Climate Science Keith Burrows Science Teachers for Climate Awareness This presentation is designed...

Climate ScienceClimate Science

Keith Burrows

Science Teachers for Climate Awareness

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Climate Science Climate Science

and why we need to know about it.and why we need to know about it.

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The Big PictureThe Big Picture


MARS:MARS:Atmosphere: Atmosphere: Very thinVery thinMean temperature: Mean temperature: –65–65ooCC


MARS:MARS:Atmosphere: Atmosphere: Very thin COVery thin CO22

Mean temperature: Mean temperature: –65–65ooC (but –140C (but –140ooC to +20C to +20ooC )C )No significant greenhouse effectNo significant greenhouse effect


VENUS:VENUS:Atmosphere: Atmosphere: Thick Thick Mean temperature: Mean temperature: +464+464ooCC


VENUS:VENUS:Atmosphere: Atmosphere: Thick COThick CO22! !

Mean temperature: Mean temperature: +464+464ooCCA runaway greenhouse effect!A runaway greenhouse effect!

The Big PictureThe Big PictureEARTH:EARTH:Atmosphere: Atmosphere: NN22 , O , O22 , H , H22O and a little COO and a little CO22

Mean temperature: Mean temperature: +15+15ooCCJust right!Just right!

Why?

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

– Average temperature of the Earth: Average temperature of the Earth: – Balance between incoming solar radiation Balance between incoming solar radiation – and outgoing ‘heat’ radiation (IR)and outgoing ‘heat’ radiation (IR)

Temperature is a balance between Temperature is a balance between heat in heat in ... and heat out... and heat out

VisibleVisible and and Infrared Infrared (short wavelength)(short wavelength)

Infrared Infrared (long wavelength)(long wavelength)

Car temperature steady at Car temperature steady at 25°C25°C

25°C25°C

ClimateClimate science science

Visible inVisible in

IR out (same amount)IR out (same amount)

More heat in than out More heat in than out

– – car warming car warming 30°C 30°C

30°C30°C


IR out increasing (but less than in)

More visible inMore visible in

Heat in now same as heat outHeat in now same as heat out

– – temperature steady temperature steady 40°C40°C

40°C40°C


IR out increased IR out increased – – now same as innow same as in

Visible inVisible in

As things getter hotter they:As things getter hotter they: 1) Radiate more energy (as with the car)1) Radiate more energy (as with the car) 2) Get brighter and bluer 2) Get brighter and bluer

((infraredinfrared → → red red →→ yellowyellow →→ whitewhite →→ blueblue))


We We seesee the kettle by the kettle by reflected light – we can’t see reflected light – we can’t see the IR. But we can the IR. But we can feelfeel it. it.

Heat in now same as heat outHeat in now same as heat out

– – temperature steady temperature steady 40°C40°C


Climate scienceClimate science

Earth’s energy balanceEarth’s energy balance

So what determines the Earth’s temperature?So what determines the Earth’s temperature?

The balance between the energy coming inThe balance between the energy coming in ... ... and that going out.and that going out.


Both Both incomingincoming and and outgoingoutgoing energy radiation energy radiation can can varyvary over long time intervals. over long time intervals.

Or even quite short ones!Or even quite short ones!


That is what leads to That is what leads to CLIMATE CHANGECLIMATE CHANGE


Incoming sunlight Incoming sunlight varies with... varies with...

The Sun in UV light


Incoming sunlight Incoming sunlight varies with... varies with...

So what determines the Earth’s temperature?So what determines the Earth’s temperature? Incoming sunlight Incoming sunlight varies with... varies with...

~30%

90%+

So what determines the Earth’s temperature?So what determines the Earth’s temperature? Incoming sunlightIncoming sunlight also varies with... also varies with...

So what determines the Earth’s temperature?So what determines the Earth’s temperature? OutgoingOutgoing energy varies with... energy varies with...

1) How hot the Earth is

and...


