Protons for Breakfast Week 4: Global Warming

In the event of an alarm sounding…

Global Warming Can we collect your facts please…

What do we mean by Climate? What is the Climate? It’s the average weather in a particular area What is the Climate? It’s the average weather Over a period a time (30 years usually) Averages of temperatures and rain occurrence Calculated scientifically Things like that determine what we call the Climate Determine what the climate of a place will be.

One problem… Do you have any personal evidence that the global climate is changing?

This Evening… 1.Why is the Earth’s surface the temperature it is? 2.The Earth’s Atmosphere 3.Increasing Carbon Dioxide 4.Should we be concerned? 5.What’s going to happen? 6.What should we do?

Energy Balance

How hot does an object get when placed in front of a fire?

Light from the Sun heats the Earth… The Sun Earth 5400 °C

Light from the Sun heats the Earth… Drawn to Scale… The Sun Earth (drawn 100 times too big) (drawn to scale)

Light from the Sun heats the Earth… The Earth then radiates heat away… Light from the Sun Earth

Energy Balance heat input from the Sun heat lost from the Earth by radiation When there is balance, the Earth’s average temperature will be stable Earth Warms Earth Cools

The Energy Balance of the Earth

Earth Warms Earth Cools Energy Balance: to scale World Energy Production heat input from the Sun heat lost from the Earth

Some more details…

How much light reaches the Earth? Earth At the top of the atmosphere Above the Equator At midday About 1360 W/m 2

How much light reaches the Earth? Earth North Pole South Pole Equator 1360 W/m Whole Earth Average 340 W/m 2

How much light reaches the Earth’s Surface Light reflected from Earth Average Value 100 watts per square metre Light from the Sun Average Value 340 watts per square metre

Hold on a moment! What about all the heat rising up from the Earth’s hot centre?

Earth 6400 km radius 5500 °C Heat flow is less than 0.1 Watt per square metre Temperature increases by ~20 °C for each kilometre below the Earth’s surface Heat flow to and from surface from the Sun 240 Watt per Square metre

A remarkable fact… Heat flow from the centre of the Earth can be completely ignored when considering what determines the surface temperature of the Earth!

What determines the surface temperature of the Earth? Infra Red Radiation cools the Earth… Light from the Sun heats the Earth…

Radiation Balance Light from the Sun heats the Earth… Average Value 240 watts per square metre Average Value 240 watts per square metre

Radiation Balance How hot must the Earth be to radiate 240 W/m 2 ? Average Value 240 watts per square metre -18 °C

A Question What is the average temperature of the Earth? 1 metre above the surface and averaged over: day and night, all latitudes and longitudes. all seasons (a) – 15 ° C (b) – 5 ° C (c) + 5 ° C (d) + 15 °C

Summary -18 °C Average Surface Temperature 33 °C Temperature for radiation balance +15 °C Greenhouse Effect

The Earth’s surface is 33 °C warmer than it would be if had no atmosphere

This Evening… 1.Why is the Earth’s surface the temperature it is? 2.The Earth’s Atmosphere 3.Increasing Carbon Dioxide 4.Should we be concerned? 5.What’s going to happen? 6.What should we do?

The composition of the atmosphere? Gas% Nitrogen (N 2 )78.1 Oxygen (O 2 )20.1 Argon (Ar)0.93 Water (H 2 O)0.1 to 1 Carbon Dioxide (CO 2 )0.035

Illustration of atmospheric composition About 100 molecules O2O2 Ar N2N2

Illustration of atmospheric composition About 1200 molecules Water(H 2 O)

Illustration of atmospheric composition About molecules Carbon dioxide (CO 2 )

Nitrogen (N 2 ), Oxygen (O 2 ) & Argon (Ar) Suppose the atmosphere contained no carbon dioxide or water N 2, O 2 and Ar is more than 99% of the atmosphere Molecules have one or two atoms Natural frequency of vibration in the ultra-violet Make atmosphere opaque to ultra-violet light Transparent to infra-red and visible radiation

Nitrogen (N 2 ), Oxygen (O 2 ) & Argon (Ar) With an atmosphere of only Nitrogen Oxygen & Argon, what would be the surface temperature? Average Value 240 watts per square metre Average Value 240 watts per square metre -18 °C

Greenhouse warming is caused by Water (H 2 O) Carbon Dioxide (CO 2 )

What is special about H 2 O and CO 2 Molecules have three atoms Natural frequencies of vibration in the infra-red They make the atmosphere opaque to certain infra- red frequencies

Vibrations of CO 2 and H 2 0 Different types of molecular jiggling occur at different frequencies Water H 2 0 Carbon dioxide C0 2

Absorption demo Frequency

The Transparency of the Atmosphere

Warning! Complicated diagram !

