1. Global Warming Michael E. Mann, Department of Environmental Sciences
University of Virginia
ESO Global Warming Forum
Department of Environmental Sciences, UVA
Feb 20, 2001

2. OVERVIEW
Observed Climate Change

3. OVERVIEW
Observed Climate Change
The Greenhouse Effect

4. OVERVIEW Observed Climate Change The Greenhouse Effect
Detecting and Attributing Climate Change

5. Observed Climate Change

7. 20th CENTURY TEMPERATURE TRENDS
TEMPERATURE ANOMALY (oC)

8. 1998 Global Temperature Pattern

9. EL NINO/SOUTHERN OSCILLATION (“ENSO”)
Substantial interannual climate variability associated with ENSO, but decadal variability is also evident as well. The recent decadal trend towards El Nino conditions could be natural or anthropogenic.
Multivariate ENSO Index (“MEI”)

10. NORTH ATLANTIC OSCILLATION
Negative Phase
Positive Phase

11. NORTH ATLANTIC OSCILLATION
Explains enhanced warming in certain regions of Northern Hemisphere in past couple decades

12. Pacific Decadal “Oscillation”

13. Atlantic Multidecadal Oscillation
There is evidence of multidecadal natural variability in the North Atlantic ocean circulation

14. The Greenhouse Effect

15. GREENHOUSE EFFECT?

17. ENHANCED GREENHOUSE EFFECT?

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

19. Greenhouse Gases and
Warming
CO2
Related?

20. Detecting and Attributing Climate Change

21. Intergovernmental Panel on Climate Change (United Nations), Third Assessment Report, 2001
`There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activity'

25. MANTRA OF PALEOCLIMATOLOGY

27. TREE RINGS

28. CORALS

29. ICE CORES

30. VARVED LAKE SEDIMENTS

31. HISTORICAL DOCUMENTS

32. Map showing global proxy climate network
Map showing global proxy climate network. All of the records date back to at least 1820, most to the early 18th century, and many back to Before 1400, the network is too sparse to constrain large-scale patterns of variability without greatly expanded uncertainties.

33. Warm In Europe  Warm in Northern Hemisphere!!
1791 El Nino
Warm In Europe  Warm in Northern Hemisphere!!

35. CLIMATE FORCINGS

36. CLIMATE FORCINGS

37. Science

38. CONCLUSIONS
“Anthropogenic” activity associated with increased greenhouse gas concentrations during the past two centuries
Recent global surface temperatures are unprecedented this century, and likely at least the past millennium
It is difficult to explain the recent surface warming in terms of natural climate variability
Recent surface warming is consistent with simulations of the effects of anthropogenic influence on climate
Given uncertainties, future projected climate changes vary from the modest to the dramatic