1. PALEOCLIMATE IMPLICATIONS FOR RECENT HUMAN INFLUENCE ON CLIMATE
Michael E. Mann
Department of Environmental Sciences
University of Virginia
World Federation of Scientists
August 22, 2003

2. CO2 Concentration
Measurements of CO2 in parts per million (ppm) at Mauna Loa Observatory.

3. Greenhouse Gases and
Warming
CO2
Related?

4. PALEOCLIMATOLOGY

5. PALEOCLIMATOLOGY

6. PALEOCLIMATOLOGY

7. Modeled Internal Natural Variability
Observations

8. PALEOCLIMATE ‘PROXY’ DATA

9. TREE RINGS

10. CORALS

11. ICE CORES

12. VARVED LAKE SEDIMENTS

13. HISTORICAL DOCUMENTS

14. Annual Resolution Proxy Climate Indicators
INSTRUMENTAL TEMPERATURE RECORD
GLOBAL PROXY CLIMATE RECORDS

15. Reconstructed Surface Temperatures
Mann, M.E., Bradley, R.S., Hughes, M.K., Global-Scale Temperature Patterns and Climate Forcing Over the Past Six Centuries, Nature, 392, , 1998.

16. Reconstructed Surface Temperatures
Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001

17. Temperature Proxy Climate Indicators
Past two millennia…
Mann, M.E., Jones, P.D., Global Surface Temperatures over the Past Two Millennia, Geophysical Research Letters, in press, 2003.

18. Temperature Proxy Climate Indicators
Past two millennia…
Mann, M.E., Ammann, C., Bradley, R.S., Briffa, K., Crowley, T.J., Hughes, M.K., Jones, P.D., Oppenheimer, M., Osborn, T.J., Overpeck, J.T., Rutherford, S., Trenberth, K.E., Wigley, T.M.L., On Past Temperatures and Anomalous late 20th Century Warmth, Eos, in press, 2003.

19. Northern Hemisphere Reconstructed Surface Temperatures
Past two millennia…
Northern Hemisphere
Mann, M.E., Jones, P.D., Global Surface Temperatures over the Past Two Millennia, Geophysical Research Letters, in press, 2003.

20. Northern Hemisphere Reconstructed Surface Temperatures
Past two millennia…
Northern Hemisphere
Mann, M.E., Jones, P.D., Global Surface Temperatures over the Past Two Millennia, Geophysical Research Letters, in press, 2003.

21. Reconstructed Surface Temperatures
Mann, M.E., Jones, P.D., Global Surface Temperatures over the Past Two Millennia, Geophysical Research Letters, in press, 2003.

22. Reconstructed Surface Temperatures
Mann, M.E., Jones, P.D., Global Surface Temperatures over the Past Two Millennia, Geophysical Research Letters, in press, 2003.

23. Natural CLIMATE FORCINGS Volcanism Solar
1000
1200
1400
1600
1800
2000
Volcanism
Solar
Natural
Crowley, T.J., Causes of Climate Change Over the Past 1000 Years, Science, , 2000.

24. Anthropogenic CLIMATE FORCINGS Industrial Aerosols Greenhouse Gases
Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001

25. Mann, M.E., The Value of Multiple Proxies Science, 297, 1481-1482, 2002.

26. Mann, M. E. , Ammann, C. , Bradley, R. S. , Briffa, K. , Crowley, T. J
Mann, M.E., Ammann, C., Bradley, R.S., Briffa, K., Crowley, T.J., Hughes, M.K., Jones, P.D., Oppenheimer, M., Osborn, T.J., Overpeck, J.T., Rutherford, S., Trenberth, K.E., Wigley, T.M.L., On Past Temperatures and Anomalous late 20th Century Warmth, Eos, in press, 2003.

27. Future Surface Temperatures Trends?
Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001

28. CONCLUSIONS
Comparisons between different proxy-based estimates, model predictions, and optimally- determined borehole estimates of past hemispheric SAT trends indicate broad consistency over the past millennium.
The latest results indicate that late 20th warmth appears unprecedented over at least the past two millennia for the Northern Hemisphere; conclusions for the Southern Hemisphere and globe are presently indeterminate.