CHAPTER 17 Weather and Climate - Mr. Barrow's Science Center

CHAPTER 17 Weather and Climate - Mr. Barrow's Science Center

Start-Up ActivitiesAtmospheric PressureChanges in atmospheric pressure are involvedin producing winds and weather. You maynot be aware of how much pressure theatmosphere exerts, but you can see it in thisLab.1. Fill a glass to the brim with water.2. Place a piece of thick paper or cardboardon top.3. Hold the paper or cardboard securely tothe brim of the glass. Turn the glassupside down.4. Release your hand from the paper5. Think Critically What keeps the paperor cardboard against the brim of the glassand the water from flowing out?STEP 1STEP 2STEP 3STEP 4Weather and Climate Makethe following Foldable to compareand contrast the characteristicsof weather and climate.Fold one sheet of paper lengthwise.Fold into thirds.Unfold and draw overlapping ovals.Cut the top sheet along the folds.Label the ovals as shown.Weather Both ClimatePreview this chapter’s contentand activities atgpescience.comConstructing a Venn Diagram As you readthe chapter, list the characteristics unique toweather under the left tab, those unique to climateunder the right tab, and those elementscommon to both under the middle tab.517Byron Aughenbaugh/Getty Images

Earth’s AtmosphereReading Guide■ Describe the composition of theatmosphere.■ Explain how the atmosphere isheated and include the role ofland surface and water.■ Describe Earth’s system of watercycling.Heat and water are essential for lifeon Earth.Review Vocabularynucleus: a central point aboutwhich concentration or accretiontakes placeNew Vocabularytropospheretemperature inversion•greenhouse effectlatent heatAtmospheric CompositionYou probably never think about the air you breathe. Yourbody uses only oxygen, but air is a mixture of gases. Nitrogen isthe largest component with 78 percent and oxygen is next with21 percent by volume. Most of the remaining one percent is theinactive gas argon and water vapor in varying amounts. Thesmall remaining portion is a mixture of trace gases, so calledbecause they are present in such small, barely detectableamounts. For example, carbon dioxide makes up only about0.03 percent, and the other trace gases—methane, nitrous oxide,and ozone—together make up less than 0.001 percent of theatmosphere. Still, these trace gases are critical for life on Earth.What are the trace gases?CO 2 Concentration(ppm)Figure 1 In northern latitudes,carbon dioxide concentrationincreases during summer anddecreases during winter.360350340330Comparison of CO 2 Concentration toTime of Year and Latitude1982 1983 1984Biological Processes Living organisms produce tracegases, except ozone. Cellular respiration by organisms produceswater vapor and carbon dioxide (CO 2 ). Photosynthetic organismsuse carbon dioxide and produce almost all the oxygen in-90S090NLatitudethe atmosphere. Organisms alter atmosphericCO 2 concentration at various latitudesthroughout the year, as shown inFigure 1. Microorganisms in swamps,rice paddies, and soil produce nitrogenand methane. The microorganisms in thedigestive tracts of animals such as termites,cows, and sheep produce methane.518 CHAPTER 17 Weather and Climate

Figure 5 Earth’s continualcycling of water strongly affectsweather and climate.Plants Transpiration isthe loss of water throughpores in the leaves ofplants. More than 90 percentof the water thatenters a plant returns tothe atmosphere throughthe process of transpiration.Research howhumidity and air temperatureaffect transpirationrates in plants. Shareyour findings with yourclass.Global Water CyclePrecipitation, runoff, storage, and evaporation make up theglobal water cycle, shown in Figure 5. Plants are an importantpart of the water cycle. They affect absorption and runoff andreturn water to the air by evaporation from their surfaces.People affect the water cycle in many ways. They use groundwaterfor irrigation or pump it from wells. They replace forestswith agricultural fields and pave land to build cities. Many ofthese changes have reduced water quality and resources.Conserving water resources requires careful planning.SummaryAtmospheric•StructureThe stratosphere and the troposphere are twolower layers of Earth’s atmosphere. Mostweather takes place in the troposphere.•Atmospheric HeatingMost solar radiation first heats Earth’s surface,•which then heats the atmosphere.Characteristics of the land surface greatlyinfluence atmospheric heating.•Water in the AtmosphereCloud formation generally requires moist air,•rising and cooling, and condensation nuclei.Water is cycled through Earth’s system by precipitation,runoff, storage, and evaporation.Self Check1. Describe how temperature of the atmosphere changeswith height and explain why.2. Explain the greenhouse effect.3. Explain why small changes in the amount of tracegasses are so important in heating Earth’s atmosphere.4. Identify what must happen before rain can occur.5. Compare and contrast cumulus and stratus clouds.6. Think Critically How might changes on Earth’s surface,such as deforestation, have an effect on weather?7. Use Percentages If the southern hemisphere contains10 percent land and the northern hemisphere containsroughly 40 percent land, what percent of Earth is land?522 CHAPTER 17 Weather and ClimateMore Section Review

