Teaching the Science of Climate Change

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Teaching the Science of Climate Change
Keith Burrows AIP Education Committee STAVCON
November 2007
This ppt available on www.vicphysics.org -
Teachers
Please read the Notes pages for more info
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A declaration of vested interests

• This presentation is dedicated to our wonderful
  grandchildren and all the others who will
  inherit the results of our efforts in this decade
  the last that has the option to act to avoid
  dangerous climate change.

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Overview

• Climate science
• Earths energy balance
• Interactions between emr and the atmosphere
• The effect of changes in the system
• Human induced changes
• The release of millions of years of stored energy
• Is the climate changing?
• How can we understand it?
• Climate models and their predictions.
• What can we do?
• Fossil fuels
• Reduce energy use
• Lower CO2 options
• Sustainable options
• The human response
• Sceptics, deniers, avoiders
• Change the light bulbs
• The need for real change
• Education

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Climate science

• Earths energy balance
• The average temperature of the Earth is
  determined by the balance between incoming solar
  radiation and outgoing heat radiation

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Climate science

• 1/3 reflected
• 2/3 absorbed then re-radiated as IR emr.
• 175,000 TW in
• 175,000 TW out

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Climate science

• Earths energy balance
• The average temperature of the Earth is
  determined by the balance between incoming solar
  radiation and outgoing heat radiation
• Not all the IR radiation from the surface escapes
  immediately...
• or the average temperature would be about 15ºC
• and there would be much greater swings between
  nightday, cloudno cloud

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Climate science

• Earths energy balance

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Climate science

• Earths energy balance
• The average temperature of the Earth is
  determined by the balance between incoming solar
  radiation and outgoing heat radiation
• Not all the IR radiation from the surface escapes
  immediately...
• or the average temperature would be about 15ºC
• and there would be much greater swings between
  nightday, cloudno cloud
• The Greenhouse effect
• Natural
• Water vapour
• Carbon dioxide
• Human produced
• Carbon dioxide
• Methane etc.

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Climate science

• Interactions between emr and the atmosphere EMR
• Blackbody spectra. All objects at ANY temperature
  emit emr
• Hot metal emits lots of shorter IR and some
  visible

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Climate science

• Interactions between emr and the atmosphere EMR
• Blackbody spectra. All objects at ANY temperature
  emit emr
• Cold objects only long IR and no visible
• Slightly shorter IR

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Climate science

• Interactions between emr and the atmosphere EMR
• Blackbody spectra
• Spectra of stars
• or anything else that hot

UV Vis IR
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Climate science

• Interactions between emr and the atmosphere EMR
• Blackbody spectra
• Sun and Earth
• but note that
• Earth is less than
• a millionth of
• the Sun

UV Vis short IR long IR
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Climate science

• Interactions between emr and the atmosphere EMR
• Types of spectra
• Blackbody continuous spectrum

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Climate science

• Interactions between emr and the atmosphere EMR
• Types of spectra
• Emission line spectrum

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Climate science

• Interactions between emr and the atmosphere EMR
• Types of spectra

This is what we are interested in.
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Climate science

• Interactions between emr and the atmosphere EMR
• First we need to know something about emr
  (light).
• Quantum physics tells us that it comes as
  photons
• Heres a red one
• Heres a violet one
• Notice that the red one has a longer wavelength
• It also has less energy
• (Violet is more violent!)

