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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.

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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


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


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


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


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


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


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


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


S6.4: Glacial-Interglacial Variability and Dynamics

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


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


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


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


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


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


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


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


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


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


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


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


END

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


References

1. Wikipedia [www.wikipedia.com]

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


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