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Global Changes in the Global Changes in the AtmosphereAtmosphere

Climate, Global WarmingClimate, Global Warmingandand

Ozone DepletionOzone Depletion

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What Causes Climate?What Causes Climate?•““WeatherWeather” is the condition of ” is the condition of

the atmosphere the atmosphere at a certain at a certain place and timeplace and time

•ClimateClimate is the is the average average year-year-after-year after-year conditions conditions of of temperature, precipitation, temperature, precipitation, winds, and clouds in an areawinds, and clouds in an area

•Two Two main main factorsfactors determine determine climate: climate: temperature, temperature, precipitationprecipitation

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Global WarmingGlobal Warming• Over the last 120 years , the average Over the last 120 years , the average

temperature of the troposphere has temperature of the troposphere has risen by 0.5risen by 0.5° Celsius° Celsius

• Global WarmingGlobal Warming is the gradual is the gradual increase in the temperature of Earth’s increase in the temperature of Earth’s atmosphereatmosphere

• The Greenhouse EffectThe Greenhouse Effect is a natural is a natural process by which heat is trapped in the process by which heat is trapped in the atmosphere by water vapor, carbon atmosphere by water vapor, carbon dioxide, methane and other gases that dioxide, methane and other gases that form a “blanket” around the Earth.form a “blanket” around the Earth.

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Melting Glaciers/ Ice CapsMelting Glaciers/ Ice Caps

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Melting Glaciers/ Ice CapsMelting Glaciers/ Ice Caps

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Factors Affecting Factors Affecting TemperatureTemperature

• Main factors that influence Main factors that influence temperaturetemperature– LatitudeLatitude– AltitudeAltitude– distance from large bodies of waterdistance from large bodies of water– ocean currents.ocean currents.

• LatitudeLatitude is the distance from the equator, is the distance from the equator, measured in degrees.measured in degrees.

• Climates of areas farther from the equator Climates of areas farther from the equator tend to be cooler than areas close to the tend to be cooler than areas close to the equator.equator.

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Temperature ZonesTemperature Zones

• Tropical zoneTropical zone: From the equator, to : From the equator, to 23.5° North and South, climates are 23.5° North and South, climates are warm. Frequent direct sunlightwarm. Frequent direct sunlight

• Polar zonesPolar zones: Near poles, from 66.5° : Near poles, from 66.5° to 90° North and from 66.5° to 90° to 90° North and from 66.5° to 90° South, climates are coldSouth, climates are cold

• Temperate zonesTemperate zones: From tropical : From tropical zone to polar zones (23.5°-zone to polar zones (23.5°-66.5°North and South). Climates in 66.5°North and South). Climates in these areas vary from having warm these areas vary from having warm or hot summers to having cool or or hot summers to having cool or cold winterscold winters

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Prevailing WindsPrevailing Winds

• WindsWinds that blow that blow mainly from one mainly from one direction.direction.

• These winds influence an area’s These winds influence an area’s moisture and temperature.moisture and temperature.

• These These affectaffect the amount of the amount of precipitation precipitation an area receivesan area receives– From moist, wet area – rainFrom moist, wet area – rain– From dry, cool areas – very little From dry, cool areas – very little

rainrain

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Prevailing Winds and Prevailing Winds and PrecipitationPrecipitation

• A mountain range in the path of A mountain range in the path of prevailing winds can influence prevailing winds can influence where precipitation fallswhere precipitation falls

* When humid winds blow * When humid winds blow from the ocean toward a from the ocean toward a mountain range the air is forced mountain range the air is forced to rise up the mountains. The to rise up the mountains. The warm humid air cools and warm humid air cools and condenses this forms clouds and condenses this forms clouds and maybe rain or snowmaybe rain or snow

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Windward and LeewardWindward and Leeward• Rain or snow tends to fall on the Rain or snow tends to fall on the

windwardwindward sideside of the mountain, the of the mountain, the side that the wind hits firstside that the wind hits first

• The The leeward sideleeward side of the mountain, of the mountain, which is which is downwind from the downwind from the windwardwindward, side is in a “rain shadow”. , side is in a “rain shadow”. – The air on the The air on the leeward sideleeward side tends tends

to be to be drierdrier than the windward side, than the windward side, where the rain or snow falls, after where the rain or snow falls, after being removed from the humid being removed from the humid windwind

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SeasonsSeasons

•Most places on Earth outside of Most places on Earth outside of the tropics have four seasonsthe tropics have four seasons– WinterWinter– SpringSpring– SummerSummer– Autumn (fall)Autumn (fall)

•EarthEarth is is tilted tilted at an angle of at an angle of 23.523.5°° on its axis. on its axis.

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The Reason for Seasons!The Reason for Seasons!

• Seasons Seasons are are causedcaused by the by the tilt tilt of of Earth’s axis as Earth travels around Earth’s axis as Earth travels around the sun.the sun.

