Ozone, Air Pollution, and Ozone, Air Pollution, and Earth’s Energy BalanceEarth’s Energy Balance

Presented by Presented by Stephen SchneiderStephen SchneiderDeborah CarlisleDeborah Carlisle

June, 2012June, 2012

Human Energy ConsumptionHuman Energy Consumption Humans worldwide use ~4 ×10Humans worldwide use ~4 ×102020 Joules Joules

of energy per year. (U.S. 25% of this.)of energy per year. (U.S. 25% of this.) In just 1 second the Sun generates In just 1 second the Sun generates

enough energy to supply humans for:enough energy to supply humans for: time = 4 × 10time = 4 × 102626 Joules/4 ×10 Joules/4 ×102020 Joules/year Joules/year

= 10= 106 6 yearsyears

The amount of sunlight striking the Earth The amount of sunlight striking the Earth is ~ 5 ×10is ~ 5 ×102424 Joules per year. We use Joules per year. We use 1/10,0001/10,000thth as much. as much.

Energy FlowEnergy FlowTo solve a crime, “follow the money.” To To solve a crime, “follow the money.” To

understand the global balance of the understand the global balance of the Earth, “follow the energy.”Earth, “follow the energy.”

Energy changes form but the total amount Energy changes form but the total amount is always conserved. is always conserved.

Energy eventually “degrades” into heat.Energy eventually “degrades” into heat. A place reaches a higher temperature A place reaches a higher temperature

when energy spends more time there—but when energy spends more time there—but just as much energy is always emitted as just as much energy is always emitted as is absorbed. (ex: the Sun’s core generates is absorbed. (ex: the Sun’s core generates as much energy as the Sun radiates.)as much energy as the Sun radiates.)

Energy Energy BalanceBalance

To be stable, just To be stable, just as much energy as much energy must come in as must come in as goes out.goes out.

Subsystems Subsystems (ground, air) also (ground, air) also remain balancedremain balanced

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A

BD

E

C

F

Energy Balance DiagramEnergy Balance Diagram

The Ozone The Ozone ProblemProblem

What happens What happens when we when we change the change the ability of the ability of the atmosphere to atmosphere to absorb the absorb the Sun’s radiation?Sun’s radiation?

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Ozone (parts per million)

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Ozone In the AtmosphereOzone In the AtmosphereA

ltitude (miles)

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90% of ozone is in the stratosphere

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10% of ozone is in the troposphere

UVc - 100% AbsorptionUVb - 90% Absorption

UVa - 50% Absorption & Scattering

Ozone (parts per million)

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The Ozone Layer Absorbs The Ozone Layer Absorbs Ultraviolet EnergyUltraviolet Energy

The stratosphere is almost as warm as the surface!

Nuclear Nuclear WinterWinter

What happens What happens when we add when we add dust to the dust to the atmosphere, so atmosphere, so it becomes it becomes more reflective?more reflective?

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Global Dust StormsGlobal Dust Storms

• Huge dust storms can cover all of Mars, rapidly cooling the planet.

• This helped to develop the idea of “nuclear winter,” after a nuclear war or asteroid impact

Global Global WarmingWarming

What happens What happens when we make when we make the atmosphere the atmosphere absorb more absorb more infrared infrared radiation from radiation from the surface?the surface?

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Global Warming and IR LightGlobal Warming and IR Light

Carbon dioxide and water absorb infrared Carbon dioxide and water absorb infrared radiation, mostly reradiated from the surface, radiation, mostly reradiated from the surface, trapping it and warming the surface.trapping it and warming the surface.

The Surface of VenusThe Surface of Venus

Several Russian Venera spacecraft landed on the surface Several Russian Venera spacecraft landed on the surface of Venusof Venus

Surface temperature measured to be ~750K!Surface temperature measured to be ~750K! Surface pressure about 90 atmospheres—like being 3000 Surface pressure about 90 atmospheres—like being 3000

feet underwater!feet underwater! Earth has a comparable amount of carbon dioxide locked Earth has a comparable amount of carbon dioxide locked

up in rocks and the oceans.up in rocks and the oceans.

