Is there a credible upper bound for global sea level rise and can we live with it?

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Is there a credible upper bound for global sea
level rise and can we live with it?

• Chaos in a changing climate
• Chaos and Complex Systems Seminar
• UW-Madison, January 27, 2009
• Philip Keillor
• philkeillor_at_charter.net

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Differing perceptions of
chaos

• Chaos is the score upon which reality is
  written.
• Henry Miller, American writer
• Reality is the score upon which chaos is
  written.
• Philip Keillor, American coastal engineer

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My intent for this seminar

• 1. talk about chaos in the climate systemand
  abrupt climate change
• 2. focus on some chaotic elements that may affect
  sea level rise
• 3. show you a wish list for recommendations on
  extreme sea level rise

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View of a climate modeler

• Climate can vary chaotically, i.e., in the
  absence of any forcing. Indeed, the climate
  system exemplifies complexity, a combination of
  deterministic behavior and unpredictable
  variations (noise or chaos)
• Hansen et al, 1997

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Hansen, et al 1997
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Hansen et al, 1997
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Comparison of observed and modeled climate
change 1979-1996 (Hansen et al, 1997)

• Observed climate changes contained unambiguous
  signatures of both natural and anthropogenic
  climate forcings.
• Year-to-year climate changes at middle
  latitudesare primarily chaotic functions.

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Abrupt Climate Change (NRC 2002)

• when the climate system is forced to cross
  some threshold, triggering a transition to a new
  stat at a rate determined by the climate system
  itself and faster than the cause.
• one that takes place so rapidly and
  unexpectedly that human or natural systems have
  difficulty adapting to it.

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Abrupt Climate Change (NRC 2002)

• surprising new findings that abrupt climate
  change can occur when gradual causes push the
  earth system across a threshold
• Chaotic processes in the climate system may
  allow the cause of such an abrupt climate change
  to be undetectably small.

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A brand new definition of abrupt climate change
(USCCP 2008)

• A large scale change in the climate system that
  takes place over a few decades or less, persists
  (or is anticipated to persist) for at least a few
  decades and causes substantial disruptions in
  human and natural systems.

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Dangerous climate change gets public attention

• Feb. 2005. U.K. DEFRAs International Symposium
  on Stabilisation of Greenhouse Gas
  Concentrations, Avoiding Dangerous Climate Change
• July 2005. Tony Blairs main agenda item at G8
  Summit.
• May 2006. David Attenborough hosted a two part
  series Climate Chaos on the BBC
• 2006. Al Gores widely-acclaimed documentary and
  book Inconvenient Truth

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Chaos Found in IPCC 2007

• nonlinearities,
• climate feedbacks,
• internal climate variability,
• tipping points,
• thresholds,
• possibilities of abrupt climate changes

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Some places to look for chaos in climate changes

• 1. hydrologic cycle
• 2. flow of the Gulf Stream
• 3. release of trapped methane
• 4. ecosystem changes
• 5. human systems changes

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More places to look for chaos in climate changes

• 6. the global carbon cycle
• 7. clouds
• 8. aerosols
• 9. ocean wind patterns and currents
• 10. rapid polar glacier melting
• 11. changes in albedo

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A bottom line on climate feedbacks

• The large response of the climate system (to
  orbital forcing) implies a strong amplification
  of this forcing.
• IPCC 2007

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My second pointThe problem of extreme global
sea level rise

• 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.
• (IPCC 2007)

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More problems with extreme global sea level rise

• The long term rise in sea level (beyond 2100)
  will be made significantly larger by the
  breakdown of the West Antarctic and/or Greenland
  ice sheets. In Greenland, this is likely to
  happen by 2100 under the A1B scenarioThis
  questions both the long-term viability of many
  coastal settlements and infrastructureand the
  current trend of increasing human use of the
  coastal zoneThis issue presents a challenge for
  long-term coastal spatial planning...IPCC
  2007

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Prospective global sea level rise (meters)an
apples and oranges comparison
Rise Cond. Ice loss? End Date Source
0.3 - 0.6 BAU No 2090-99 IPCC 07
gtgt 0.6 BAU Yes 2090-99 IPCC 07
0.5 - 1.4 dh/dT No 2100 Rahmstorf 07
lt 5 Nonlin.R. No 2100 Hansen et 07
0.7 - 1.3 N.A. ? 2100 Delta C. 08
2 4 N.A. ? 2300 Delta C. 08
0.8 - 2 Glacial Yes 2100 Pfeffer et 08
0.5 1.5 Paleo.c. Yes 2100 Rohling 08
gtgt 0.6 BAU Yes 2100 USCCSP 08
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One outlook for abrupt climate change(IPCC 2007)

• Abrupt climate changesare not considered likely
  to occur in the 21st centuryHowever, the
  occurrence of such changes becomes increasingly
  more likely as the perturbation of the climate
  system progresses.
• (a modeling-limited outlook)

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An outlook for edges of polar ice sheets(USCCSP
2008)

• About recent, rapid changes at the edges of polar
  ice sheets
• It is unclear whether this imbalance is a
  short-term natural adjustment or a response to
  recent climate change, but processes causing
  accelerations are enabled by warming, so these
  adjustments will very likely (90 probability)
  become more frequent in a warmer climate.
• (an observation span-limited outlook)

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My third point. Desired recommendations on
extreme sea level for planning purposes

• In feasibility studies for coastal projects,
  consider the high probability of accelerated sea
  level rise and strategies that would be
  appropriate for the entire range of uncertainty.
• NRC 1987. Responding to Changes in Sea Level,
  Engineering Implications

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My wish list for estimates by others of extreme
sea level rise

• Consider new (or adjusted) story lines of a
  future world with greenhouse gases and changed
  regional and global temperatures
• Obtain best professional judgment of scientists
  on conditions likely to trigger polar ice sheet
  collapse
• Provide critical review of published estimates of
  rates and amounts of sea level rise

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A Faith Statement Amid Chaos and Climate Change

• It is important not to be fatalistic about the
  threats posed by abrupt climate change.
• NRC 2002

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My observation and hope

• The short time spans of observations and the
  shortcomings of models presently contribute to a
  comfortable blanket of uncertainty that shields
  us from a clear view of future climate.
• Perhaps chaos will bring a new, yet liveable,
  stage of stability to global and regional
  climate.
• philkeillor_at_charter.net

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Your Comments on some places to look for chaos in
climate changes?

• 1. hydrologic cycle
• 2. flow of the Gulf Stream
• 3. release of trapped methane
• 4. ecosystem changes
• 5. human systems changes
• philkeillor_at_charter.net

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Your comments on more places to look for chaos in
climate changes?

• 6. the global carbon cycle
• 7. clouds
• 8. aerosols
• 9. ocean wind patterns and currents
• 10. rapid polar glacier melting
• 11. changes in albedo
• philkeillor_at_charter.net