Southern Hemisphere Climate Change Professor Matthew England
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Transcript of Southern Hemisphere Climate Change Professor Matthew England
Southern Hemisphere Climate Southern Hemisphere Climate Change Change
Professor Matthew EnglandProfessor Matthew England
Climate and Environmental Dynamics Laboratory Climate and Environmental Dynamics Laboratory
School of Mathematics, Faculty of ScienceSchool of Mathematics, Faculty of Science
The University of New South WalesThe University of New South Wales
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
Increase in Atmospheric CO2 Since the Beginning of the Industrial Era
CO2 Concentration is Rising
190
290
1959
2004
1000 1200 1400 1600 1800 2000
Radiative forcing in year 2000 relative to pre-industrial
NH air temperatures since 1000 A.D.
Is the Southern Ocean changing?… observations
Larsson-B Ice Shelf Collapse 31 January to 7 March 2002
http://nsidc.org/iceshelves/larsenb2002/animation.html
Oppenheimer (Nature 1998)
West Antarctic Ice Sheet
Twentieth Century Land-Ice Changes
Davis et al., Vaughan; Science, 2005
Melting of the Greenland Ice-sheet
Arctic Sea-ice melting
1990
2000
~10% decrease in sea-ice per decade
Today’s Climate
Ice Age Climate
Antarctic Bottom WaterAntarctic Bottom Water
Rintoul 2006
34.655 34.66 34.665 34.67 34.675 34.68 34.685 34.69 34.695
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
SALINITY
TH
ET
A115E, 61S to 63.3S
28.27
28.30 28.35
1995
2005
0.017 psu
Rintoul 2006
34.64 34.65 34.66 34.67 34.68 34.69 34.7 34.71 34.72 34.73 34.74
-0.5
0
0.5
128.27 28.3 28.35
SALINITY
TH
ET
A115E, 56.5S to 61S
28.27
28.3028.35
1970
19952005
.008
.009
.015
Rintoul 2006
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
Wong et al., 1999
Intermediate depth waters in both hemispheres have become cooler and fresher in recent decades.
Figure 3 from Gille, S. T., 2002. Warming of the Southern Ocean since the 1950s. Science, 295, 1275-1277.
Temperature trends between 700 and 1100 m depth from ALACE floats.
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).
Australian rainfall trend, 1950 – present day
Australian temperature trend, 1950 – present day
Changing Southern Hemisphere climate: the Southern Annular Mode
Sen Gupta & England 2006
Southern Annular Mode
Roaring Forties / Furious Fifties
Southern Annular Mode
Southern Annular Mode
… trend due to ozone delpletion & greenhouse gas increases
Northern Annular Mode
Regression of the Southern Annular Mode onto rainfall
Model ‘Observed’
Sen Gupta & England 2006
July Zonal Wind (200 hPa)
1949-1968 1975-1994 difference
Pandora Hope IOCI
How much will the Southern Hemisphere change in the future?
… models
Climate Modelling
Governing equations
Forcing conditions
Initial conditions Model
output
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
1000 20001500500Year
The Past and the Future
Instrumental Data Proxy Reconstructions Model Simulations
2100
5.8
IPCC highand lowprojection
1.4
Spörerminimum
Maunderminimum
Daltonminimum
0
0.2
-0.2
-0.4
-0.6
0.4
∆T
-0.8
Annual-mean temperature change predicted for ~ the year 2050 in the GFDL coupled climate model experiment (Manabe et al. 1989).
Climate change appears to be buffered by the Southern Ocean THC
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.
Annual-mean temperature change predicted for 2070-2100 in IPCC Third Assessment Report models
Climate Change simulation to year 2054
Figure 1. Model Simulation of Trend in Hurricanes (from Knutson et al, 2004)
CONTROL
2050
• 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
CONCLUSIONS
Southern Hemisphere Climate Southern Hemisphere Climate Change Change
Professor Matthew EnglandProfessor Matthew England
Climate and Environmental Dynamics Laboratory Climate and Environmental Dynamics Laboratory
School of Mathematics, Faculty of ScienceSchool of Mathematics, Faculty of Science
The University of New South WalesThe University of New South Wales