If Earth’s Oceans Got Too WarmIf Earth’s Oceans Got Too Warm Evaporating oceans add greenhouse gases, Evaporating oceans add greenhouse gases,

causing more heating, so more evaporation… causing more heating, so more evaporation…

Recent data from the Venus Express mission Recent data from the Venus Express mission indicates rocks probably formed in water.indicates rocks probably formed in water.

Changes in Changes in InsolationInsolation

What happens What happens when the when the amount of light amount of light from the Sun from the Sun changes?changes?

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SunspotsSunspots Cooler regions in Cooler regions in

Sun’s photosphere—Sun’s photosphere—still bright, but look still bright, but look dark by contrast!dark by contrast!

Huge plasma storms Huge plasma storms on Sun’s surface.on Sun’s surface.

Regions of intense Regions of intense magnetic fields.magnetic fields.

Sun’s overall energy Sun’s overall energy output increases.output increases.

Solar Solar WindWind

When Sun is more active, the outflow

of particles is stronger, and we

see aurora borealis.

The Solar CycleThe Solar Cycle

The number of sunspots goes up and down The number of sunspots goes up and down about once every 11 years on average.about once every 11 years on average.

After each sunspot maximum, the Sun’s After each sunspot maximum, the Sun’s magnetic field reverses.magnetic field reverses.

We are currently in an unusual lull in We are currently in an unusual lull in sunspot activity.sunspot activity.

Long Term Changes in the SunLong Term Changes in the Sun

You might expect that the Sun is darker You might expect that the Sun is darker when it has more sunspots, but when it is when it has more sunspots, but when it is more active it generates more power overall.more active it generates more power overall.

This appears to affect Earth’s climate.This appears to affect Earth’s climate. In the 1600s there was a period with very few In the 1600s there was a period with very few

sunspots—and a “little ice age” on Earth.sunspots—and a “little ice age” on Earth.

Longer Term Changes in the SunLonger Term Changes in the Sun

Occasional records suggest longer term changes in Occasional records suggest longer term changes in the Sun’s energy output.the Sun’s energy output.

Can also look at trace isotopes carried to Earth by Can also look at trace isotopes carried to Earth by the Solar Wind.the Solar Wind.

In medieval times the Sun was more luminous and In medieval times the Sun was more luminous and Greenland was green!Greenland was green!

The Sun’s Life HistoryThe Sun’s Life History

Very Long Term Changes of the SunVery Long Term Changes of the Sun

• The Sun is about mid-way through its main hydrogen fusion phase, and will last another 5-6 billion years.

• Studies of other stars and computer models indicate stars grow steadily more luminous in this phase

• The Sun was only ~½ as luminous when it was born, and will be ~2 times more luminous in 5 billion years.

• In “just” 100 million years, it should be so luminous that Earth will undergo runaway greenhouse (like Venus)

• Earth is relatively cool now thanks to bacteria that have removed CO2 from our atmosphere.

Earth Today: The Ice AgesEarth Today: The Ice Ages We live in an We live in an

“icehouse” period “icehouse” period that has been that has been around for the last around for the last ~1 million years.~1 million years.

Typified by short Typified by short warm interglacials warm interglacials and then long and then long declines into declines into glacial episodes. glacial episodes.

Earth’s Changing Orbit Earth’s Changing Orbit Earth’s axis precesses Earth’s axis precesses

Period = 26,000 yrPeriod = 26,000 yr

Earth’s axis becomes Earth’s axis becomes more or less tilted more or less tilted Period = 40,000 yrPeriod = 40,000 yr

Earth’s orbit becomes Earth’s orbit becomes more or less elliptical more or less elliptical Period = 100,000 yrPeriod = 100,000 yr

There seems to be a link between these orbital changes and the regular cycle of hot and cool periods

Milankovitch CyclesMilankovitch Cycles

Sedimentary layers in Welsh coast show variations every ~100,000 yr (from about 300 million years ago)