2) ...how much energy is trapped by the atmosphere2) ...how much energy is trapped by the atmosphere

A little physicsA little physics Earth’s energy balanceEarth’s energy balance

– Two simple laws of physics Two simple laws of physics enable us to figure out the enable us to figure out the energy balance:energy balance: The The Stefan-Boltzmann law... Stefan-Boltzmann law...

I = εσT I = εσT44 Wien’s law... λWien’s law... λmaxmax = = 0.00290.0029/T/T

– S-B just tells us how much S-B just tells us how much heat a hot object radiates.heat a hot object radiates.

– Wien tells us what sort of Wien tells us what sort of radiation it will be.radiation it will be.

(but fortunately others have done the (but fortunately others have done the hard work for us!)hard work for us!)

A little physicsA little physics

Stefan-Stefan-Boltzmann Boltzmann is about is about intensityintensity

ClimateClimate science science Earth’s energy balanceEarth’s energy balance Svante August Arrhenius worked it out in 1896Svante August Arrhenius worked it out in 1896


“The Earth’s average temperature should be about –18oC”

?


“Ah! The atmosphere must be trapping the heat”


“But Oxygen and Nitrogen can’t absorb the infrared radiation”

?


“It must be the water vapour and carbon dioxide!”


“Together they absorb heat and re-emit enough back to Earth to raise the temperature by

+33degrees!”


“So what will all the CO2 we are putting in the atmosphere do?”

?


“If we double the CO2 it could raise the temperature by about 5 degrees!”

That’s not all that far That’s not all that far off modern estimatesoff modern estimatesIPCC: 2°C → 5°CIPCC: 2°C → 5°C

“That will make Sweden warmer – good !”

ClimateClimate science science Earth’s energy balance (sum up)Earth’s energy balance (sum up)

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

– Not all the IR radiation from the surface Not all the IR radiation from the surface escapes immediately... escapes immediately...

– or the average temperature would be a or the average temperature would be a freezing –18freezing –18ºC ºC

– No liquid water or cloudsNo liquid water or clouds– And no life!And no life!

Earth’s energy balance (sum up)Earth’s energy balance (sum up)– The average temperature of the Earth is The average temperature of the Earth is

determined by the balance between incoming determined by the balance between incoming solar radiation and outgoing ‘heat’ radiationsolar radiation and outgoing ‘heat’ radiation

– Not all the IR radiation from the surface Not all the IR radiation from the surface escapes immediately... escapes immediately...

– or the average temperature would be a or the average temperature would be a freezing –18freezing –18ºC ºC

– No liquid water or cloudsNo liquid water or clouds– And no life!And no life!

ClimateClimate science science Why do water vapour (HWhy do water vapour (H22O) and O) and

carbon dioxide (COcarbon dioxide (CO22) molecules ) molecules

‘trap’ heat radiation...‘trap’ heat radiation...

... when 99% of the atmosphere ... when 99% of the atmosphere (nitrogen and oxygen) just lets it (nitrogen and oxygen) just lets it all through?all through?

A little more physics!A little more physics! ‘‘Light’ can be ultraviolet (UV), visible, or Light’ can be ultraviolet (UV), visible, or

infrared (IR). It is measured by ‘wavelength’.infrared (IR). It is measured by ‘wavelength’.

R O Y G B VR O Y G B VIR UVIR UV

InfraredInfrared Ultraviolet Ultraviolet

1 µm 0.7 µm 0.4 µm 0.1 µm

1 µm = 1 thousandth of a millimetre

A little more physics!A little more physics! But light also comes as ‘photons’But light also comes as ‘photons’

Here’s a visible light one:Here’s a visible light one:

... but light never ‘stops’! ... but light never ‘stops’!

It either travels at ‘the speed of light’ or it is It either travels at ‘the speed of light’ or it is absorbed as energy.absorbed as energy.