Infra RedUltra VioletVisible Absorption bands SUN 6400 °C (left-hand scale)

Infra Red Radiation cools the Earth…

Radiation Balance in the 20 th Century… On Average 240 W/m 2 On Average 390 W/m W/m 2 sent back to Earth Average Value 240 W/m 2 On Average + 15 ºC

Greenhouse Warming 33 °C Others <1 °C CO 2 2 °C H 2 O 31 °C If H 2 O is a more important greenhouse gas than CO 2, why aren’t we worried about water vapour emissions?

Residence time Because excess H 2 O in the atmosphere causes rain within a few days Excess CO 2 in the atmosphere takes a few hundred years to remove Photo Credit If H 2 O is a more important greenhouse gas than CO 2, why aren’t we worried about water vapour emissions?

How the parts fit together Atmospheric Water Global Temperature Greenhouse Effect Evaporation Small slowly changing contribution to Greenhouse Effect Clouds Carbon Dioxide

Experiment Does water block infrared light?

A Children’s song What does the glass of a Greenhouse do? It lets the short solar rays pass through The objects in the house absorb these rays And re-radiate them as long heat waves What does the glass of a Greenhouse do? It doesn’t let the long heat rays pass through Trapped by the glass they bounce back and forth, Re-radiate and reabsorbed Stay Stay, you long heat rays Warm up the house on coooold cold days The atmosphere is like a greenhouse too? It lets most of the solar rays through The surface of the Earth absorbs these rays And re-radiates them as long heat waves There’s vapour in the air, What does it do? It doesn’t let the long heat rays pass through Trapped by the vapour they bounce back and forth, Re-radiate and reabsorbed Stay Stay, you long heat rays Warm up the Earth on cooooold cold days

Greenhouse Effect Earth’s surface is warmed by the Greenhouse Effect Caused by: Water (mainly) and carbon dioxide Turns the Earth from a ‘snowball’ with a hot Equator into the relatively temperate place So what’s the problem?

This Evening… 1.Why is the Earth’s surface the temperature it is? 2.The Earth’s Atmosphere 3.Increasing Carbon Dioxide 4.Should we be concerned? 5.What’s going to happen? 6.What should we do?

Atmospheric CO 2 Concentration versus year Historical Value 280 ppm Current value ~390 ppm parts per million Click for latest value

Carbon dioxide Why is the amount of carbon dioxide in the Earth’s atmosphere is increasing? We are digging up carbon as: Coal & Oil & Gas We are burning them! C+ O 2 →CO 2

Michael’s family CO 2 emissions 0.2 kg per mile 4000 miles per year 800 kg CO 2 /year 0.3 kg per mile per person 1000 miles per year 600 kg CO 2 /year 0.5 kg per kWh 7300 kWh per year 3650 kg CO 2 /year Holiday in California! person miles! 8,000 kg CO 2 /year 0.2 kg per kWh kWh per year 3400 kg CO 2 /year

My family’s CO 2 emissions 8500 kg of CO 2 per year at home 8000 kg For our holiday in California! 16.5 tonnes!! There are many families like Michael’s…

Carbon? Or Carbon dioxide? CO2O2 1 tonne of CO tonne of C 0.73 tonne of O 2

Global CO 2 Emissions 30 billion tonnes CO 2 8 billion tonnes C EVERY YEAR

Question Is 8 billion tonnes of carbon per year (emitted as CO 2 ) a lot or a little?

Carbon Cycle (Amounts of carbon in billions of tons) ,000 39, ,000 3,000 (Coal) 300 (Oil &Gas) increasing at 4 per year 60

Cause for Concern? What is the effect of increased levels of carbon dioxide in the Earth’s atmosphere? Nobody knows

Radiation ‘Balance’ in 2012… On Average <240 W/m 2 On Average 390 W/m W/m 2 sent back to Earth Average Value 240 W/m 2 On Average + 15 ºC +2 W/m 2 +?? ºC

Earth Warms Earth Cools Energy Balance: to scale heat input from the Sun heat lost from the Earth

An Analogy

This Evening… 1.Why is the Earth’s surface the temperature it is? 2.The Earth’s Atmosphere 3.Increasing Carbon Dioxide 4.Should we be concerned? 5.What’s going to happen? 6.What should we do?

