teaching the science of climate change

Teaching the Teaching the Science of Science of

Climate ChangeClimate Change

Keith Burrows

AIP Education Committee

STAVCON November 2007

Please read the Notes pages for more info

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A declaration of vested interestsA declaration of vested interests

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

OverviewOverview Climate scienceClimate science

– Earth’s energy balanceEarth’s energy balance– Interactions between emr and the atmosphereInteractions between emr and the atmosphere– The effect of changes in the systemThe effect of changes in the system

Human induced changesHuman induced changes– The release of millions of years of stored energyThe release of millions of years of stored energy– Is the climate changing?Is the climate changing?– How can we understand it? How can we understand it? – Climate models and their predictions.Climate models and their predictions.

What can we do?What can we do?– Fossil fuelsFossil fuels– Reduce energy useReduce energy use– Lower CO2 optionsLower CO2 options– Sustainable optionsSustainable options

The human responseThe human response– Sceptics, deniers, avoidersSceptics, deniers, avoiders– Change the light bulbsChange the light bulbs– The need for real changeThe need for real change

EducationEducation– That’s where we come inThat’s where we come in

ClimateClimate science science Earth’s energy balanceEarth’s energy balance

– The average temperature of the Earth is determined by the balance The average temperature of the Earth is determined by the balance between incoming solar radiation and outgoing ‘heat’ radiationbetween incoming solar radiation and outgoing ‘heat’ radiation

ClimateClimate science science ~ 1/3 reflected~ 1/3 reflected ~ 2/3 absorbed ~ 2/3 absorbed

then re-radiated then re-radiated as IR emr.as IR emr.

175,000 TW in175,000 TW in 175,000 TW out175,000 TW out



– Not all the IR radiation from the surface escapes immediately... Not all the IR radiation from the surface escapes immediately... – or the average temperature would be about – 15or the average temperature would be about – 15ºC ºC – and there would be much greater swings between night—day, and there would be much greater swings between night—day,

cloud—no cloudcloud—no cloud



– Not all the IR radiation from the surface escapes immediately... Not all the IR radiation from the surface escapes immediately... – or the average temperature would be about – 15or the average temperature would be about – 15ºC ºC – and there would be much greater swings between night—day, and there would be much greater swings between night—day,

cloud—no cloudcloud—no cloud

The Greenhouse effect:The Greenhouse effect:– Natural:Natural:

Water vapourWater vapour Carbon dioxideCarbon dioxide

– Human produced:Human produced: Carbon dioxideCarbon dioxide Methane etc.Methane etc.

ClimateClimate science science Interactions between emr and the atmosphere: EMRInteractions between emr and the atmosphere: EMR

– Blackbody spectra. All objects at ANY temperature emit emrBlackbody spectra. All objects at ANY temperature emit emr– Hot metal emits lots of shorter IR and some visibleHot metal emits lots of shorter IR and some visible


– Blackbody spectra. All objects at ANY temperature emit emrBlackbody spectra. All objects at ANY temperature emit emr– Cold objects only long IR and no visibleCold objects only long IR and no visible– Slightly shorter IRSlightly shorter IR


– Blackbody spectraBlackbody spectra– Spectra of starsSpectra of stars– or anything else that hotor anything else that hot

– UV Vis IR –


– Blackbody spectraBlackbody spectra– Sun and EarthSun and Earth

but note thatbut note that

Earth is less thanEarth is less than

a millionth of a millionth of

the Sunthe Sun

– UV Vis short IR – long IR


– Types of spectraTypes of spectra– Blackbody continuous spectrumBlackbody continuous spectrum


– Types of spectraTypes of spectra– Emission line spectrumEmission line spectrum


– Types of spectraTypes of spectra

This is what we are interested in.


– First we need to know something about emr (light).First we need to know something about emr (light).– Quantum physics tells us that it comes as ‘photons’Quantum physics tells us that it comes as ‘photons’– Here’s a red oneHere’s a red one– Here’s a violet oneHere’s a violet one– Notice that the red one has a longer wavelengthNotice that the red one has a longer wavelength– It also has less energyIt also has less energy– (Violet is more violent!)(Violet is more violent!)


