december 2002 section 2 past changes in climate. global surface temperatures are rising relative to...
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December 2002
Section 2Section 2
Past ChangesPast Changesin Climatein Climate
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Global surface temperatures are rising
Relative to 1961-90 average temperature
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However, developing reliable long term climate trends is a challenge that must deal with many sources of measurement error
Ship data
Automated buoys
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- 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
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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
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Model studies suggest that SST corrections for systematic errors have significantly improved the quality of the record
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Global mean combined land/ocean Temperature, including error margin
Source: IPCC(2001)
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On decadal time scales, surface and tropospheric behaviour can differ
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Less so on multi-decadal times scales
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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
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Changes in temperature are unevenly distributed
Degrees C
Trends for 1950-98
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Fall 2001 was the 18th consecutive
above normal season
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Precipitation has increased in some parts of the world and decreased in othersTrends (%/century) in annual precipitation for 1900-2000
Insert figure
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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
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Canada is becoming wetter
Percent change in precipitation 1950-98
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- 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
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Paleo records suggest dry periods have been common in central North America in the past
Salinity Trends for Moon Lake, S.D.WET
DRY
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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
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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
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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
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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
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Arctic Ocean sea ice is becoming less extensive
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The decline in sea ice extent is unprecedented in at least the past century
Annual Mean
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Arctic melt seasons are becoming longer
1980 19901985 1995Year
Nu
mb
er o
f m
elt
da
ys
80
70
50
60
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A variety of indicators show a changing Arctic climate
1998 is particularly unusual
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Trends in heavy precipitation vary across Canada
Fraction of annual precipitation falling in heavy events (%/yr)
1940-95
º º
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Canada is becoming “less cold”
Trend in 5th percentile of daily Tmin (Winters, 1900-1998)
= less extreme
= more extreme
X = statistically significant
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Trend in number of cold spells (consecutive periods below 20th percentile)
--
++
The number of cold spells are also decreasing
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Trend in number of frost days (1950-99)
The number of “frost days” are decreasing
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El Nino - La Nina behaviour patterns have been changing
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The frequency of intense North Atlantic hurricanes appears to vary considerably
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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
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Changes in intense NH winter storms and temperatures correlate well
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Coral data from south-central Pacific also show significant ocean warming
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Monthly Average Salinity Anomalies at Ocean Station P
The NE Pacific has become less saline
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Trends in NH surface air temperatures appear to be linked to the Arctic Oscillation Index
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The North Atlantic Oscillation Index is also linked to regional climates, and has increased
Winter NAO1947-97
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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
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Physical and Ecological Systems around the world are beginning to change
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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
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There has also been a 10-fold increase in North American natural disaster losses
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Current NH temperatures are very unusual within at least the past 1000 years