mighty West Antarctic ice sheet has

begun falling apart ... That’s enough ice begun falling apart ... That’s enough ice to raise global sea level by more than 15 to raise global sea level by more than 15

ft. (4.6 m)ft. (4.6 m)

May 12, 2014: A large section of the May 12, 2014: A large section of the mighty West Antarctic ice sheet has mighty West Antarctic ice sheet has

begun falling apart ... That’s enough ice begun falling apart ... That’s enough ice to raise global sea level by more than 15 to raise global sea level by more than 15

ft. (4.6 m)ft. (4.6 m)

18 May 2014

The glaciers of The glaciers of Greenland are Greenland are likely to retreat likely to retreat

faster and further faster and further inland than inland than anticipatedanticipated

The glaciers of The glaciers of Greenland are Greenland are likely to retreat likely to retreat

faster and further faster and further inland than inland than anticipatedanticipated

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

During that time, During that time, the sea level on a the sea level on a global basis rose global basis rose about 50 feet in about 50 feet in just 350 yearsjust 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 km3 yr−1. Greenland contributes nearly 75% to the total volume change with

−375 ± 24 km3 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 riseAntarctica: minor contributionMain contribution: steric changes

Knowledge in 2014:Greenland: is contributing, is accelerating, potentially a large contribution to sea level riseAntarctica: West Antarctic ice sheet (WAIS) will contribute 4.5 m

WAIS Contribution to Global Sea Level