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STATISTICAL ANALYSIS OF ABRUPT CLIMATE CHANGES

STATISTICAL ANALYSIS OF ABRUPT CLIMATE CHANGES. Melisa Menéndez*; I. J. Losada; F. J. Méndez; J. Grimalt; M. Canals; B. Martrat. * Instituto de Hidráulica Ambiental, IHCantabria, Universidad de Cantabria. future. ?. t. Frequency (a). ?. t. Intensity (b). We are interested on.

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STATISTICAL ANALYSIS OF ABRUPT CLIMATE CHANGES

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  1. STATISTICAL ANALYSIS OF ABRUPT CLIMATE CHANGES Melisa Menéndez*; I. J. Losada; F. J. Méndez; J. Grimalt; M. Canals; B. Martrat. * Instituto de Hidráulica Ambiental, IHCantabria, Universidad de Cantabria

  2. future ? t Frequency (a) ? t Intensity (b) We are interested on.. Studying the Abrupt Climate Changes (ACC) events in the past • Modeling the occurrence of ACC (Frequency) • Modeling the abrupt Temperature changes (Intensity) • Quantifying the influence of possible forcings • Analyze time variations of interest (cycles?)

  3. METHODOLOGY Randomvariable, X Stochasticprocess • The basic idea.. Sample Tª time (bp) Cumulative distribution function ↔ Probability density function cdf pdf

  4. METHODOLOGY • The basic idea.. INTENSITY FREQUENCY Pareto distribution Poisson distribution (Abrupt changes require a minimum magnitude) (Rare events process)

  5. METHODOLOGY • But…..Is it a stationary process? Number of ACC ACC has characteristics that change systematically through the time

  6. METHODOLOGY Non-Stationary process Stationary process The probability that a ACC happens, of a magnitude, varies through time

  7. METHODOLOGY • Identifying ACC events..

  8. METHODOLOGY • Identifying ACC events..

  9. METHODOLOGY • Statistical Model INTENSITY FREQUENCY Pareto distribution Poisson distribution

  10. METHODOLOGY • Statistical Model FREQUENCY Poisson distribution Occurrence rate varies through time INTENSITY Pareto distribution Magnitude of Tª change varies through time

  11. METHODOLOGY • Potential covariates Climatic Theory of Milankovitch Milankovitch cycles are the collective effect of changes in the Earth's movements upon its climate This theory explains climatic changes by orbital parameters: axial tilt

  12. METHODOLOGY • Potential covariates • Isolation • Eccentricity • Obliquity • Precession

  13. METHODOLOGY • Potential covariates

  14. METHODOLOGY • Potential covariates

  15. METHODOLOGY • Potential covariates To obtain the simplest possible model (following the principle of parsimony) that fits the data sufficiently well: STEPWISE PROCEDURE M2 M1 (5 parámetros) M3

  16. METHODOLOGY • Statistical Model: Fitness Maximum likelihood estimation To study statistical significance of covariates: profile likelihood technique

  17. APPLICATION 1 • Data SST time series in Alborán Sea Martrat et al., 2004

  18. APPLICATION 1 • Data ACC warm events

  19. APPLICATION 1 • Data ACC cold events

  20. APPLICATION 1 • Results FREQUENCY MODEL Main covariate: • Isolation

  21. APPLICATION 1 • Results FREQUENCY MODEL

  22. APPLICATION 1 • Results FREQUENCY MODEL Warming events: • Isolation (0ºN) Cooling events: • Slope of Isolation (45ºN) • + Obliquity • + Eccentricity

  23. APPLICATION 1 • Results INTENSITY MODEL Main covariate: • Eccentricity (- gradient) Mean value 90% quantile

  24. APPLICATION 2 • Data • (~atmosferic temperature) time series in Greenland

  25. APPLICATION 2 • A possible periodic component ? Schulz, M. (2002); Rahmstorf, S (2003); Ditlevsen et al., (2005, 2007); Rohling et al., (2003), … Does it exist the 1470 cycle? ACC warm events

  26. APPLICATION 2 • A possible periodic component ? In spite of the differences, a periodic component should be detected both proxies

  27. APPLICATION 2 • A possible periodic component ?

  28. Conclusions • Los modelos estadísticos se han aplicado satisfactoriamente para el estudio de la influencia de forzamientos externos y la detección de periodicidades en los ACC. • Los resultados obtenidos indican la influencia de la Insolación terrestre en los ACC ocurridos en el pasado, así como una relación de su señal con la latitud en función de si el ACC es un calentamiento/enfriamiento. • El estudio realizado permite identificar cuantitativamente la influencia de los parámetros orbitales en los ACC. • Se ha detectado la presencia de una periodicidad en torno a los 1500 ±200 años en los registros obtenidos de testigos de hielo en Groenlandia. • Further works • Other forcings /covariates ??? • Other proxies with high resolution?

  29. STATISTICAL ANALYSIS OF ABRUPT CLIMATE CHANGES Melisa Menéndez*; I. J. Losada; F. J. Méndez; J. Grimalt; M. Canals; B. Martrat. * Instituto de Hidráulica Ambiental, IHCantabria, Universidad de Cantabria

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