Atmosphere and ClimateAtmosphere and Climate

Chapter 7Chapter 7

THE ATMOSPHERETHE ATMOSPHERE

The AtmosphereThe Atmosphere

Many nearby planets, like Mars and Venus, Many nearby planets, like Mars and Venus, are barren and lifeless.are barren and lifeless.

What allows life on Earth?What allows life on Earth?

The earth has an atmosphere.The earth has an atmosphere. The atmosphere is a thin layer of gases that The atmosphere is a thin layer of gases that

surrounds the Earth.surrounds the Earth. It extends from the surface of the earth to It extends from the surface of the earth to

hundreds of kilometers above the surface.hundreds of kilometers above the surface.

The AtmosphereThe Atmosphere

The atmosphere is 78% Nitrogen and 21% The atmosphere is 78% Nitrogen and 21% oxygen. oxygen.

The remaining 1% is made up of water The remaining 1% is made up of water vapor, argon, carbon dioxide, neon, helium, vapor, argon, carbon dioxide, neon, helium, and other gases.and other gases.

We call this entire mixture We call this entire mixture airair.. The most important of the air’s gases are The most important of the air’s gases are

oxygen and carbon dioxideoxygen and carbon dioxide

The AtmosphereThe Atmosphere

The Earth’s atmosphere also protects living The Earth’s atmosphere also protects living things from most of the sun’s harmful things from most of the sun’s harmful ultraviolet radiation.ultraviolet radiation.

At the same time, the atmosphere allows At the same time, the atmosphere allows visible light to reach the Earth’s surface, visible light to reach the Earth’s surface, supplying energy and making supplying energy and making photosynthesis possible.photosynthesis possible.

The atmosphere also radiates some heat The atmosphere also radiates some heat back to Earth, thereby warming the planet.back to Earth, thereby warming the planet.

The AtmosphereThe Atmosphere

The atmosphere is divided into 5 individual The atmosphere is divided into 5 individual layers. layers.

The layers become less dense the farther The layers become less dense the farther they are from earth’s surface.they are from earth’s surface.

1. Troposphere1. Troposphere

It extends from the earth’s surface to about It extends from the earth’s surface to about 6-10miles above the surface. 6-10miles above the surface.

It contains nearly 90% of the atmosphere’s It contains nearly 90% of the atmosphere’s gases.gases.

The air we breathe is part of the The air we breathe is part of the troposphere.troposphere.

It is also the layer in which most weather It is also the layer in which most weather occurs.occurs.

2. Stratosphere2. Stratosphere

The air in the stratosphere is less dense.The air in the stratosphere is less dense. Commercial airliners often travel in the lower Commercial airliners often travel in the lower

part of the stratosphere. part of the stratosphere. It contains the ozone layer, which protects It contains the ozone layer, which protects

us from harmful UV light from the sun.us from harmful UV light from the sun.

3. Mesosphere, 4. Thermosphere & 3. Mesosphere, 4. Thermosphere & 5. Exosphere5. Exosphere

The gases in these layers become thinner The gases in these layers become thinner and thinner until the exosphere merges with and thinner until the exosphere merges with outer space.outer space.

CLIMATECLIMATE

ClimateClimate

Weather is simply what is happening in the Weather is simply what is happening in the atmosphere at a particular place at a particular atmosphere at a particular place at a particular moment.moment.

Climate, on the other hand, is the average weather Climate, on the other hand, is the average weather in an area over a long period of time.in an area over a long period of time.

Important aspects of climate are: temperature, Important aspects of climate are: temperature, humidity, wind, and precipitation.humidity, wind, and precipitation.

Climate, particularly temperature and precipitation, Climate, particularly temperature and precipitation, determines what types of organisms are able to determines what types of organisms are able to live in a region.live in a region.

What determines climate?What determines climate?

Climate is determined by a variety of factors, Climate is determined by a variety of factors, including latitude, air circulation, ocean including latitude, air circulation, ocean currents, and the local geography of an currents, and the local geography of an area.area.

The most important of these factors is The most important of these factors is latitude.latitude.

LatitudeLatitude

Latitude is the distance from the equator, Latitude is the distance from the equator, measured in degrees north or south of the measured in degrees north or south of the equator.equator.

The equator is defined as 0The equator is defined as 0°.°. The most northerly latitude is the North The most northerly latitude is the North

Pole, at 90° north, while the most southerly Pole, at 90° north, while the most southerly is the South Pole, at 90° south.is the South Pole, at 90° south.

LatitudeLatitude

Latitude strongly Latitude strongly influences climate influences climate because of the amount because of the amount of solar energy an area of solar energy an area receives depends on receives depends on its latitude.its latitude.

More solar energy falls More solar energy falls on areas near the on areas near the equator that on areas equator that on areas closer to the poles.closer to the poles.

Atmospheric Circulation PatternsAtmospheric Circulation Patterns

There are three important properties of air There are three important properties of air that will help in the understanding of how air that will help in the understanding of how air circulation affects climate.circulation affects climate.

