AR4 WG1 | Climate Change 2007: The Physical Science Basis IPCC

1. AR4 WG1 | Climate Change 2007: The Physical Science Basis IPCC S6.4: Glacial-Interglacial Variability and Dynamics [ 6.4.1.4 - 6.4.3.3 ] [ppt made for CHEM410 The Science of Climate Change] Ciaran Shaughnessy BS Chemistry Illinois Institute of Technology

2. S3.8: Changes in Extreme Events Summary Abrupt climate changes have occurred in cycles throughout geological history. Modeling and research reproduces the mechanisms and predicts future changes. Anthropogenic influence is evident in this cycle. IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

3. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.1.4 | How realistic are simulations of terrestrial carbon storage at the LCM? LGM(Last Glacial Maximum): The era when the ice sheets were fully extended during the last glaciation IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

4. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.1.4 | How realistic are simulations of terrestrial carbon storage at the LGM? There was a significant reduction of CO2 at LGM Less CO2 means less trees Models compatible with research IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

5. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.1.5 | How long did the previous interglacials last? 3,000 – 30,000 years 30,000 years because of orbital eccentricity orbital eccentricity: is the amount by which an astronomical body deviates from a perfect circle.1 IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

6. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.1.6 | How much did Earth warm during the previous interglacial? 3-5 degrees, ice core records Inconsistent with models IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

7. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.1.7 | What is known about the mechanisms of transitions into ice ages? Milankovitch Theory Reduced summer insolation at NNH extends glaciers IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

8. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.1.8 | When will the current interglacial end? No trends/Earth processes suggest near cooling Low eccentricity for next 10,000s years GHGs may delay next glacial period IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

9. S6.4: Glacial-Interglacial Variability and Dynamics IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

10. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.2: Abrupt Climate Changes in the G-I Record Abrupt Climate Change: (1) large change in less than 30 years OR (2) rapid response to forcing IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

11. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.2.1 | What is the evidence for past abrupt climate changes? ACCs have occurred repeatedly throughout the past glacial interval Dansgaard-Oeschger events (e.g., Greenland warming) Heinrich events (e.g., NA iceberg discharge) IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

12. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.2.1 | What is the evidence for past abrupt climate changes? IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

13. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.2.2 | What is known about the mechanism of these abrupt changes? Salinity changes and melt water run-off induce ocean circulation Ocean circulation changes linked to surface ACCs When NA cools, SH warms IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

14. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.2.3 | Can climate models simulate these abrupt changes? Model simulations broadly reproduce ACC behavior Underestimated past ACC? IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

15. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.3 | Sea Level Variations Over the Last G-I Cycle IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

16. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.3.1 | What is the influence of past ice volume change on modern sea level change? Sea level changes regardless of anthropogenic influence Degalciation causes gravitational distortion Horizontal redistribution of water IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

17. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.3.2 | What was the magnitude of the G-I sea level change? 120 m IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

18. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.3.3 | What is the significance of the higher-than-present sea levels during the last interglacial period? Ice-sheet melting rises ocean levels 4-6m higher-than-present implies Antarctic contributions IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

19. S6.4: Glacial-Interglacial Variability and Dynamics 6.4.3.4 | What is the long-term contribution of polar ice-sheet derived melt water to the observed globally average rate of sea level rise? 0.2 mm yr-1 , insignificant IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

20. S6.4: Glacial-Interglacial Variability and Dynamics Recap ACCs occur in cycles and we know how Anthropogenic forcings can influence ACC cycle processes IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

21. END IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis

22. References 1. Wikipedia [www.wikipedia.com] IPCC WG1, AR4, Climate Change 2007: The Physical Science Basis