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Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
Tim Lenton - Early warning of climate tipping points
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Tim Lenton - Early warning of climate tipping points

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Presentation at the STEPS Conference 2010 - Pathways to Sustainability: Agendas for a new politics of environment, development and social justice …

Presentation at the STEPS Conference 2010 - Pathways to Sustainability: Agendas for a new politics of environment, development and social justice

http://www.steps-centre.org/events/stepsconference2010.html

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  • 1. Early warning of climate tipping points Tim Lenton School of Environmental Sciences, University of East Anglia, Norwich With special thanks to Valerie Livina, John Schellnhuber, Frank Kwasniok
  • 2. Outline Tipping elements Risk assessment Early warning
  • 3. Two types of tipping point Bifurcation
  • 4. Two types of tipping point Bifurcation No bifurcation
  • 5. Policy relevant forcing range IPCC (2007) = High growth = Mid growth = Low growth
  • 6. Tipping elements in the climate system Revised from original in Lenton et al. (2008) PNAS 105(6): 1786-1793 October 11, 2010
  • 7. Estimates of proximity Lenton & Schellnhuber (2007) Nature Reports Climate Change Results from literature review and workshop
  • 8. Likelihood of tipping Kriegler et al. (2009) PNAS 10.1073/pnas.0809117106 Imprecise probability statements from experts Atlantic formally combined Under 2-4 °C warming: Greenland >16% probability of passing at least one of five tipping points Antarctica Under >4 °C warming: >56% probability of passing at least one of Amazon five tipping points El Niño
  • 9. Impacts of tipping Lenton, Footitt & Dlugolecki (2009) http://assets.panda.org/downloads/plugin_tp_final_report.pdf Populations exposed to 1-in-100-yr flood events Allianz / WWF report: Increased sea level rise +$25,158 billion exposed assets in port megacities Indian summer monsoon disruption Amazon dieback and drought Aridification of southwest North America October 11, 2010
  • 10. Tipping element risk assessment Tipping element Likelihood of Relative Risk score Risk ranking passing a tipping impact** of (likelihood x point change in state impact) (by 2100) (by 3000) Arctic summer sea-ice High Low 3 4 Greenland ice sheet Medium-High* High 7.5 1 (highest) West Antarctic ice sheet Medium* High 6 2 Atlantic THC Low* Medium-High 2.5 6 ENSO Low* Medium-High 2.5 6 West African monsoon Low High 3 4 Amazon rainforest Medium* Medium 4 3 Boreal forest Low Low-Medium 1.5 8 (lowest) *Likelihoods informed by expert elicitation **Initial judgment of relative impacts is my subjective assessment Impacts depend on human responses hence are more epistemologically contested than assigning likelihoods to events (Stirling 2003 ‘Risk, uncertainty and precaution…’) October 11, 2010
  • 11. Prospects for bifurcation early warning Held & Kleinen (2004) Geophysical Research Letters 31: L23207 Lenton et al. (2008) PNAS 105(6): 1786-1793 Generic early warning signals: Slowing down Increasing variability Skewness of responses Flickering between states System being forced past a tipping point October 11, 2010
  • 12. Model test of early warning method Held & Kleinen (2004) Geophysical Research Letters 31: L23207 CLIMBER-2 intermediate complexity model Linear increase in CO2 from 280 to 800 ppmv Stochastic perturbation of freshwater forcing
  • 13. Fully 3-D dynamical model test Lenton et al. (2009) Phil. Trans. A 367: 871-884 Atlantic meridional overturning circulation Early warning indicator from autocorrelation function Early warning indicator from detrended fluctuation analysis October 11, 2010 GENIE-2 model
  • 14. Paleo-data test of early warning method Livina & Lenton (2007) Geophysical Research Letters 34: L03712 Greenland ice-core regional temperature record Early warning indicator from detrended fluctuation analysis Early warning indicator from autocorrelation function October 11, 2010
  • 15. Detecting the number of system states Livina, Kwasniok & Lenton (2010) Climate of the Past, 6: 77-82 New method; „potential analysis‟: Assume polynomial potential and random noise Estimate number of states (i.e. order of polynomial) Estimate noise level Derive potential coefficients and hence shape of potential Number of states: 1, 2, 3, 4 October 11, 2010
  • 16. Changing number of climate states Livina, Kwasniok & Lenton (2010) Climate of the Past, 6: 77-82 Number of states: 1, 2, 3, 4
  • 17. European monthly temperature anomaly (1659-2004) Livina et al. (in revision) Climate Dynamics Number of states: 1, 2, 3, 4 October 11, 2010
  • 18. Atlantic Multi-decadal Oscillation (1856-present) Livina et al. (in revision) Climate Dynamics Number of states: 1, 2, 3, 4
  • 19. Conclusion Tipping elements in the climate system could be triggered this century by anthropogenic forcing The Greenland and West Antarctic ice sheets probably represent the largest risks Some tipping points can be anticipated in principle, but sufficiently high-resolution, long records are often lacking A change in the number of climate states can be detected, in a noisy climate system that is moving between states Improved understanding is needed to help policy makers “avoid the unmanageable and manage the unavoidable” October 11, 2010
  • 20. Find out more http://knowledge.allianz.com/climate_tipping_points/climate_en.html October 11, 2010
  • 21. Example of transition (but not bifurcation) Livina, Ditlevsen, Lenton (submitted) Nonlinear Processes in Geophysics Sigmoid function with red noise, fluctuation exponent 0.7 ACF-propagator (without detrending) is more sensitive to transitions

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