Atmospheric Research Can you gradually fall off a cliff? – A glimpse at complex, self-organising systems Roger N. Jones AIACC Training Workshop on Adaptation and Vulnerability TWAS, Trieste June

Atmospheric Research The awakening of complexity Mechanical world of the 19th century Few mysteries left for science to solve The universal machine Mastery over nature The march of progress Modernism The 20th century – transition Quantum physics Chaos and “strange attractors” isolated “frame of reference” exposed as a scientific construct search for a process to counterbalance reductionism Postmodernism

Atmospheric Research Contributions to complex systems science Adam Smith “The invisible hand” Einstein, Bohr, Pauling et al. – quantum physics Schroedinger et al. – uncertainty Turing and Von Neumann – self-replicating automata and game theory Kuhn – the scientific process is linked to social processes Prigogine – complex chemistry Lorenz, Gleick et al. – chaos Holland, Conway et al. – artificial life Bak et al. – self organising systems Arthur – law of increasing returns (economics) Capra – role of eastern philosophy and many others

Atmospheric Research Simple system Mechanistic Replicable Largely linear Can be isolated from other systems Predictable

Atmospheric Research Complex system Organic/chaotic (often described as on the edge of chaos because both organised and chaotic behaviour are recognised) Non-replicable Cannot be isolated from other systems Non-linearity and thresholds both common Self-organising (self-adapting) Bifurcations occur over time Uncertainty is intrinsic

Atmospheric Research Examples Qwertyuiop VHS/Beta DOS/CPM Extinctions/radiation (evolution)

Atmospheric Research Fractal patterns are “natural”

Atmospheric Research Glacial cycles are driven by changes in the Earth’s orbit

Atmospheric Research Holocene rainfall and evaporation – W. Victoria

Atmospheric Research

Weather events

Atmospheric Research CO 2 emissions and concentrations

Atmospheric Research Global warming

Atmospheric Research Likelihood Probability can be expressed in two ways: 1. Return period / frequency-based (Climate variability) 2. Single event (Mean climate change, one-off events)

Atmospheric Research Return period / frequency-based probability Recurrent or simple event Where a continuous variable reaches a critical level, or threshold. Eg. Extreme temperature (max & min), Extreme rainfall, heat stress, 1 in 100 year flood Discrete or complex event An event caused by a combination of variables (an extreme weather event) Eg. tropical cyclone/hurricane/typhoon, ENSO event

Atmospheric Research Frequency-based probability distributions

Atmospheric Research Coping range under current climate

Atmospheric Research Thresholds A non-linear change in a measure or system, signalling a physical or behavioural change Climate-related thresholds are used to mark a level of hazard

Atmospheric Research Single-event probability Singular or unique event An event likely to occur once only. Probability refers to the chance of an event occurring, or to a particular state of that event when it occurs. Eg. Climate change, collapse of the West Antarctic Ice Sheet, hell freezing over

Atmospheric Research What is the probability of climate change? 1. Will climate change happen? IPCC (2001) suggests that climate change is occurring with a confidence of 66% to 90% 2. What form will it take? Uncertainties are due to: future rates of greenhouse gas emissions sensitivity of global climate to greenhouse gases regional variations in climate decadal-scale variability changes to short-term variability

Atmospheric Research Range of uncertainty

25 cm 50 cm 75 cm

Atmospheric Research Non-linear climate change Non-linear climate events - ice ages, Younger Dryas, collapse of the WAIS Climate surprises - climate events that occur unexpectedly Climate surprises are likely to occur on a regional basis under climate change but when and where remains unknown.

Atmospheric Research System responses Resistance (e.g. seawall) Resilience (e.g. regrowth, rebuilding after storm or fire) Adaptation (adjustments made in response to stress) Transformation (old system stops, new one starts) Cessation (activity stops altogether)

Atmospheric Research Can you gradually fall off a cliff? Yes, if you use a model But not in the real world