Act Talk - Vasilis Dakos: Expecting the unexpected
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Transcript of Act Talk - Vasilis Dakos: Expecting the unexpected
Vasilis Dakos
Aquatic Ecology and Water Quality Management Group Wageningen University, The Netherlands [email protected], (www.aew.wur.nl/UK/)
Expecting the unexpected:Leading indicators of regime shifts
Nordwijk March 2010
[transitions]
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Clear lakes get turbid
Scheffer and Carpenter, 2003
algae dominated state
macrophyte dominated state
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Cod in North Atlantic crashes
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
deMenocal et al, 2000
The Sahel turned into desert
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Earth climate systems shift
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Financial markets collapse
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Ave
rage
jour
ney
time
We get stuck in traffic jams
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Humans get epileptic seizures
Can we foresee if a system approaches a transition?
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Can we foresee if a system approaches a transition?
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Even if we do not understand the system?
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Same shift different causes:
Small changes big surprisesBig changes big surprises
Critical transition
It depends…
Scheffer 2009
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Critical Transitions workshop 2007
Early Warning Signals
for critical transitions
as Indicators of Resilience
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts Scheffer and Carpenter, 2003
Why should we expect early-warning signals?
Bifurcation point
Eigenvalue goes to zero
Critical slowing down prior to a transition
Van Nes & Scheffer, 2007
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
What does the “eigenvalue goes-to-zero” mean?
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Consequences of critical slowing down
Indicators of transitions in time
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Indicators of transitions in time
Rising variance
Carpenter & Brock, 2006
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Indicators of transitions in time
Guttal & Jayaprakash, 2008
Increasing skewness
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Held & Kleinen, 2004
Indicators of transitions in time
Increasing autocorrelation at-lag-1
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Indicators of transitions in space
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Indicators of transitions in space
pattern formation
Rietkerk et al, 2004
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Indicators of transitions in space
Kéfi et al, 2007
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Increasing grazing
Truncated power law
Spatial Variance
Spatial Skewness
Indicators of transitions in space
Guttal & Jayaprakash, 2008
Spatial Mean
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
overexploited
underexploited
Dakos et al, early online
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Indicators of transitions in space
Increasing spatial correlation
Turbid state
Clear state
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
The indicators seem to work well on models…
23 juni 2005
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Do the indicators work in reality?
But…
23 juni 2005
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Slowing down precedes ancient climate shifts
Shutdown of thermohaline circulation
Model prediction Data
end of Younger Dryas
Dakos et al, 2008
23 juni 2005
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Slowing down precedes ancient climate shifts
Dakos et al, 2008
…more examples
23 juni 2005
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Increasing variance precedes epileptic attacks
McSharry et al, 2003; Scheffer et al, 2009
23 juni 2005
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Increased spatial variance prior to community reorganization
Litzow et al, 2008
� Indirectestimates of resilience(indication of proximity to transition not predictive tools)
�Tools for verifying past regime shifts (indication in establishing a sudden change as a critical transition)
�Limitationsin their estimation in real systems (data length, data resolution, scale issues)
�Practical applicability:may work better in spatial than temporal context
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Few concluding points
�How can we identify false positives? (need for proceedures to increase statistical power)
�What kind of monitoring schemesthat can capture the indicators do we need to design?
�Can we develop empirical tests for the indicators next to monitoring for probing the resilience of the system?
�Are they only relativemeasures? Or could an one-timesampling estimate indicate how much fragile the system is?
�How much early is early enough?
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Challenges
23 juni 2005
Thank you for your attention!
Vasilis Dakos Wageningen University Expecting the unexpected: Leading indicators of regime shifts
Scientists Seek Warning Signs for Catastrophic Tipping Points
Nordwijk March 2010