PowerPoint Presentation

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Structure of the AtmosphereThermosphereMesosphereOzone Maximum

Stratosphere

TroposphereTemperature

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Have you seen a greenhouse?Most greenhouses look like small glasshouses.

Green houses are used to grow plants, especially in the winter.

What is the Greenhouse effect?The greenhouse effect is the rise in temperature that the Earth experiences because certain gases in the atmosphere trap heat from the Suns rays.

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How do greenhouses work?This causes the greenhouse to heat up much like the inside of a car parked in sunlight, and keeps the plants warm enough to live in the winter.

The Greenhouse EffectSunshine enters the Earths atmosphere passing through the blanket of greenhouse gases.As it reaches the Earths surface, land, water, and biosphere absorb the sunlights energy! Once absorbed this energy is sent back into the atmosphere.7

How do greenhouses work?Greenhouses work by trapping heat from the sun.

The glass panels of the greenhouse let in light but keep heat from escaping.

Greenhouse EffectWithout these gases, heat would escape back into space and Earths average temperature would be about 60 F colder.

Because of how they warm our world, these gases are referred to as greenhouse gases.

Atmospheric influences on radiationReflectionScattering

Absorption (absorber warms)12

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Earths energy budget (averaged over the whole globe and over a long time)At the top of the atmosphere: Incoming shortwave = Reflected Shortwave+ Emitted longwaveAt the surface: Incoming shortwave = Reflected shortwave + Net emitted longwave (emitted - incoming) + Latent heat flux + sensible heat flux

Sensible heat 7%Latent heat 23%Net Longwave 21%Yellow: shortwaveRed: longwave13

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The greenhouse effect is important.Without the greenhouse effect, the Earth would not be warm enough for humans to live.

But if the greenhouse effect becomes stronger, it could make the Earth warmer than usual.

Even a little warming causes problems for plants and animals.

What controls climate?Energy from the Sun RadiationConsider the 4 inner planets of the solar system:SUNReceives342 W m-2 solar radiation1RelativeDistance from Sun

0.390.721.52250 W m-2660 W m-2150 W m-2Scales with 1distance2

Mercury

Venus

Mars

Earth

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Planetary AlbedoA fraction of the incoming solar radiation (S) is reflected back into space, the rest is absorbed by the planet. Each planet has a different reflectivity, or albedo ():Earth = 0.31 (31% reflected, 69% absorbed)Mars = 0.15Venus = 0.59Mercury = 0.1One possible way of changing Earths climate is by changing its albedo.17

Land has higher albedo than ocean

Clouds have high albedo

Ice and snow have high albedo18

Radiative EquilibriumEach planet must balance net incoming solar radiation with outgoing radiation, determined by its temperature.Stefan-Boltzmann Law:A body at temperature T radiates energy at a rate proportional to T4 (T in Kelvin)Balance incoming and outgoing radiation: Net incoming radiation=Outgoing radiationS(1-)= T4( is the Stefan-Boltzmann constant = 5.67 x 10-8 W m-2 K-4)

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Temperature of the inner planetsRelative distanceSolar radiation (S) W m-2Albedo()Net solar radiationS(1- )Equilib-rium T (C)Actual surface T (C)Mercury0.3922500.1180Venus0.726600.59453Earth13420.31236-1915Mars1.51500.15-43

S(1-) = T4( = 5.67 x 10-8 W m-2 K-4)Rearranging: T = S(1- )

{} T(C) = T(K) - 273

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Temperature of the inner planetsRelative distanceSolar radiation (S) W m-2Albedo()Net solar radiationS(1- )Equilib-rium T (C)Actual surface T (C)Mercury0.3922500.12025162180Venus0.726600.59271-10453Earth13420.31236-1915Mars1.51500.15128-55-43

S(1-) = T4Rearranging: T = S(1- )

{} T(C) = T(K) - 273( = 5.67 x 10-8 W m-2 K-4)

Just about agreesDisagrees badlyDisagreesNearly agrees21

3 Types of Scattering: RaleighMieNon-Selective

Atmospheric ScatteringA discussion of each type follows22

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involves gases smaller than insolation wavelengthscatters light in all directions most effective at short wavelengths (violet, blue) hence, blue skyRayleigh Scattering

The Earth has an atmosphere. So it has Rayleigh scattering and its sky appears blueThe Moon has no atmosphere. So it has no Rayleigh scattering and its sky appears dark23

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Rayleigh scattering also explains reddish-orange sunsets when light travels through thick slice of atmosphere