A little more physics!A little more physics! Here’s an infrared one:Here’s an infrared one:

Notice that it has a longer wavelengthNotice that it has a longer wavelength

(And of course they don’t really look like this!)(And of course they don’t really look like this!)

Back to climateBack to climate science science How do those air molecules ‘trap’ the IR How do those air molecules ‘trap’ the IR

photons?photons?

Nitrogen (N2)Water vapour (H2O)

Oxygen (O2)

Carbon dioxide (CO2)

Of course molecules Of course molecules don’t ‘look’ like this either!don’t ‘look’ like this either!


NitrogenNitrogen and and oxygenoxygen molecules: molecules:

Two atoms ‘tightly bound’ Two atoms ‘tightly bound’

Some simple

Some simple^̂


WWaatteer and r and carboncarbon dioxidedioxide molecules: molecules:

Three atoms ‘loosely bound’Three atoms ‘loosely bound’

Some simple

Some simple^̂


NitrogenNitrogen and and oxygenoxygen molecules: molecules:

Light ‘photons’ (visible and IR) go right Light ‘photons’ (visible and IR) go right through through NN22 and and OO22

Some simple

Some simple^̂



Infrared photons get absorbed by HInfrared photons get absorbed by H22OO and and

CCOO22 molecules (and give them energy) molecules (and give them energy)

Some simple

Some simple^̂



The HThe H22OO and and CCOO22 don’t keep the energy...don’t keep the energy...

they ‘re-radiate’ it.they ‘re-radiate’ it.

Some simple

Some simple^̂

ClimateClimate science science Some of this re-radiated IR goes back down Some of this re-radiated IR goes back down

and warms the surface – a little like a and warms the surface – a little like a greenhouse...greenhouse...

The so called “Greenhouse Effect”The so called “Greenhouse Effect”

This keeps the Earth at a warm +15This keeps the Earth at a warm +15ooC C (average) instead of that freezing –18(average) instead of that freezing –18ooCC

More complex climateMore complex climate science science

ClimateClimate science science They reflect light back to spaceThey reflect light back to space (negative feedback)(negative feedback)

But also reflect IR back to the surfaceBut also reflect IR back to the surface (positive feedback)(positive feedback)


High clouds act differently to low cloudsHigh clouds act differently to low clouds

And there are aircraft contrails to be taken into account

ClimateClimate science science As well, there are:As well, there are: VolcanosVolcanos Vegetation changesVegetation changes AerosolsAerosols Heat exchange - ocean and air (ENSO)Heat exchange - ocean and air (ENSO) Ice and snow coming/goingIce and snow coming/going Glaciers changingGlaciers changing Changes in weather patternsChanges in weather patterns ... and lots more... and lots more ... including human added CO... including human added CO22!!

CO2 has probably not been this high for several CO2 has probably not been this high for several millionmillion yearsyears

NOW ~390


So what are we actually doing to the So what are we actually doing to the atmosphere and why does it matter?atmosphere and why does it matter?

(It’s not only carbon dioxide)(It’s not only carbon dioxide)

The basic data needed is measured in various ways and is well known. Notice that overall, incoming equals outgoing (342 = 107 + 235). Also, that large amounts of energy are absorbed and re-radiated by greenhouse gases.

(IPCC graph)

Let’s combine the incoming solar and reflected solar - leaves net of 235 incoming

342342-107-107=235=235

That’s equal to the total outgoing IR radiation.

Or was before we came along!

IPCC 2007

These are These are the the changes in changes in the forcing the forcing since pre-since pre-industrial industrial timestimes

This is the This is the problemproblem

The problem is that the added CO2 has increased the 324 back radiation by ~2 W/m2.

and therefore decreased the 235 outgoing by ~2 W/m2.

326326

233233

342342-107-107=235=235

The Earth is no longer in balance. Let’s make a simpler picture!