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Climate science

• Interactions between emr and the atmosphere EMR
• First we need to know something about emr
  (light).
• Quantum physics tells us that it comes as
  photons
• Heres an ultraviolet (UV) one
• Heres an infrared (IR) one
• Notice that the IR one has a longer wavelength
  again
• It also has much less energy
• but its IR that is of interest to us

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Climate science

• Interactions between emr and the atmosphere EMR
• The gases in the atmosphere absorb, and then
  re-radiate some parts of the spectrum but not
  others.
• The structure of the molecule determines what
  sort of energy is absorbed.
• Oxygen and Nitrogen molecules are tight and it
  takes a lot of energy to shake them.
• IR goes right past
• High energy UV can give its energy to oxygen
• but theres very little of that even in sunlight

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Climate science

• Interactions between emr and the atmosphere EMR
• The gases in the atmosphere absorb, and then
  re-radiate some parts of the spectrum but not
  others.
• The structure of the molecule determines what
  sort of energy is absorbed.
• H2O and CO2 molecules (and other GHGs) are more
  floppy
• IR gives them energy
• Which they re-radiate in random directions
• So some goes back down to Earth
• keeping us warmer
• The Greenhouse effect!

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Climate science

• The effect of changes
• Remember we wouldnt be here without it!
• Water vapour is the main GHG
• But what if we add more CO2?

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Climate science

• The effect of changes Feedback and Forcing
• More CO2 ? more warmth ? more H2O (evaporation) ?
  more warmth ? more H2O ? more warmth ? ???
• Water vapour goes in and out of the atmosphere
  very quickly
• Carbon dioxide is there for 100 years
• That makes a big difference in the way they act
• Adding H2O is not a problem.

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Climate pseudo science

• The effect of changes Feedback and Forcing

the combined effect of these greenhouse gases is
to warm Earth's atmosphere by about 33 ºC, from a
chilly -18 ºC in their absence to a pleasant 15
ºC in their presence. 95 (31.35 ºC) of this
warming is produced by water vapour, which is far
and away the most important greenhouse gas. The
other trace gases contribute 5 (1.65 ºC) of the
greenhouse warming, amongst which carbon dioxide
corresponds to 3.65 (1.19 ºC). The human-caused
contribution corresponds to about 3 of the total
carbon dioxide in the present atmosphere, the
great majority of which is derived from natural
sources. Therefore, the probable effect of
human-injected carbon dioxide is a miniscule
0.12 of the greenhouse warming, that is a
temperature rise of 0.036 ºC. Put another way,
99.88 of the greenhouse effect has nothing to do
with carbon dioxide emissions from human
activity. Prof. Bob Carter, Research Professor
at James Cook University, palaeontologist,
stratigrapher, marine geologist and environmental
scientist.
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Climate pseudo science

• The effect of changes Feedback and Forcing
• In short
• GHE ? 31C
• H2O ? 95
• OGHG ? 5 of which CO2 ? 3.6
• Human CO2 is 3 of CO2 so 0.1 of GHE
• ie. 0.04C No worries ?

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Climate pseudo science

• The effect of changes Feedback and Forcing
• Sounds impressive if only but ?
• www.realclimate.org A group of real climate
  scientists who try to help people like Carter
  and us.

RealClimate.org Gavin A. Schmidt climate
modeller at the NASA Goddard Institute for Space
Studies Dr. Michael E. Mann Penn State
University Departments of Meteorology and
Geosciences and the Earth and Environmental
Systems Institute, IPCC lead author Dr. Caspar
Ammann National Center for Atmospheric Research
(NCAR). Dr. Rasmus E. Benestad Norwegian project
called RegClim, Norwegian Meteorological
Institute Prof. Raymond S. Bradley Director of
the Climate System Research Center University of
Massachusetts, Ray Bradley Advisor to U.S.,
Swiss, Swedish, and U.K. National Science
Foundations, NOAA, IPCC, IGBP, Stockholm. William
M. Connolley Climate modeller with the British
Antarctic Survey. Prof. Stefan Rahmstorf New
Zealand Oceanographic Institute, Institute of
Marine Science in Kiel, Potsdam Institute for
Climate Impact Research in Germany, IPCC. Dr.
Eric Steig Isotope geochemist, University of
Washington Dr. Thibault de Garidel Institute of
Marine and Coastal Sciences at Rutgers
University. Dr. David Archer Computational ocean
chemist at the University of Chicago.
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Climate pseudo science

• The effect of changes Feedback and Forcing
• 95 should actually be 90-95 and is for clouds
  also.
• Cant simply subtract leaving 5-10 for GHGs.
• H2O and CO2 absorb different parts of the IR
  radiation.

