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