4. Why are scientists are concerned 1.Pre-historic studies show a strong correlation between atmospheric CO 2 levels and global climate. 2.There are observed changes in climate

Cause for Concern? Prehistoric Studies 1 year of snow From approximately 16,250 years ago

Bubbles in Arctic and Antarctic Ice 300 ppm Maximum180 ppm Minimum Ice Ages 390 ppm

Cause for Concern? Observed Changes in Climate

A Question? What has happened ? What did Global Warming Theory predict in 1981? But its not just average temperature that matters

Glaciers Muir Glacier, Alaska Photo credit: Global Warming Art Glaciers are retreating: worldwide

A Question Can we be completely sure that the climate changes we observe are caused by anthropogenic emissions of carbon dioxide? Man-made and Woman-made 2001: It is likely 2007: It is very likely

Climate Models ‘What’s going to happen?” Climate Models ‘add up’ the many factors Nobody knows

The best ‘realistic’ possibility… If we make a 50% cut in global emissions: 80% cut in the UK CO 2 concentraions will rise to twice historical levels and stabilise

IPCC Predictions… Global Mean Temperature We stop all emissions NOW We BEGIN to stop all emissions EVENTUALLY We BEGIN to stop all emissions NOW We do nothing

This Evening… 1.Why is the Earth’s surface the temperature it is? 2.The Earth’s Atmosphere 3.Increasing Carbon Dioxide 4.Should we be concerned? 5.What’s going to happen? 6.What should we do?

What should we do… NothingEverythingSomething

What could we do? What should we do? In smaller groups Please come up with some questions, and suggestions We will gather these together and then discuss them! You decide!

Despair? You may never know what results come of your action, but if you do nothing, there will be no result. Mahatma Ghandi

See you next week to discuss… Mobile Phone Safety! Goodnight

Unused Slides.

Contributions to Climate Forcing Greenhouse gases Carbon Dioxide Methane Chlorofluorocarbons Nitrous Oxide Ozone Aerosols Black Carbon Reflective aerosols Cloud droplet changes Land cover changes Sun Climate Forcing (W/m 2 ) 0+1

Feedback Global Temperature More Evaporation Climate Forcing Increased Climate Forcing Increased Water Vapour Increased Cloud Cover Decreased Climate Forcing Negative Positive

Powers of Ten (Global Warming) Length scale in metres Very Very Small Very Very Large Human Relationships Diameter of the Earth Distance to the Sun Tallest Mountain Deepest Trench Atoms & Molecules Microbes The phenomenon of global warming involves physical processes with length scales spanning 20 powers of 10!

The spectrum of sunlight

Global CO 2 Emissions ?

IPCC Predictions… Climate Research Unit East Anglia University metres in 100 years ? 1 metre

IPCC Predictions… 1 metre in 100 years

UK CO 2 Emissions

Daily Rotation Northern Hemisphere Summer Northern Hemisphere Spring Equinox Northern Hemisphere Winter Northern Hemisphere Autumn Equinox Angle varies from 22.5º to 24.5º And back again every 40,000 years 23.5º tilt Earth Spins times on its journey around the Sun

Carbon dioxide The amount of carbon dioxide in the Earth’s atmosphere is increasing… Historically280 ppm ppm ppm 2025about 425 ppm ppm

Cause for Concern? Climate models

Climate Models What is a computer model of the climate? © Australian Bureau of Meteorology

Climate Models What is the output of a climate model?

Atmospheric CO 2 Concentration versus year (Detail 2) Click Graph to link to NOAA Web Site for Latest Data

The Earth Orbits the Sun Daily Rotation Northern Hemisphere Summer Northern Hemisphere Winter Angle varies from 22.5º to 24.5º And back again every 40,000 years 23.5º tilt Earth Spins times on its journey around the Sun

Most Southerly Advance Mid Winter Seasonal Changes in Ice Cover

Most Southerly Advance Mid Winter Most Northerly Retreat Mid Summer If summer day length increases by a minute or two or days are warmer on average by a small amount This area used to reflect 90% of sunlight Now it reflects only around 30% Warmer ground emits trapped CO 2 and Methane

Is 380 Parts per million a lot or a little? Camera Light 380 ppm ‘blue’

Pre-Historic studies Bubbles in Arctic and Antarctic Ice Range of variation in last 800,000 years Current value 390 ppm

An additional 2 watts per square metre of ‘radiative forcing’ Scientific American March 2004

Observed Changes Average surface temperature is difficult to measure

Observed changes It is difficult to detect small changes in a long series of data?

Infra RedUltra VioletVisible Water Absorption bands SUN 6400 °C (left-hand scale) HEATER 1000 °C

IPCC Predictions… Annual CO 2 Emissions (GT C) Atmospheric CO 2 (ppm) A1F A1T A1F A1T

IPCC Predictions… Global Mean Temperature We stop all emissions NOW We BEGIN to stop all emissions EVENTUALLY We BEGIN to stop all emissions NOW We do nothing