December 2002

Section 2Section 2

Past ChangesPast Changesin Climatein Climate

Global surface temperatures are rising

Relative to 1961-90 average temperature

However, developing reliable long term climate trends is a challenge that must deal with many sources of measurement error

Ship data

Automated buoys

- 3

- 2

- 1

0

1

2

3

1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Year

°C

1943

Annual adjustment = 1.1°C

Effects of station relocations and other biases must be corrected

Mont Joli, Quebec

1950 1960 1970 1980 1990

Year

-0.5

-0.3

-0.1

0.1

0.3

0.5

Deg

rees

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

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

Global mean combined land/ocean Temperature, including error margin

Source: IPCC(2001)

On decadal time scales, surface and tropospheric behaviour can differ

Less so on multi-decadal times scales

Departures from the 1951-1980 average

1950 1960 1970 1980 1990 2000

Year

0

1

2

3

-1

-2

Tem

pera

ture

Chang

e (

deg

ress C

)Canadian temperatures have also increased substantially during the past decade

Changes in temperature are unevenly distributed

Degrees C

Trends for 1950-98

Fall 2001 was the 18th consecutive

above normal season

Precipitation has increased in some parts of the world and decreased in othersTrends (%/century) in annual precipitation for 1900-2000

Insert figure

USAS. Canada

S.E. AustraliaFSU -westFSU - east

NorwayN. JapanS. JapanN. ChinaS. ChinaEthiopia

W. KenyaSW S. Africa

NatalNord-esteThailand

Reg

ion

0 5 10-5-10-15

Linear trends (%/decade)

Total Precip

Heavy precip

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

Canada is becoming wetter

Percent change in precipitation 1950-98

- 3

- 2

- 1

0

1

2

3

4

5

110°95°

80°

PD SI Trend

Sum m er (JJA ) Palm er D rought Severity Index (PD SI) T rends 1925 - 1995

+ denotes sta tistica l s ign ificance a t 95% leve l

However, summers in some parts of North America have become much drier

Summer Palmer Drought Severity trends for 1925-95

+ indicates 95% significance

Paleo records suggest dry periods have been common in central North America in the past

Salinity Trends for Moon Lake, S.D.WET

DRY

1920 1940 1960 1980 2000 2020

Year

0

20

40

60

80

-20

-40

-60

-80

-100

Change in water levels (cm)

Lake Erie

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

73.00

73.50

74.00

74.50

75.00

75.50

76.00

1918 1928 1938 1948 1958 1968 1978 1988 1998

Year

Metres ASL

Lake Ontario water levels are now less variable due to flow controls

John Walsh – U. Illinois

Arctic spring snow cover has been declining rapidly

2.0

1.0

0

-1.0

-2.0

1960 1970 1980 1990 2000

Std

. A

no

mal

y fo

r F

eb-J

uly

rel

ati

ve

to 1

961-

90

Year

Chukchi Cap

Beaufort Sea

Canada basin

North Pole

Nansen Basin

Eastern Arctic

Location

0 1 2 3 4 5

Draft (Meters)

'58-'76

'93-'97

Arctic sea ice has become much thinner

Arctic Ocean sea ice is becoming less extensive

The decline in sea ice extent is unprecedented in at least the past century

Annual Mean

Arctic melt seasons are becoming longer

1980 19901985 1995Year

Nu

mb

er o

f m

elt

da

ys

80

70

50

60

A variety of indicators show a changing Arctic climate

1998 is particularly unusual

Trends in heavy precipitation vary across Canada

Fraction of annual precipitation falling in heavy events (%/yr)

1940-95

º º

Canada is becoming “less cold”

Trend in 5th percentile of daily Tmin (Winters, 1900-1998)

= less extreme

= more extreme

X = statistically significant

Trend in number of cold spells (consecutive periods below 20th percentile)

--

++

The number of cold spells are also decreasing

Trend in number of frost days (1950-99)

The number of “frost days” are decreasing

El Nino - La Nina behaviour patterns have been changing

The frequency of intense North Atlantic hurricanes appears to vary considerably

Figure 4

1900 1920 1940 1960 1980 2000

Year

0

20

40

60

80

100

Northern Hemispheric intense winter storms appear to be occurring more frequently

Sto

rms

per

Win

ter

Changes in intense NH winter storms and temperatures correlate well

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

Monthly Average Salinity Anomalies at Ocean Station P

The NE Pacific has become less saline

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

The North Atlantic Oscillation Index is also linked to regional climates, and has increased

Winter NAO1947-97

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 decrease1-3 cm/yr decrease

2-6 cm/yr increase2-6 cm/yr increase

Physical and Ecological Systems around the world are beginning to change

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

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

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