1. December 2002 Section 2 Past Changes in Climate

2. Global surface temperatures are rising Relative to 1961-90 average temperature

3. However, developing reliable long term climate trends is a challenge that must deal with many sources of measurement error Ship data Automated buoys

4. 1943 Annual adjustment = 1.1°C Effects of station relocations and other biases must be corrected Mont Joli, Quebec

5. 19501960197019801990 Year -0.5 -0.3 -0.1 0.1 0.3 0.5 D e g r e e s C Source: Peterson et al. 1999. Rural Data Set (2290 Stations) Full Data Set (7280 Stations) Stations with large urbanization effects must be removed from the data base

6. Model studies suggest that SST corrections for systematic errors have significantly improved the quality of the record

7. Global mean combined land/ocean Temperature, including error margin Source: IPCC(2001)

8. On decadal time scales, surface and tropospheric behaviour can differ

9. Less so on multi-decadal times scales

10. Canadian temperatures have also increased substantially during the past decade

11. Changes in temperature are unevenly distributed Degrees C Trends for 1950-98

12. Fall 2001 was the 18 th consecutive above normal season

13. Precipitation has increased in some parts of the world and decreased in others Trends (%/century) in annual precipitation for 1900-2000 Insert figure

14. In many regions, changes in total precipitation are linked to changes in heavy precipitation

15. Canada is becoming wetter Percent change in precipitation 1950-98

16. However, summers in some parts of North America have become much drier Summer Palmer Drought Severity trends for 1925-95 + indicates 95% significance

17. Paleo records suggest dry periods have been common in central North America in the past Salinity Trends for Moon Lake, S.D. WET DRY

18. Water levels in the Great Lakes vary considerably, and are currently decreasing

19. Year Metres ASL Lake Ontario water levels are now less variable due to flow controls

20. John Walsh – U. Illinois Arctic spring snow cover has been declining rapidly 2.0 1.0 0 -2.0 19601970198019902000 Std. Anomaly for Feb-July relative to 1961-90 Year

21. Arctic sea ice has become much thinner

22. Arctic Ocean sea ice is becoming less extensive

23. The decline in sea ice extent is unprecedented in at least the past century Annual Mean

24. Arctic melt seasons are becoming longer 1980199019851995 Year Number of melt days 80 70 50 60

25. A variety of indicators show a changing Arctic climate 1998 is particularly unusual

26. Trends in heavy precipitation vary across Canada Fraction of annual precipitation falling in heavy events (%/yr) 1940-95 ºº

27. Canada is becoming “less cold” Trend in 5 th percentile of daily T min (Winters, 1900-1998) = less extreme = more extreme X = statistically significant

28. Trend in number of cold spells (consecutive periods below 20 th percentile) -+ The number of cold spells are also decreasing

29. Trend in number of frost days (1950- 99) The number of “frost days” are decreasing

30. El Nino - La Nina behaviour patterns have been changing

31. The frequency of intense North Atlantic hurricanes appears to vary considerably

32. Figure 4 190019201940196019802000 Year 0 20 40 60 80 100 Northern Hemispheric intense winter storms appear to be occurring more frequently Storms per Winter

33. Changes in intense NH winter storms and temperatures correlate well

34. Coral data from south-central Pacific also show significant ocean warming

35. Monthly Average Salinity Anomalies at Ocean Station P The NE Pacific has become less saline

36. Trends in NH surface air temperatures appear to be linked to the Arctic Oscillation Index

37. The North Atlantic Oscillation Index is also linked to regional climates, and has increased Winter NAO 1947-97

38. Winter North Atlantic wave heights have increased in the northeast and decreased at mid-latitudes Significant wave height trend pattern (1958-97) 1-3 cm/yr decrease 2-6 cm/yr increase

39. Physical and Ecological Systems around the world are beginning to change

40. Global costs of natural disasters are rising Insured losses (Constant US Dollars, 2000 values) Economic losses (Constant US Dollars, 2000 values) - - - - -Trend of economic losses _____ Trend of insured losses Economic losses from great natural catastrophes worldwide

41. There has also been a 10-fold increase in North American natural disaster losses

42. Current NH temperatures are very unusual within at least the past 1000 years