Abrupt Climate Changein the Glacial-Interglacial Record

AOS 528, 11/27/07

Large changes within less than a 30 year period Abrupt on human time scales (climatology), but…

A transition or response that is rapid comparedto the forcing.

Relevant for any time scale Incorporates the idea of thresholds, but…

Definitions of Abrupt

What’s the forcing and what’s a feedback?What’s the forcing and what’s a feedback?

What is the definition of “large changes”?What is the definition of “large changes”?

CO2

CH4

N2O

Definitions of Abrupt

What is rapid?

Sea Level Rise1880 - 2100Sea Level Rise1880 - 2100

Holocene and Projected Sea Level Rise8,000 BP to 2100Holocene and Projected Sea Level Rise8,000 BP to 2100

Futurerate similar to deglacial sea level rise.~1m percentury

Futurerate similar to deglacial sea level rise.~1m percentury

Glacial-Interglacial Abrupt Events

Abrupt events during glacials were larger and more widespread than during the most recent interglacial (Holocene)

Both cooling and warming events are identified (but none are warmer than modern climate)

Wide varieties of proxy data record these abrupt events

Temperature

Dust / Iron

CO2

Antarctica

Proxy Data and Abrupt Climate Events

Temperature

CH4

MOC

Temperature

Meridional Overturning Circulation

Greenland

nss-Ca2+ = non-sea salt Calcium

Proxy Data Findings

1. Abrupt warming and cooling events are recorded in both Greenland and Antarctica

2. Large methane signal (∆CH4=150ppb)

• possibly related to changes in tropical wetlands or Asian monsoon• low CH4 correlated with increased dust in Antarctica

(cold, dry and windy?)

3. Small carbon dioxide signal (∆CO2=20ppm)

4. Pollen records show equatorward shift of boreal tree lines (cold weather forests) during cooling events

5. Effects are global, but out-of-phase in N. and S. Hemispheres (i.e. Northern and Southern Hemisphere signals are not

synchronous)

Methane vs Carbon Dioxide

1. Large methane signal (∆CH4=150ppb)

• possibly related to changes in tropical wetlands or Asian monsoon• low CH4 correlated with increased dust in Antarctica

(cold, dry and windy?)

2. Small carbon dioxide signal (∆CO2=20ppm)

Abrupt Climate Change and Atlantic Ocean Circulation

Abrupt Cooling: Heinrich Events• Decreased NADW• NADW formation south of

modern location

Abrupt Warming:Dansgaard-Oeschger Events

• Increased NADW• NADW formation north of

modern location

Modern Atlantic Ocean Circulation

Heinrich

Dansgaard/Oeschger

Presentation Instructions1. Submit presentations to me via email attachment by at least 11PM the night

before your presentation.

2. Powerpoint presentations a) 10 minutes + 5 minutes for questions

4 to 8 slides, including a title slide and a final slide summarizing conclusions

b) Each person in the group must present some of the materialc) Use plenty of images, and make sure fonts are large enough to read in

the back of the roomd) Speak so people can hear you in the back alsoe) Talk slowly and precisely, and PRACTICE!

3. Remember that there will be two dates for the Final Powerpoint Presentations: December 6th (during class) and December 20th (during the final exam from 10:05-12:05)

4. Everyone is expected to show up for all group presentations! I will have a sign-in sheet available those days.

Powerpoint Presentations: December 6th

Presentations: Thursday, December 6th (during class)Term papers: Thursday, December 13th (midnight)

Group 2: Phillips, SchiferlThe Effectiveness of the Kyoto Protocol

Group 7: Schmidt, Bruskewitz, Serwe:Title?

Group 8: Schuh, Moore, OlsonEffects of Global Warming on Agriculture Production in the Midwest

Group 9: Kirchner, Shewczyk, WelhouseGlobal Climate Change's Effects On Agriculture

Group 10: Franklin, Obbink, OrlandThe Effects of Orbital Forcings During Mid-Pliocene Global Warming

Powerpoint Presentations: December 20th

Presentations: Thursday, December 20th (10:05am)Term papers: Saturday, December 8th (midnight)

Group 1: Lubcaynka, Moua, PropheterUS and China's Affect on Global Warming

Group 3: Caruso, Maloney, SchmelzerTitle?

Group 4: Schreiber, Brown"Peak Oil" Predictions and Their Effect on Future Warming

Group 5: Asuma, Caves, KochA Comparison of Global Climate Effects Due to Varying Rates of Methane Introduction

Group 6: Marsicek, Ronnei, McCarvilleUsing Drought Index to Analyze Potential Impacts on the Tropical Rainforest By Increasing CO2 and Solar Luminosity

Group 11: Hladish, KampaA Potential Glacial Maximum in the Future?