– First we need to know something about emr (light).First we need to know something about emr (light).– Quantum physics tells us that it comes as ‘photons’Quantum physics tells us that it comes as ‘photons’– Here’s an ultraviolet (UV) oneHere’s an ultraviolet (UV) one– Here’s an infrared (IR) oneHere’s an infrared (IR) one– Notice that the IR one has a longer wavelength againNotice that the IR one has a longer wavelength again– It also has much less energy – It also has much less energy – – but it’s IR that is of interest to usbut it’s IR that is of interest to us


– The gases in the atmosphere absorb, and then re-radiate some The gases in the atmosphere absorb, and then re-radiate some parts of the spectrum but not others.parts of the spectrum but not others.

– The structure of the molecule determines what sort of energy is The structure of the molecule determines what sort of energy is absorbed.absorbed.

– Oxygen and Nitrogen molecules are ‘tight’ and it takes a lot of Oxygen and Nitrogen molecules are ‘tight’ and it takes a lot of energy to ‘shake’ them.energy to ‘shake’ them.

– IR goes right pastIR goes right past– High energy UV can give its energy to oxygenHigh energy UV can give its energy to oxygen– but there’s very little of that even in sunlightbut there’s very little of that even in sunlight


– The gases in the atmosphere absorb, and then re-radiate some The gases in the atmosphere absorb, and then re-radiate some parts of the spectrum but not others.parts of the spectrum but not others.

– The structure of the molecule determines what sort of energy is The structure of the molecule determines what sort of energy is absorbed.absorbed.

– HH22O and COO and CO22 molecules (and other GHGs) are more ‘floppy’ molecules (and other GHGs) are more ‘floppy’

– IR gives them energyIR gives them energy– Which they re-radiate – in random directionsWhich they re-radiate – in random directions– So some goes back down to EarthSo some goes back down to Earth– keeping us warmerkeeping us warmer– The Greenhouse effect!The Greenhouse effect!

C:\Documents and Settings\My Documents\KB-CCPresentation\Pics To use\Movies&Graphics\carbon-dioxide-greenhouse.mov

ClimateClimate science science The effect of changesThe effect of changes

– Remember we wouldn’t be here without it!Remember we wouldn’t be here without it!– Water vapour is the main GHGWater vapour is the main GHG

– But what if we add more COBut what if we add more CO22??

ClimateClimate science science The effect of changes – Feedback and ForcingThe effect of changes – Feedback and Forcing

– More COMore CO22 → more warmth → more H→ more warmth → more H22O (evaporation) O (evaporation)

→ more warmth → more H→ more warmth → more H22O → more warmth → ???O → more warmth → ???

– Water vapour goes in and out of the atmosphere very Water vapour goes in and out of the atmosphere very quicklyquickly

– Carbon dioxide is there for ~ 100 years Carbon dioxide is there for ~ 100 years – That makes a big difference in the way they actThat makes a big difference in the way they act

– Adding HAdding H22O is not a problem.O is not a problem.

ClimateClimate pseudopseudo science science The effect of changes – Feedback and ForcingThe 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.


– In short:– GHE → 31°C– H2O → 95%– OGHG → 5% of which CO2 → 3.6%– Human CO2 is 3% of CO2 so 0.1% of GHE

– ie. 0.04°C No worries ☺


– Sounds impressive – if only – but Sounds impressive – if only – but – www.realclimate.orgwww.realclimate.org A group of real climate scientists A group of real climate scientists

who try to help people like Carter – and us.who try to help people like Carter – and us.RealClimate.orgGavin A. Schmidt: climate modeller at the NASA Goddard Institute for Space StudiesDr. Michael E. Mann: Penn State University Departments of Meteorology and Geosciences and the Earth and Environmental Systems Institute, IPCC lead authorDr. Caspar Ammann: National Center for Atmospheric Research (NCAR).Dr. Rasmus E. Benestad: Norwegian project called RegClim, Norwegian Meteorological InstituteProf. 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 WashingtonDr. Thibault de Garidel: Institute of Marine and Coastal Sciences at Rutgers University.Dr. David Archer: Computational ocean chemist at the University of Chicago.

http://www.realclimate.org/

ClimateClimate pseudopseudo science science

The effect of changes – Feedback and ForcingThe effect of changes – Feedback and Forcing– 95% should actually be 90-95% and is for

clouds also.– Can’t simply subtract leaving 5-10% for GHGs.– H2O and CO2 absorb different parts of the IR

radiation.