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Climate pseudo science

• The effect of changes Feedback and Forcing
• Take away all H2O OGHGs absorb 34
• Take away OGHGs H2O absorb 85
• So effect of H2O 66 85
• Not a linear problem!
• So 5 for OGHGs should be 15 34
• CO2 on its own 9 26 ? ?T 3 to 9C
• (But that assumes Carters linearity which it
  isnt)

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Climate pseudo science

• The effect of changes Feedback and Forcing
• Reminder Carters figures
• GHE ? 31C
• H2O ? 95
• OGHG ? 5 of which CO2 ? 3.6
• Human CO2 is 3 of CO2 so 0.1 of GHE
• ie. 0.04C No worries ?

?
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Climate pseudo science

• The effect of changes Feedback and Forcing
• Anthropogenic CO2 is NOT 3!

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Climate pseudo science

• The effect of changes Feedback and Forcing
• Anthropogenic CO2 300 ppm ? 380 ppm
• Rise of 30
• linear extrapolation AGHG ? 1 to 2.6C
• (AGHG Anthropogenic GHGs)

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Climate science

• The effect of changes Feedback and Forcing
• Carter ignores complex mechanisms of the GHE.
  Assumes effects are linear Just plain wrong.
• Overlaps gases absorb overlapping wavelengths.
• Saturation more gas makes no difference.
• Feedback Particularly important. Positive and
  negative.
• Positive feedback

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Climate science

• The effect of changes Feedback and Forcing
• Examples of feedback
• Increased water vapour ? more clouds
• reflect sunlight (negative feedback)
• trap IR radiation (positive feedback)

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Climate science

• The effect of changes Feedback and Forcing
• Water vapour is a feedback GHG
• CO2, CH4, O3 etc are forcing agents
• They stay in the atmosphere whatever and force
  more heat into the climate system.
• Effect measured by Radiative forcing constant
• or the extra heat flowing into (or out of) the
  climate system as a result of a change in some
  part of the system

"The radiative forcing of the surface-troposphere
system due to the perturbation in or the
introduction of an agent (say, a change in
greenhouse gas concentrations) is the change in
net (down minus up) irradiance (solar plus
long-wave in Wm-2) at the tropopause AFTER
allowing for stratospheric temperatures to
readjust to radiative equilibrium, but with
surface and tropospheric temperatures and state
held fixed at the unperturbed values". (IPCC)
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Climate science

• The effect of changes Feedback and Forcing
• Computer models are the only way of taking all
  this into account a little later.

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Overview

• Climate science
• Earths energy balance
• Interactions between emr and the atmosphere
• The effect of changes in the system
• Human induced changes
• The release of millions of years of stored energy
• Is the climate changing?
• How can we understand it?
• Climate models and their predictions.
• What can we do?
• Fossil fuels
• Reduce energy use
• Lower CO2 options
• Sustainable options
• The human response
• Sceptics, deniers, avoiders
• Change the light bulbs
• The need for real change
• Education

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Human induced changes

• The release of solar energy and carbon stored
  over 100 million years ...

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Human induced changes

• The release of solar energy and carbon stored
  over 100 million years in only 100s of years
• We have to ask
• whether it might have
• an effect!

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Human induced changes

• Is the climate changing?

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IPCC SynRep
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Human induced changes

• Is the climate changing?

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Human induced changes

• Is the climate changing?

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Human induced changes

• Is the climate changing?

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Human induced changes

• We now know it has

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Human induced changes

• Is the climate changing?

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Human induced changes

• Is the climate changing?

IPCC SynRep
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Human induced changes

• Is the climate changing?

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IPCC SynRep
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IPCC SynRep
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Human induced changes

• How can we understand it?
• Its all a matter of physics!

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IPCC SynRep