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
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