Thomas Homer-Dixon

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Uncertainty, Lags, and NonlinearityChallenges
to Governance in a Turbulent World

• Thomas Homer-Dixon
• CIGI Chair of Global Systems
• Balsillie School of International Affairs
• Waterloo,Canada
• May 7 2009

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UNCERTAINTY LAGS NONLINEARITY OPENNESS
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UNCERTAINTY LAGS NONLINEARITY OPENNESS
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UNCERTAINTY LAGS NONLINEARITY OPENNESS
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We need to shift from seeing the world as
composed mainly of MACHINES to seeing it as
composed mainly of COMPLEX SYSTEMS
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• Whereas MACHINES
• can be taken apart, analyzed, and fully
  understood (they are no more than the sum of
  their parts)
• exhibit normal or equilibrium patterns of
  behavior
• show proportionality of cause and effect, and
• can be managed because their behavior
  predictable . . .

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• COMPLEX SYTEMS
• are more than the sum of their parts (they have
  emergent properties)
• can flip from one pattern of behavior to another
  (they have multiple equilibriums)
• show disproportionality of cause and effect
  (their behavior is often nonlinear, because of
  feedbacks and synergies), and
• cannot be easily managed because their behavior
  is often unpredictable.

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Were moving from a world of RISK to a world
of UNCERTAINTY (unknown unknowns)
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So, we must move from management to
Complex Adaptation
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Battisti and Naylor, Historical warnings of
future food insecurity with unprecedented
seasonal heat. Science (9 January 2009) 240-44
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Battisti and Naylor, Historical warnings of
future food insecurity with unprecedented
seasonal heat. Science (9 January 2009) 240-44
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IPCC 2007
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UNCERTAINTY LAGS NONLINEARITY OPENNESS
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• LAGS
• Between emission and climate response
• Between cuts to emissions and reduction of
  warming
• Between policy decision to change energy
  infrastructure and completion of this change

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We show that to hold climate constant at a
given global temperature requires near zero
future carbon emissions. . . . As a consequence,
any future anthropogenic emissions will commit
the climate system to warming that is essentially
irreversible on centennial timescales. Matthews,
H. D., and K. Caldeira (2008), Stabilizing
climate requires near-zero emissions, Geophys.
Res. Lett.
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The climate change that takes place due to
increases in carbon dioxide concentration is
largely irreversible for 1,000 years after
emissions stop. Following cessation of emissions,
removal of atmospheric carbon dioxide decreases
radiative forcing, but is largely compensated by
slower loss of heat to the ocean, so that
atmospheric temperatures do not drop
significantly for at least 1,000 years. Among
illustrative irreversible impacts that should be
expected if atmospheric carbon dioxide
concentrations increase from current levels near
385 parts per million by volume (ppmv) to a peak
of 450600 ppmv over the coming century are
dry-season rainfall reductions in several regions
comparable to those of the dust bowl era and
inexorable sea level rise. Solomon et al,
Irreversible climate change due to carbon
dioxide emissions, PNAS (February 10 2009).
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Hansen, Atmos. Chem. Phys. 7 (2007) 2287-2312.
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UNCERTAINTY LAGS NONLINEARITY OPENNESS
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Ice Accumulation Rate (meters per year)
Years before Present
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More rapid warming at poles One reason
Ice-albedo feedback
Atmospheric warming
radiative positive feedback, fast
Increased ocean absorption of suns energy
Melting of ice
Lower reflectivity of ocean surface
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2008 4.52 mK2
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Atmospheric warming
carbon cycle positive feedback, potentially fast
Death of forests
Release of CO2
Rotting and burning of organic matter
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Atmospheric warming
carbon cycle positive feedback, slow
Increased airborne fraction
Decreased efficiency of carbon sinks
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Declining efficiency of the ocean sink

• Up to 30 percent decrease in the efficiency of
  the Southern Ocean sink over the last 20 years
• Strengthening of the winds around Antarctica
  increases exposure of carbon-rich deep waters
• Strengthening of the winds due to global warming
  and the ozone hole

Le Quéré et al. 2007, Science
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Atmospheric warming
carbon cycle positive feedback, potentially fast
Release of CH4 and CO2
Melting of permafrost
Rotting of organic matter
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