• Axis Axis – the imaginary line that passes – the imaginary line that passes through Earth’s center and the N.& S. through Earth’s center and the N.& S. PolesPoles

• Because of this tilt the Sun’s rays hit Because of this tilt the Sun’s rays hit the:the:– Equator more directlyEquator more directly– Poles at an anglePoles at an angle

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DaysDays• Earth’s Earth’s rotation (spinning on its rotation (spinning on its

axis)axis) causes day and nightcauses day and night..

• Earth rotatesEarth rotates from from West to EastWest to East (Sun rises in the east and sets in (Sun rises in the east and sets in the west) counterclockwise.the west) counterclockwise.

• Each rotation takes Each rotation takes approximately approximately 24 hours.24 hours.

• We know all this because ofWe know all this because of Astronomy, the study of the Astronomy, the study of the moon, stars, and other objects in moon, stars, and other objects in space.space.

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Rotation…Rotation…Rotation…Rotation…RotationRotation

• The Earth rotates on its axis at a The Earth rotates on its axis at a speed of 30 km/sec.speed of 30 km/sec.

• 1,600 km/hour or 2,580 mph!1,600 km/hour or 2,580 mph!

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YearsYears• The Earth travels on a The Earth travels on a path around path around

the Sun called an orbit.the Sun called an orbit.

• As the Earth rotates it also revolvesAs the Earth rotates it also revolves

• Revolution Revolution is the movement of one is the movement of one object around another object.object around another object.

• The The EarthEarth takes about takes about 365.25 days365.25 days or one year to or one year to revolve around the revolve around the sunsun..

• The Earth’s orbit is like a flattened The Earth’s orbit is like a flattened circle, not perfectly round.circle, not perfectly round.

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Earth’s TiltEarth’s Tilt

• When the When the north endnorth end is is tiltedtilted toward the toward the SunSun, it is , it is summersummer in in the the Northern HemisphereNorthern Hemisphere (winter (winter in Southern Hemisphere)in Southern Hemisphere)

• When the When the southern endsouthern end it it tiltedtilted toward the toward the SunSun, it is , it is summer in summer in the Southern Hemispherethe Southern Hemisphere (winter in Northern Hemisphere)(winter in Northern Hemisphere)

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CalendarCalendar• Since the orbit takes 365.25 days, Since the orbit takes 365.25 days,

we have adjusted our calendar to we have adjusted our calendar to make up for the ¼ day. We use make up for the ¼ day. We use the Roman Calendarthe Roman Calendar

• Every Every 4 years4 years we have a we have a Leap YearLeap Year. . The leap day is February 29 The leap day is February 29thth!!

• This year was a Leap Year (2008).This year was a Leap Year (2008).• Other years always have Other years always have

– 7 months – 31 days7 months – 31 days– 4 months – 30 days4 months – 30 days– 1 month – 28 days1 month – 28 days

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Summer and WinterSummer and Winter

• Summer and Winter are Summer and Winter are NOT NOT affectedaffected by changes in by changes in Earth’s Earth’s distance from the Sundistance from the Sun

• Earth is at its Earth is at its greatest distancegreatest distance from the Sun from the Sun during the during the summersummer!!

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SolsticesSolstices• Two days each year when the Two days each year when the

noon Sun is directly overhead in noon Sun is directly overhead in the N. Hemisphere at 23.5the N. Hemisphere at 23.5° N or ° N or 23.523.5° S° S

• Winter SolsticeWinter Solstice - - in the Northern in the Northern Hemisphere, the Sun is overhead at Hemisphere, the Sun is overhead at this angle onthis angle on December 21December 21stst (we (we have shortest day)have shortest day)

• Summer SolsticeSummer Solstice - - in the summer in the summer (Northern Hemisphere), the Sun is (Northern Hemisphere), the Sun is overhead at this angle onoverhead at this angle on June 21June 21st st

(we have longest day)(we have longest day)

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EquinoxEquinox

• Means Means equal equal day and equal night!day and equal night!

• When the noon Sun is directly When the noon Sun is directly overheadoverhead at the at the equatorequator

• Occurs two times per year when we Occurs two times per year when we have have 12 hours12 hours of of daylightdaylight and and 12 12 hourshours of of darknessdarkness

• Vernal Equinox (spring)Vernal Equinox (spring) – March – March 21st21st

• Autumnal EquinoxAutumnal Equinox (fall)(fall) – – September 23rdSeptember 23rd

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ADD MOON PHASES, Eclipses, ADD MOON PHASES, Eclipses, TIDESTIDES

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Ozone DepletionOzone Depletion

• Ozone is a gas in the stratosphere, a Ozone is a gas in the stratosphere, a high layer of the atmosphere, that high layer of the atmosphere, that absorbs most of the ultraviolet radiation absorbs most of the ultraviolet radiation that strikes Earth from the sun.that strikes Earth from the sun.

• Chemicals produced by humans Chemicals produced by humans have been damaging the ozone have been damaging the ozone layer, chloroflourocarbons (CFC’s) layer, chloroflourocarbons (CFC’s) are the main cause.are the main cause.

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