– 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% → ΔT ~ 3 to 9°C– (But that assumes Carter’s linearity which it (But that assumes Carter’s linearity which it

isn’t)isn’t)


– Reminder – Carter’s figures:– GHE → 31°C– H2O → 95%– OGHG → 5% of which CO2 → 3.6%– Human CO2 is 3% of CO2 so 0.1% of GHE

– ie. 0.04°C No worries ☺

?


– Anthropogenic CO2 is NOT 3%!


– Anthropogenic CO2: 300 ppm → 380 ppm– Rise of 30% – linear extrapolation: AGHG → 1 to 2.6°C

(AGHG = Anthropogenic GHGs)

ClimateClimate science science The effect of changes – The effect of changes – FeedbackFeedback and Forcing 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:

ClimateClimate science science The effect of changes – The effect of changes – FeedbackFeedback and Forcing and Forcing

– Examples of feedback: – Increased water vapour → more clouds– reflect sunlight (negative feedback) – trap IR radiation (positive feedback)

ClimateClimate science science The effect of changes – The effect of changes – FeedbackFeedback and and ForcingForcing

– Water vapour is a ‘Water vapour is a ‘feedbackfeedback’ GHG’ GHG– CO2, CH4, O3 etc are ‘CO2, CH4, O3 etc are ‘forcingforcing’ agents’ agents– They stay in the atmosphere whatever and They stay in the atmosphere whatever and

‘force’ more heat into the climate system.‘force’ more heat into the climate system.– Effect measured by ‘Radiative forcing constant’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)

ClimateClimate science science The effect of changes – The effect of changes – FeedbackFeedback and and ForcingForcing

– Computer models are the only way of taking all Computer models are the only way of taking all this into account – a little later.this into account – a little later.

OverviewOverview Climate scienceClimate science

– Earth’s energy balanceEarth’s energy balance– Interactions between emr and the atmosphereInteractions between emr and the atmosphere– The effect of changes in the systemThe effect of changes in the system

Human induced changesHuman induced changes– The release of millions of years of stored energyThe release of millions of years of stored energy– Is the climate changing?Is the climate changing?– How can we understand it? How can we understand it? – Climate models and their predictions.Climate models and their predictions.

What can we do?What can we do?– Fossil fuelsFossil fuels– Reduce energy useReduce energy use– Lower CO2 optionsLower CO2 options– Sustainable optionsSustainable options

The human responseThe human response– Sceptics, deniers, avoidersSceptics, deniers, avoiders– Change the light bulbsChange the light bulbs– The need for real changeThe need for real change

EducationEducation– That’s where we come inThat’s where we come in

Human induced changesHuman induced changes The release of solar energy and carbon The release of solar energy and carbon

stored over 100 million years ...stored over 100 million years ...

Human induced changesHuman induced changes The release of solar energy and carbon The release of solar energy and carbon

stored over 100 million years in only 100’s of stored over 100 million years in only 100’s of yearsyears

We have to askWe have to ask

whether it might havewhether it might have

an effect!an effect!

Human induced changesHuman induced changes Is the climate changing? Is the climate changing?

IPCC SynRep

Human induced changesHuman induced changes Is the climate changing?Is the climate changing?

Human induced changesHuman induced changes We now know it has:We now know it has:


IPCC SynRep

Human induced changesHuman induced changes How can we understand it?How can we understand it?

– It’s all a matter of physics! It’s all a matter of physics!

IPCC SynRep

teaching the science of climate change

Documents

ir emr

emr light

ir radiation

climate models

incoming solar radiation

dangerous climate change

outgoing heat radiationnot

emrblackbody spectrasun