235235

235235233233

324324 326326 BackBackRadiationRadiation

350350

RadiationRadiationOth

erO

ther

Earth must warm in order to increase Earth must warm in order to increase outgoing 233 back to 235outgoing 233 back to 235

235235

233233235235

326326 330330 BackBackRadiationRadiation

350350 355355RadiationRadiationO

ther

Oth

er

This increases radiation AND Back This increases radiation AND Back Radiation until Radiation until totaltotal increases by 2 increases by 2

+1+1 +5

+4


Typical denier statement:Typical denier statement: “…“…the idiotic notion that the idiotic notion that

increasing by less than increasing by less than 1/2000 this century the 1/2000 this century the proportion of the Earth’s proportion of the Earth’s atmosphere occupied by atmosphere occupied by COCO22 may prove may prove

catastrophic.”catastrophic.” ““The Viscount Monckton of The Viscount Monckton of

Brenchley” in a letter to Kevin Brenchley” in a letter to Kevin Rudd 1 January 2010Rudd 1 January 2010


1/20001/2000thth ? ? Pre industrial COPre industrial CO22: 280 ppm =0.028% : 280 ppm =0.028%

≈ ≈ 3/10,0003/10,000 Now: 390 ppm = 0.039% Now: 390 ppm = 0.039% ≈ ≈ 4/10,000 So the increase so far has been ≈ 4/10,000 So the increase so far has been ≈

1/10,000 (well yes, it is less than 1/20001/10,000 (well yes, it is less than 1/2000thth!)!) These calculations are irrelevant!These calculations are irrelevant! 280 ppm 280 ppm 390 ppm is a 39% increase 390 ppm is a 39% increase 3/10,000 3/10,000 4/10,000 is a 33% increase 4/10,000 is a 33% increase


This can only be seen as a deliberate This can only be seen as a deliberate attempt to deceive by making the numbers attempt to deceive by making the numbers look small!look small!

Here is the effect of adding this ‘tiny Here is the effect of adding this ‘tiny proportion’ (300 ppm) of ink to a glass of proportion’ (300 ppm) of ink to a glass of water:water:


300 ppm (or 0.03%) might not sound like 300 ppm (or 0.03%) might not sound like much, but here is the effect of adding 300 much, but here is the effect of adding 300 ppm of ink to a glass of water:ppm of ink to a glass of water:


Remember that the greenhouse effect keeps Remember that the greenhouse effect keeps the Earth at +15°C instead of –18°C the Earth at +15°C instead of –18°C

We cannot expect that a 35% increase in COWe cannot expect that a 35% increase in CO22

a greenhouse gas won’t make a difference!a greenhouse gas won’t make a difference!

GHE

Note: Water vapour is the more important GHG, but the interaction between them is complex


Water vapour Water vapour and and carbon dioxidecarbon dioxide Deniers will claim that HDeniers will claim that H22O is responsible for about O is responsible for about

95% of the GHE95% of the GHE This is false – It is not a ‘linear problem’ This is false – It is not a ‘linear problem’ HH22O and COO and CO22 act differently act differently

Take away all H2O: Other GHGs absorb ~34%

Take away OGHGs: H2O absorbs ~85%

So effect of H2O ~ 66% – 85% [100 – 34 = 66]

So effect of OGHGs ~ 15% – 34% [100 – 85 = 15]

So CO2 on its own is 9% – 26% of the GHE [As

CO2 is about 60% of GHGs]


HH22O is a feedback GHG, O is a feedback GHG, COCO22 is a forcing GHG is a forcing GHG

– More COMore CO22 → → more warmth more warmth → more H→ more H22O O

(evaporation) → (evaporation) → more warmth more warmth → more H→ more H22O → O → more more

warmth warmth → → ??????– But also, more water vapourBut also, more water vapour → more clouds, → more clouds,

which...which...– reflect sunlight, and reflect sunlight, and reduce the warming effectreduce the warming effect..– and which ... and which ...