1. cold air sinks and warms as it sinks1. cold air sinks and warms as it sinks

2. warm air rises and cools as it rises2. warm air rises and cools as it rises

3. warm air can hold more water vapor than 3. warm air can hold more water vapor than cold air can.cold air can.

Atmospheric Circulation PatternsAtmospheric Circulation Patterns

Solar energy heats the ground, which Solar energy heats the ground, which warms the air above it. warms the air above it.

The warm air rises and cooler air moves into The warm air rises and cooler air moves into replace it.replace it.

Heating of the atmosphere therefore causes Heating of the atmosphere therefore causes wind, or the movement of air within the wind, or the movement of air within the atmosphere.atmosphere.

Because different latitudes receive different Because different latitudes receive different amounts of solar energy, the patterns of amounts of solar energy, the patterns of global circulation result.global circulation result.

Atmospheric Circulation PatternsAtmospheric Circulation Patterns

Ocean Circulation PatternsOcean Circulation Patterns

Ocean currents have a great effect on Ocean currents have a great effect on climate because water holds large amounts climate because water holds large amounts of heat.of heat.

The movement of surface ocean currents is The movement of surface ocean currents is caused largely by winds and the rotation of caused largely by winds and the rotation of the earth. the earth.

These currents redistribute warm and cool These currents redistribute warm and cool masses of water.masses of water.

Ocean Circulation PatternsOcean Circulation Patterns

Seasonal Changes in ClimateSeasonal Changes in Climate

The seasons are a result of the Earth’s orbit The seasons are a result of the Earth’s orbit around the sun.around the sun.

Seasonal Changes Seasonal Changes

The Earth is tilted at about 23The Earth is tilted at about 23° relative to the path ° relative to the path of its orbit.of its orbit.

This tilt means that the angle at which the sun’s This tilt means that the angle at which the sun’s rays strike the earth changes as the earth moves rays strike the earth changes as the earth moves around the sun.around the sun.

During spring and summer in the Northern During spring and summer in the Northern Hemisphere, the N. hemisphere tilts toward the Hemisphere, the N. hemisphere tilts toward the sun and receives concentrated, direct sunlight.sun and receives concentrated, direct sunlight.

During fall and winter, the situation is reversed.During fall and winter, the situation is reversed.

Seasonal Changes Seasonal Changes

The four seasons familiar to many people in The four seasons familiar to many people in the world do not occur in the tropics, which the world do not occur in the tropics, which are regions close to the equator.are regions close to the equator.

The temperatures are high and constant The temperatures are high and constant throughout the year because most areas throughout the year because most areas receive nearly direct sunlight year-round.receive nearly direct sunlight year-round.

Greenhouse EarthGreenhouse Earth

The Greenhouse EffectThe Greenhouse Effect

The Earth is similar to a greenhouse. The The Earth is similar to a greenhouse. The atmosphere acts like the glass.atmosphere acts like the glass.

As heat radiates up from the earth, some of As heat radiates up from the earth, some of it escapes into space.it escapes into space.

The rest of the heat is trapped by gases in The rest of the heat is trapped by gases in the troposphere and warms the air.the troposphere and warms the air.

This process is called the This process is called the GREENHOUSE GREENHOUSE EFFECT.EFFECT.

The Greenhouse EffectThe Greenhouse Effect

Not every gas in our atmosphere traps heat Not every gas in our atmosphere traps heat this way.this way.

The gases that do trap and radiate heat are The gases that do trap and radiate heat are called called greenhouse gases.greenhouse gases.

The major greenhouse gases are water The major greenhouse gases are water vapor, carbon dioxide, chlorofluorocarbons vapor, carbon dioxide, chlorofluorocarbons (CFCs), methane, and nitrous oxide.(CFCs), methane, and nitrous oxide.

After water vapor, carbon dioxide is the After water vapor, carbon dioxide is the most important of the greenhouse gases.most important of the greenhouse gases.

Carbon DioxideCarbon Dioxide

In 1958, a geochemist named Charles In 1958, a geochemist named Charles Keeling began to measure the amount of Keeling began to measure the amount of carbon dioxide in the earth’s atmosphere.carbon dioxide in the earth’s atmosphere.

He noticed that during the winter months, He noticed that during the winter months, carbon dioxide levels rose and during the carbon dioxide levels rose and during the summer months they dropped.summer months they dropped.

After only a few years of measuring, it was After only a few years of measuring, it was apparent that the levels were getting higher apparent that the levels were getting higher in the winter and not dropping as much in in the winter and not dropping as much in the summer.the summer.

Carbon DioxideCarbon Dioxide

What might be the cause of the rise and fall of the What might be the cause of the rise and fall of the level during the winter and summer months?level during the winter and summer months?

