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Southern Hemisphere Climate Change

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Title: Southern Hemisphere Climate Change


1
Southern Hemisphere Climate Change
Professor Matthew England Climate and
Environmental Dynamics Laboratory School of
Mathematics, Faculty of Science The University of
New South Wales
2
Outline
  • Observed 20th Century changes in the Southern
    Hemisphere climate system
  • Temperature
  • Rainfall
  • Land ice, ice shelves, and sea-ice
  • Ocean properties
  • Winds and extratropical weather systems
  • Projected changes

3
Increase in Atmospheric CO2 Since the Beginning
of the Industrial Era
4
CO2 Concentration is Rising
2000
1000
1200
1600
1800
1400
5
Radiative forcing in year 2000 relative to
pre-industrial
6
NH air temperatures since 1000 A.D.
7
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9
Is the Southern Ocean changing?
observations
Larsson-B Ice Shelf Collapse 31 January to 7
March 2002
http//nsidc.org/iceshelves/larsenb2002/animation.
html
10
West Antarctic Ice Sheet
Oppenheimer (Nature 1998)
11
Twentieth Century Land-Ice Changes
Davis et al., Vaughan Science, 2005
12
Melting of the Greenland Ice-sheet
13
Arctic Sea-ice melting
1990
2000
  • 10 decrease in sea-ice per decade

14
Ice Age Climate
Todays Climate
15
Antarctic Bottom Water
16
Rintoul 2006
17
0.017 psu
Rintoul 2006
18
.015
.008
.009
Rintoul 2006
19
Causes of fresher shelf water
  • Increased glacial ice melt?
  • More precipitation?
  • Less sea ice formation?
  • Change in winds and ocean circulation?

Davis et al., Vaughan Science, 2005
20
Intermediate depth waters in both hemispheres
have become cooler and fresher in recent decades.
Wong et al., 1999
21
Observations of temperature at intermediate
depths show a greater than expected warming at
high latitudes and a cooling at mid-latitudes of
the Southern Ocean over the last 50 years (Gille
2002).
22
Australian rainfall trend, 1950 present day
23
Australian temperature trend, 1950 present day
24
Southern Hemisphere Jet Stream
25
Changing Southern Hemisphere climate the
Southern Annular Mode
Sen Gupta England 2006
26
Southern Annular Mode
27
Roaring Forties / Furious Fifties
28
Southern Annular Mode
29
Southern Annular Mode
trend due to ozone delpletion greenhouse gas
increases
30
Northern Annular Mode
31
Regression of the Southern Annular Mode onto
rainfall
Observed
Model
Sen Gupta England 2006
32
July Zonal Wind (200 hPa)
1949-1968 1975-1994 difference
Pandora Hope IOCI
33
How much will the Southern Hemisphere change in
the future?
models
34
Climate Modelling
Governing equations
Forcing conditions
Initial conditions
Model output
35
Models of the ocean and atmosphere
  • Solve governing equations over a discrete grid
  • Use (sparse) observations in forcing functions
  • Integrate solutions forward in time
  • Assess simulation vs. observed fields

36
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37
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38
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39
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40
The Past and the Future
  • Instrumental Data
  • Proxy Reconstructions
  • Model Simulations

?T
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
1000
2000
1500
500
Year
41
Climate change appears to be buffered by the
Southern Ocean THC
Annual-mean temperature change predicted for
the year 2050 in the GFDL coupled climate model
experiment (Manabe et al. 1989).
42
Annual-mean temperature change predicted for
2070-2100 in IPCC Third Assessment Report models
Annual mean change in temperature (colour
shading) and its range (isolines) (Unit C) for
the SRES scenario A2, showing the period 2071 to
2100 relative to the period 1961 to 1990.
43
Climate Change simulation to year 2054
44
CONTROL
2050
Figure 1. Model Simulation of Trend in Hurricanes
(from Knutson et al, 2004)
45
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46
CONCLUSIONS
  • The Southern Hemisphere, like the antipodes,
    have undergone substantial climate change in the
    past century
  • A manifestation of climate change can be easily
    found in Southern Hemisphere air temperatures,
    rainfall, ocean properties, land-ice, sea-level,
    winds, and storm tracks
  • Models suggest these changes will continue for
    centuries even with relatively aggressive
    response strategies

47
Southern Hemisphere Climate Change
Professor Matthew England Climate and
Environmental Dynamics Laboratory School of
Mathematics, Faculty of Science The University of
New South Wales
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