Global change: complexity, ecosystems, and socioeconomic systems

Global Change Climate change Land use change Economic change Focus on global… increasing –connectedness –affluence –economic disparity (“equity”)

Complexity: not just climate Complexity is a defining characteristic of natural systems: –Feedbacks –Nonlinearities and thresholds –Lags –Multi-state: asynchrony vs. synchrony –Multi-scale and scaling –Non-equilibrium: time and space –Emergent behavior

Thresholds are Important Excursion Critical Threshold Time Temperature Increase Climate Variability Climate (e.g. Precipitation *Temperature) After Gray, unpublished Thresholds are important: They are the source of unexpected outcomes ??!?!??!?!

Complexity in ecosystems and socioeconomic systems Prediction stymied by system characteristics –Examples: stock market, agricultural yields, ecosystem responses to perturbation Conceptual / theoretical models: –Cellular automata (spatial/neighbor dependence) –Artificial life (emergence, decision, neural networks) –Multi-state models (ball and cup) –Panarchy (scaling)

Adaptation, vulnerability, mitigation, and risk

Definitions of Vulnerability (From 7 Feb) Risk assessment: Risk = Frequency * Vulnerability ISDR*: The conditions determined by physical, social, economic and environmental factors or processes, which increase the susceptibility of a community to the impact of hazards. IPCC: the extent to which climate may damage or harm a system –depends on system's sensitivity but also on its adaptability *International Strategy for Disaster Reduction

Adaptation Adaptation: change in conditions precipitates change in behavior, organization, structure or other fundamental characteristic of entity –Evolutionary adaptation –Social system adaptation –Ecosystem reorganization General theory from evolutionary theory: –gradualism –punctuated equilibrium –catastrophe theory (sandpile analogy)

Mitigation Mitigation: action to reduce severity or seriousness of an impact –Savings and loan or airline bailouts –Pre-adaptation (mitigation through adaptation): resilience –Climate change: GHG mitigation Carbon sequestration, carbon markets Energy conservation Has some element of ability to anticipate, forecast, or better, predict.

If DAI temperature threshold is +1.5C, no carbon tax reduces P(DAI) If DAI temperature threshold is +2.9C, $150/Ton reduces P(DAI) to near 0 (Source: Mastrandrea and Schneider, 2004

5-Point Quantitative Scale for Confidence Levels 95% or greater Very High Confidence 67-95% High Confidence 33-67% Medium Confidence 5-33%Low Confidence 5% or less Very Low Confidence The 5-point confidence scale below is used to assign confidence levels to selected conclusions. The confidence levels are stated as Bayesian probabilities, meaning that they represent the degree of belief among the authors of the report in the validity of a conclusion, based on their collective expert judgment of all observational evidence, modeling results, and theory currently available to them.

Bayes’ Theorem The probability of the prior distribution given the data is equal to: the probability of the data given the distribution multiplied by the probability of the distribution, divided by the probability of the data. Probability of prior given B = likelihood * prior / constant

Bayes’ Theorem: in practice We say a drug test is 99% accurate Means that 99% positive detections among tested people who used the drug AND 99% negative detections among tested people who didn’t use the drug If 0.5% people use, what’s P(use|detection)? Ans: ~33%. Just ask Tyler Hamilton and Floyd Landis. m

Vulnerability and Resilience If vulnerability f(x) of sensitivity, adaptive capacity, and exposure… Resilience is “the flip side”