Climate Change: Observations

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Climate Change Observations Predictions

• Presenter Neil Plummer
• National Climate Centre
• Lead Author Dr Scott Power
• Bureau of Meteorology Research
• Centre
• Acknowledgments Richard Whitaker, Phil Reid and
  other NCC colleagues

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Summary

• The worlds climate varies - decadal and longer
• The world has warmed up, sea-level has risen
• Is warming due to humans?
• How do climate models work?
• How warm will the world get?
• How high will sea-level rise?
• Observations - past future - crucial

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What causes climate change? Variations in the
suns output Large meteorite impact
Variations on the Earths orbit (Milutin
Milankovitch) Variations in ocean currents
Volcanoes (Mt. Tambora 1815) Variations in the
chemical composition of the atmosphere (human
impact?)
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Observing the climate system
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How do we know what past climates were like? -
Weve only been taking measurements for about
the last 300 years or so. We use so called
proxy indicators - interpretation of a range of
naturally occurring phenomena that are weather
sensitive
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Global issues Networks
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Global GCOS issues

• Pacific Island GCOS
• Networks
• GSN, GUAN, GAW, various terrestrial
• Poor collection rates for CLIMAT and CLIMAT TEMP
• Poor collection rates for daily and hourly
  historical data, including metadata
• Data Management
• Databases, data rescue
• Training workshop, Bureau of Met, Melbourne, 29
  November to 3 December

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Global Temperature Increase
Increased volcanism and decreased solar output
Decreased volcanism and increased solar output
Greenhouse
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Global Temperature Increase
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Decadal Variability
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Annual Streamflow into Perth water supply system,
1911-99
50 decline
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Summary Observed Global Climate Changes

• Warming greater over land than oceans
• Minimum temperatures increased more than maximum
  temperatures
• Decreases in cold extremes, weaker increases in
  hot extremes
• Weak increases in precipitation and cloud
• Slight increases in heavy precipitation events

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and more

• Ocean surface and subsurface warming
• Lowest 8 km of the atmosphere warming since at
  least 1958
• Sea level rise of 10-20 cm since 1900
• Snow cover extent decreased
• Sea ice extent decreased
• Glaciers reducing in length and volume
• Animals, plants shifts in locations and seasonal
  behaviour

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Sources of Greenhouse gases

• Include
• Fossil fuel burning
• Land use change, including deforestation
• Biomass burning
• Cement production
• CFCs, HFCs, HCFCs,

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The Enhanced Greenhouse Effect

• There is new and stronger evidence that most of
  the warming over the last 50 years is
  attributable to human activities
  (Intergovernmental Panel on Climate Change (IPCC)
  Third Assessment Report 2001)
• Stabilisation of greenhouse gas concentrations
  in the atmosphere at a level that would prevent
  dangerous anthropogenic interference with the
  climate system
• (Article 2 of the United Nations Framework
  Convention on Climate Change)

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Future scenariosModelling the climate system
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Climate Model Uncertainties

• Climate system feedbacks
• - water vapour and clouds
• - ice and snow
• - land surface
• Deep ocean circulation
• Global carbon cycle
• Atmospheric chemistry
• Future emission scenarios

As scale decreases, uncertainty increases
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Climate forcing increase in CO2
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Regional variations in projections

• Temperature 2xCO2 transient control
• Bureau of Met. model
• Precipitation 2xCO2 transient control

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Projections of global temperature
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21st C sea-level projections (IPCC, 2001)
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Projections for 21st C

• Models suggest that
• 1.4-5.8 oC, 0.09-0.88 cm sea-level rise
• More rapid changes than occurred last century and
  rises are expected to continue beyond the coming
  century
• Fewer frosts cold days cold nights
• More hot days mild nights
• More heavy rainfall events

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Further Information

• IPCC Third Assessment Report 2001
• Greenhouse Effect and Climate Change booklet
• Australian State of Environment report
  (Atmosphere) 2001
• CSIRO Climate Change Projections for Australia
• www.bom.gov.au

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Irreversible Change?