Plants use carbon dioxide to grow, so... Plants use carbon dioxide to grow, so... During summer months the levels drop and During summer months the levels drop and during the winter months they rise. It is in during the winter months they rise. It is in correlation with the amount of plant growth.correlation with the amount of plant growth.

Carbon DioxideCarbon Dioxide

Where is the extra Carbon Dioxide Where is the extra Carbon Dioxide coming from?coming from?

Fossil fuels come from plants that have been Fossil fuels come from plants that have been buried for millions of years.buried for millions of years.

These plants become coal, oil, or natural gas.These plants become coal, oil, or natural gas. When they are burned, they release the stored When they are burned, they release the stored

carbon as carbon dioxide.carbon as carbon dioxide. Millions of tons of carbon dioxide are poured into Millions of tons of carbon dioxide are poured into

the atmosphere each year.the atmosphere each year. There is also a significant release of carbon There is also a significant release of carbon

dioxide from the burning of large areas of forest.dioxide from the burning of large areas of forest.

Greenhouse gases and the Earth’s Greenhouse gases and the Earth’s temperaturetemperature

Since greenhouse gases trap heat near the Since greenhouse gases trap heat near the Earth’s surface, many scientists think that Earth’s surface, many scientists think that the increase in carbon dioxide has resulted the increase in carbon dioxide has resulted in an increase in Earth’s temperatures.in an increase in Earth’s temperatures.

This predicted increase in temperature is This predicted increase in temperature is called called GLOBAL WARMING.GLOBAL WARMING.

A Warmer EarthA Warmer Earth

Scientists are not sure how quickly the earth Scientists are not sure how quickly the earth will warm or how severe the effects will be.will warm or how severe the effects will be.

Different computer models give different Different computer models give different answers to these questions.answers to these questions.

A warmer EarthA warmer Earth

If the Earth heats up significantly, the If the Earth heats up significantly, the oceans will absorb more heat energy, which oceans will absorb more heat energy, which makes hurricanes and typhoons more makes hurricanes and typhoons more common.common.

Scientists are also concerned that the ocean Scientists are also concerned that the ocean currents may change, leading to droughts in currents may change, leading to droughts in some areas and major flooding in others.some areas and major flooding in others.

A Warmer EarthA Warmer Earth

As polar regions warm, more icebergs may As polar regions warm, more icebergs may break loose from glaciers and melt in the break loose from glaciers and melt in the sea.sea.

Sea levels would then rise, not only from Sea levels would then rise, not only from melting ice but also the water expands as it melting ice but also the water expands as it warms. warms.

As a result of higher sea levels, some As a result of higher sea levels, some coastal areas might be covered with water.coastal areas might be covered with water.

The Ozone ShieldThe Ozone Shield

The stratosphere contains the Earth’s ozone The stratosphere contains the Earth’s ozone shield.shield.

Ozone is a form of oxygen with molecules made of Ozone is a form of oxygen with molecules made of three oxygen atoms.three oxygen atoms.

Ozone absorbs most of the UV light from the sun.Ozone absorbs most of the UV light from the sun. UV light is very harmful to organisms because it UV light is very harmful to organisms because it

can damage the genetic material in living cells.can damage the genetic material in living cells. The ozone layer is like “sunscreen” for the earth.The ozone layer is like “sunscreen” for the earth.

Ozone EatersOzone Eaters

CFCs (chlorofluorocarbons) were thought to CFCs (chlorofluorocarbons) were thought to be miracle chemicals.be miracle chemicals.

They are nonpoisonous, nonflammable, They are nonpoisonous, nonflammable, non-corrosive metals.non-corrosive metals.

At Earth’s surface, CFCs are chemically At Earth’s surface, CFCs are chemically stable. stable.

CFCs are now known to destroy our CFCs are now known to destroy our protective ozone layer.protective ozone layer.

The Ozone HoleThe Ozone Hole

Data collected by satellites since 1979 Data collected by satellites since 1979 shows a significant decrease in the amount shows a significant decrease in the amount of ozone at the poles. of ozone at the poles.

As the amount of Ozone decreases, more As the amount of Ozone decreases, more UV light is able to pass through to Earth’s UV light is able to pass through to Earth’s surface.surface.

There are many detrimental effects of ozone There are many detrimental effects of ozone thinning and increased UV penetration.thinning and increased UV penetration.

The Ozone HoleThe Ozone Hole

Stopping Ozone EatersStopping Ozone Eaters

In 1987, the Montreal Protocol called for a In 1987, the Montreal Protocol called for a sharp decrease in the production of CFCs.sharp decrease in the production of CFCs.

In 1992, 93 countries decided upon the In 1992, 93 countries decided upon the following agreements:following agreements:

1.1. Industrialized countries must eliminate CFCsIndustrialized countries must eliminate CFCs2.2. Industrialized agreed to help developing Industrialized agreed to help developing

countries stop using CFCscountries stop using CFCs3.3. Banning of other substances that were also Banning of other substances that were also

harmful to the ozone.harmful to the ozone.