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2) Mie scatteringinvolves aerosols (e.g. dust, smoke) larger than gas moleculesforward scatterequally effective across visible spectrumexplains hazy, gray days

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3) Non-selective scatteringHappens when atmospheric particles are much larger than the wavelength of incoming radiation (e.g. water droplets in clouds)Act like lenses; scatter all wavelengths equally to create a white appearanceThats why clouds appear white

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What are these gases?The greenhouse gases are:

Water VapourCarbon dioxideNitrous OxideMethaneCFCs

Water VapourWater vapour is the biggest contributor to the natural greenhouse effectHuman activities have little impact on the level of water vapour.

Carbon DioxideOur atmosphere contains many natural gases other than ozone. One of these natural gases is carbon dioxide.

Our atmosphere needs a certain amount of this gas. It is carbon dioxide that helps to keep the Earth warm.

Carbon DioxideCarbon Dioxide is probably the most important of the greenhouse gases and is currently responsible for 60 % of the enhanced greenhouse effectEnhancedHuman activities, not natural.

Global carbon dioxide emissions

Global CO2 emission

Nitrous OxideNitrous oxide makes up an extremely small amount of the atmosphere It is less than one-thousandth as abundant as carbon dioxide.

However it is 200 to 300 times more effective in trapping heat than carbon dioxide.32

Nitrous OxideThe impact of human activities

Burning fossil fuels and woodWidespread use of fertilizersSewage treatment plants

Methane The importance of methane in the greenhouse effect is its warming effect.

It occurs in lower concentrations than carbon dioxide but it produces 21 times as much warming as carbon dioxide.

MethaneHuman ActivitiesAn increase in livestock farming and rice growing has led to an increase in atmospheric methane. Other sources are the extraction of fossil fuels, landfill sites and the burning of biomass. Methane concentration in the atmosphere has more than doubled during the last 200 yr. Some of this methane is produced by ricefields

Where do all the methane gases come from?

MethaneProduced by bacteria living in swampy areas.Wet rice cultivationWaste in landfills Rearing of livestockWhen cows belch (burp)Each molecule can trap 20 times as much heat as a CO2 molecule.

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Where do all the CFCs come from?

CFCs (Chlorofluorocarbons)Aerosol spraysCoolants in fridge and air consCleaning solventsEach CFC molecule can trap as much heat as 100 000 CO2 molecule.Can remain in the atmosphere for a long time (up to 20 000 years)

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Global Warming ImpactsThe average global temperature has increased by almost 1 F over the past century.

Scientists expect the average global temperature to increase an additional 2 to 6 F over the next hundred years.

Sea Level RiseGlobal Warming may make the sea level become higher. Why?Warmer weather makes glaciers melt.Melting glaciers add more water to the ocean.Warmer weather also makes water expand.When water expands in the ocean, it takes up more space and the level of the sea rises.40

Rising Sea Levels

When earths temperature rises, sea level is likely to rise too:Higher temperature sea water to expand in volumeIce caps at poles to melt

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Sea Level RiseSea level may rise between several inches and as much as 3 feet during the next century.Coastal flooding could cause saltwater to flow into areas where salt is harmful, threatening plants and animals in those areas.Oceanfront property would be affected by flooding.Coastal flooding may also reduce the quality of drinking water in coastal areas.42

Climatic Change

Global warming will lead to an increase in the evaporation of water more water vapour.With more water vapour, more rain fall is expected.But it is not evenly distributed:Dry areas severe drought condition, water shortage and heat waves occursWet areas floods and avalanches (landslides)

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Climatic Change

Other problems may arise:Destroy food crop rice, wheat and cornAffect animals need to migrateEncourage growth of weed and pests may lead to diseases like dengue fever, cholera which are deadly.

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Summary / ConclusionEnvironmental Crisis will affect us:HealthAir pollution asthma or other respiratory problemsWater pollution poison our food source e.g fishDestruction of forest lost of possible medical solutionsPropertyFloods property lostPollution destroy streets and beachesSoil erosion desertification, lost of farm lands

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Water on Mars Today? The gullies form when snow accumulates on the crater walls in winter and melts away in spring. Because the gullies are relatively small (note the scale bar in Figure 7.26), they should be gradually covered over by blowing sand during Martian dust storms. Thus, gullies that are still clearly visible must be no more than a few million years old. Geologically speaking, this time is short enough to make it quite likely that water flows are still forming gullies today

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