ClimateClimate science science reduce the amount of Hreduce the amount of H22O in the atmosphereO in the atmosphere

This is a This is a FeedbackFeedback effect effect Water vapour goes in and out of the atmosphere Water vapour goes in and out of the atmosphere

very quicklyvery quickly


Human added Human added HH22O is not a O is not a

problem – it problem – it soon rains out soon rains out again.again.


– But COBut CO22 is is

another story!another story!

ClimateClimate science science Carbon dioxide molecules remain in the Carbon dioxide molecules remain in the

air for ~ 100 yearsair for ~ 100 years Methane for about 20 yearsMethane for about 20 years There is There is NO FEEDBACKNO FEEDBACK effect that gets effect that gets

them out of the atmospherethem out of the atmosphere That makes a very big difference in the That makes a very big difference in the

way they act.way they act. COCO22 and CH and CH44 (methane) are called (methane) are called

FORCINGFORCING greenhouse gases greenhouse gases

ClimateClimate science science There is another important difference There is another important difference

between the three main greenhouse between the three main greenhouse gases.gases.

They absorb They absorb different parts different parts of the IR of the IR spectrum...spectrum...


HH22OO and and CCOO22 molecules can take on the molecules can take on the

energy in many different ways:energy in many different ways:

More simpleMore simple

^̂


Which means they absorb various different Which means they absorb various different types of infrared photons.types of infrared photons.

(Light photons vary in their ‘wavelength’)(Light photons vary in their ‘wavelength’) Shorter wavelengthShorter wavelength

Longer wavelength infraredLonger wavelength infrared

More simpleMore simple

^̂


This means that they absorb different parts This means that they absorb different parts of the IR radiation from the Earth’s surface.of the IR radiation from the Earth’s surface.

Absorbed Absorbed mostlymostlyby COby CO22

Short wavelength Long wavelength0.1 µm (µm = millionth of a metre) 100 µm


H2O CO2

CH4

Absorption spectra for greenhouse gases


That means that even if the atmosphere is That means that even if the atmosphere is saturated with water vapour a lot of IR still saturated with water vapour a lot of IR still gets through.gets through.

COCO22 and CH and CH44 absorb IR wavelengths that absorb IR wavelengths that

HH22O doesn’t.O doesn’t.

(Many “sceptics” don’t seem to understand (Many “sceptics” don’t seem to understand that!)that!)

ClimateClimate science science The BIG QUESTIONS:The BIG QUESTIONS:

– If we continue to increase the greenhouse gases how If we continue to increase the greenhouse gases how much will the temperature increase?much will the temperature increase?

– Will that matter?Will that matter?

ClimateClimate science science The BIG QUESTIONS:The BIG QUESTIONS:

– If we continue to increase the greenhouse gases how If we continue to increase the greenhouse gases how much will the temperature increase?much will the temperature increase?

– Will that matter?Will that matter?

How can we find out?How can we find out?– We need to use our understanding of the We need to use our understanding of the

science of climate change.science of climate change.– This is done mostly by putting the data into This is done mostly by putting the data into

computer models and using the laws of physics.computer models and using the laws of physics.


To take all this into account scientists put all To take all this into account scientists put all the laws of physics and chemistry into the laws of physics and chemistry into computer models which can do the vast computer models which can do the vast numbers of calculations needed.numbers of calculations needed.

Some of the equations:Some of the equations:

ClimateClimate science science The models divide the atmosphere and The models divide the atmosphere and

ocean into cells about 1 km deepocean into cells about 1 km deep

ClimateClimate science science The cells have been The cells have been

getting smaller with getting smaller with better computers.better computers.

Initial conditions are Initial conditions are put in and then...put in and then...

mass (wind) and mass (wind) and energy (heat) transfer energy (heat) transfer between cells is between cells is calculated...calculated...

and recalculated and recalculated billions of times!billions of times!

