Rapid Climate Change

Rapid Climate Change

Lauren ElmegreenESP Seminar

April 28, 2006

Lauren ElmegreenESP Seminar

April 28, 2006

Past Climate: Lake Agassiz

Teller, JT and DW Leverington, 2004

Teller, JT and DW Leverington, 2004

IncreasedSeasonality

Winters becomeeven colder

Less heat is transportedto high latitudes

Sea ice is formed inNorthern Atlantic

Thermohaline circulationslows or shuts down

Sea Ice and Abrupt Climate Change

Denton GH et al, 2005

Possible scenario in current conditions…

IncreasedSeasonality

Thermohaline circulationslows or shuts down

Temperature increases

Sea ice is formed inNorthern Atlantic

Winters becomeeven colder

Less heat is transportedto high latitudes

Schmittner, A., M.Latif and B. Schneider, 2005

Future Climate: Models

Latif, M. et al, 2000

Latif, M. et al, 2000

Rapid climate change in the media

• “Britain faces big freeze as Gulf Stream loses strength” The Times (Britain), Dec 2005

• “Failing ocean current raises fears of mini ice age” New Scientist, Nov 2005

• “Shifting currents renew fears of freezing” The Montreal Gazette, Dec 2005

Summary

• Possible reasons for past rapid climate change– Sea ice formation in North Atlantic– Lake Agassiz

• Model predictions for the future– Models predict gradual changes in THC without a

rapid shutdown– Increased salinity may compensate for density

decreases in Atlantic Ocean

References

• CCNet http://www.staff.livjm.ac.uk/spsbpeis/CCNet-homepage.htm• Denton, G.H., et al, 2005. The role of seasonality in abrupt climate

change. Quaternary Science Reviews, 24, 1159-1182.• Gregory, J.M., et al, 2005. A model intercomparison of changes in the

Atlantic thermohaline circulation in response to increasing atmospheric CO2 concentration. Geophysical Research Letters, 32, L12703.

• Latif, M. et al, 2000. Tropical stabilization of the thermohaline circulation in a greenhouse warming simulation. Journal of Climate, 13, 1809-1813.

• Schmittner, A., M. Latif and B. Schneider, 2005. Model projections of the North Atlantic thermohaline circulation for the 21st century assessed by observations. Geophysical Research Letters, 32, L23710.

• Teller, J.T. and D.W. Leverington, 2004. Glacial Lake Agassiz: A 5000 yr history of change and its relationship to the d18O record of Greenland. GSA Bulletin, 116, 729-742.

Gregory JM et al, 2005