2. Part IV: Historical Climate Changes Lecture 18: The Little Ice Age (Chapter 15)

3. Frequency of sea ice intrusion along the coast of Iceland MW: 1000-1300LIA: 1400-1900 Vikings invaded southwestern Greenland Vikings abandoned Greenland

4. Canada arctic lichen Dead lichen due to snow expansion indicates the time of LIA

5. Mountain glacier: Annual layer, δ 18 O, Dust content,

6. Ice core in Peruvian Andes MWLIA

7. Ice cores in four regions MW LIA Warming? Global? Temperature change, not uniform! MW and LIA seems to be present in tropical mountain glaciers, but not obvious in Greenland and Antarctic ice sheets

8. Tasmanian tree rings MW? LIA? Not obvious in SH Unprecedented warming?

9. Reconstructed NH temperature (hockey stick pattern) MW?LIA? Global warming?

10. Longest Instrument record LIA? Global warming?

11. Temperature stations, Urban heat island effect

12. Global surface temperature

14. Source: D. Fagre, USGS, 2004 Recession of the Grinnell Glacier “Glacier National Park” 1910 1997

15. Kilimanjaro ice extent (km 2 ) ?

16. Little Penck Glacier, Kilimanjaro

17. Sea level rise 5cm upper ocean warming, 3 cm land ice melting, 2 cm Greenland ice melting

19. Increased cloud cover Unclear warming or cooling effect because unknown high or low clouds

20. Arctic sea ice Arctic clouds (warming or cooling?)

21. The growing season lengthens in Alaska

22. Tree Ring Width Obs. Trend Tree ring Tair Model Obs. P ~ R

23. Global Greening Trend Global Greening Trend Total CO2 Physiology Carbon fertilization Radiation Obs. >1980 Obs. – crops (FPAR: Fraction of Photosynthetically Active Radiation)

24. Decrease in snow cover

25. Reduced Arctic sea ice cover and thickness !

26. Global Lake Open/Close Date Lake Mendota

27. 2) Is it cause by orbital forcing of reduced summer insolation or millennial variability? Fundamental Questions on MW/LIA 1) Are these change regional or global? 3) What caused the rapid warming since 1900 that terminates the LIA?

28. Forcing mechanism for centennial and decadal variability Solar forcing Natural variability: PDO, NAO

29. 11 year cycle: solar radiation and sunspots

30. More Sunspots More solar radiation from faculae

31. Sunspot history from telescopes

32. Forcing mechanism for interannual variability Volcanic forcing Natural variability: ESNO Relation between ENSO and volcanic activity?

33. Eruption of Mount Pinatobo in 1991 and global cooling

34. (Tropical) Volcanic cooling

35. End of Lecture 19

36. Lecture 20: El Nino, La Nina and Southern Oscillation (Chapter 16)

37. Change of Climate Variability Tropical Pacific SST

40. El Nino and Southern Oscillation: ENSO

41. http://iri.columbia.edu/climate/ENSO/currentinfo/SST_table.html#figure

42. Historical record of El Nino

43. Corals and tropical ocean Annual layers made of CaCO3, take ocean water δ 18 O (a proxy of temperature, but also with salinity effect) LIA? El Nino

44. Evolution of the last 21,000 yrs Deglaciation, but not smooth

45. Change of Climate Variability Tropical Pacific SST

46. 1935 Texas (Dustbowl) 1997 Kansas

48. Global surface temperature

49. SAHEL RAINFALL North Africa Climate Change S. Nicholson Charney Charney ? SST decadal variability!

50. Global US Wisconsin Madison Climate Change: Global to Regional Perspective

51. End of Lecture 20

52. Tibet ice core

53. Tree-ring (dendroclimatology)

54. Arctic tree ring Asian tree ring Strong centennial /decadal variability

57. Natural Climate Variability