1995

2001

2007

ClimateClimate science science The models produce results rather like a The models produce results rather like a

weather map, but over decades or centuriesweather map, but over decades or centuries

ClimateClimate science science The models are checked by putting in data The models are checked by putting in data

from long ago and ‘back forecasting’from long ago and ‘back forecasting’

ClimateClimate science science Here are the results of a 150 year run:Here are the results of a 150 year run:

Global average temperature increase

ClimateClimate science science But that was But that was without human added COwithout human added CO22::


ClimateClimate science science Here is the result Here is the result with human added COwith human added CO22::


ClimateClimate science science The models correctly predict volcanic effects The models correctly predict volcanic effects

1963 Agung1982 El Chichon1991 Pinatubo



This is why scientists This is why scientists believe that human believe that human added COadded CO22 is is

a problem!a problem!

It is not just rising temperatures, melting ice, It is not just rising temperatures, melting ice, more extremes etc.more extremes etc.


Computer models are often criticised on the Computer models are often criticised on the basis of the bad performance of economic basis of the bad performance of economic models (the GFC!)models (the GFC!)

Economic models: Economic models: Human guesses about human behaviour !!!Human guesses about human behaviour !!! Climate models: Climate models: The laws of physics and chemistry and The laws of physics and chemistry and

detailed observations.detailed observations.


We can also look at the past climate to We can also look at the past climate to find clues about what can happen.find clues about what can happen.

These temperatures are more approximate the further back in time we go.

“Climate change is natural” ... Yes but!

ClimateClimate science science So is sea level change:So is sea level change:

during the during the last interglacial period last interglacial period when sea level peaked at around when sea level peaked at around 6 metres higher than today6 metres higher than today. His findings suggest that at one point . His findings suggest that at one point the sea rose the sea rose 3 metres within 50 to 100 years3 metres within 50 to 100 years.”.”

““Paul Blanchon's Paul Blanchon's team at the National team at the National Autonomous Autonomous University of Mexico University of Mexico in Cancun has been in Cancun has been studying 121,000 studying 121,000 year old coral reefs year old coral reefs in the Yucatan in the Yucatan Peninsula, formedPeninsula, formed

Temperatures in that interglacial were only a couple of degrees warmer than the 20Temperatures in that interglacial were only a couple of degrees warmer than the 20 thth C. C.


Is it really CO2 though?Is it really CO2 though? The physics says it is.The physics says it is. Geological history says it is...Geological history says it is...

TodayToday 390390


Is it really CO2 though?Is it really CO2 though? and the recent data says it is...and the recent data says it is...


Certainly the temperature is dependent on Certainly the temperature is dependent on many other factors AS WELL...many other factors AS WELL...

... (why don’t deniers understand that?)... (why don’t deniers understand that?) The sun cycles...The sun cycles...


Certainly the temperature is dependent on Certainly the temperature is dependent on many other factors AS WELL...many other factors AS WELL...

And the ENSO (El Niño Southern Oscillation)And the ENSO (El Niño Southern Oscillation)

Very Large Very Large El Niño El Niño 19981998

La NiñasLa Niñas

Also note the drops Also note the drops following volcanoesfollowing volcanoes

The annual variation is about The annual variation is about ten times the warming trendten times the warming trend

We We seesee the weather more the weather more than the warming!than the warming!


The effects of climate change are not The effects of climate change are not uniform warming.uniform warming.

Some areas will warm faster and some very Some areas will warm faster and some very slowly.slowly.

Some will get wetter, some dryerSome will get wetter, some dryer

Average temperature increases for 2000 – Average temperature increases for 2000 – 2009 compared to 1951 - 19802009 compared to 1951 - 1980

Monthly average temperature increases forMonthly average temperature increases for December 2009December 2009 compared to 1951 – 1980 compared to 1951 – 1980 Average global +0.62°CAverage global +0.62°C

Climate Science Keith Burrows Science Teachers for Climate Awareness This presentation is designed...

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