Visualizing aTemperature nversionNormally temperature decreases with increasingaltitude in the troposphere. Sometimesnear the ground, a temperature inversionoccurs and air becomes very stable and resistsrising. This can result in fog or smog in cities.Will a liquid behave in the same manner as theatmosphere?Real-World ProblemHow can you visualize what happens during atemperature inversion?Goals■ Make a model that demonstrates atemperature inversion.■ Apply what you observe to explain whathappens in the atmosphere during atemperature inversion.Materials10-mL beaker containing 2–3 mL water500-mL beaker containing 250 mL water1,000-mL beaker containing 750 mL waterfood coloringladlelong-stem dropperthermal mittfreezerhot plateSafety Precautions2. Add one to two drops of food coloring to thewater in the 10-mL beaker and let it standat room temperature.3. Heat 250 mL of water in the 500-mL beakerto near boiling.4. Hold the ladle at the surface of the chilledwater. Very slowly pour all the heated waterinto the ladle and allow it to slowly flow outof the ladle onto the surface of the chilledwater. You should have a bottom layer ofcold water and a top layer of hot water.5. Use the long-stem dropper to inject a fewdrops of the colored water from step 2 intothe cold water in the 10-mL beaker.Conclude and Apply1. Describe what happened to the coloredwater.2. Explain why this happened in terms of thetemperatures of the water layers.3. Infer how this is related to temperatureinversions in the atmosphere.Procedure1. Chill 750 mL of water in a 1,000-mL beakerto near freezing.Write a brief paragraph describing yourexperiment and your observations. Includea labeled diagram showing the temperaturelayers and explain what happened to thecolored water.LAB 523

WeatherReading Guide■ Explain what causes Earth’smajor wind and pressure systems.■ Describe typical daily weatherpatterns around lows and fronts.■ Describe the most importantstorm systems and forms ofsevere weather.Weather affects the health, life, andlivelihood of everyone on Earth.Review Vocabularygradient: the rate of change of aquantity with distanceNew Vocabularywesterliesjet stream•subtropical highweather frontFigure 6 In the northern hemisphere,four major pressure beltsproduce three major wind belts.Infer How does pressure affectwind direction?Polar easterliesWesterliesNortheasttradesSoutheasttradesWesterliesLHHLLHLHHHAtmospheric PressureAlthough you usually are unaware of it, the atmospherepresses down on you with a pressure equivalent to one kilogramper square centimeter. This pressure is caused by gas moleculesmoving and colliding with each other and any surfaces theytouch. Because the number of air molecules decreases as altitudeincreases, pressure always decreases with altitude. This is why airis said to be thinner in the upper atmosphere. The number of airmolecules, including oxygen, decreases in proportion to pressure.This is why jet aircraft cabins are pressurized and whyclimbers can get mountain sickness at altitudes over 3,000 m.Global Winds and Pressure Systems Weather patternsresult from complex global patterns of wind and pressure.Figure 6 shows a simplified picture of the Earth’sPolar highSub-polar lowLLHHLSubtropicalhighEquatoriallowmajor pressure belts that give rise to major windbelts. The most important of these are thewesterlies—winds that blow from the west in themiddle latitudes—and the trade winds, whichblow from the east, in the tropics.Two factors produce these global patterns—unequal heating between the equator and polesand the rotation of Earth. Warm air rising nearthe equator and sinking over the poles createsgeneral north-south wind circulation. Earth’srotation produces an east-west deflection of thisgeneral circulation pattern.524 CHAPTER 17 Weather and Climate

Jet Streams Imbedded in these wind systems are fast andpowerful jet streams that control many weather processes, suchas storm development. Most important for the United States isthe polar front jet stream, a wind maximum in the westerlieslocated about 12 km above the surface. Its speeds can exceed500 km/h. Major storm tracks follow it as it moves north andsouth with the seasons.High and Low Pressure SystemsThe large-scale weather systems that have the most effect onthe United States are the subpolar lows, westerlies, and the subtropicalhighs. Subtropical highs are relatively stable belts of highpressure near latitudes of 30°. In contrast, sub-polar lows and thewesterlies tend to meander as smaller cells of high and low pressuredevelop. The lows generally develop from a disturbance inthe polar front jet and move eastward with the jet stream.Specific patterns of weather are associated with high and lowpressure cells because of the way air flows around them. In thenorthern hemisphere, winds blow counterclockwise around lowsand clockwise around highs, as shown in Figure 7. In the southernhemisphere, the directions reverse. Lows are associated withrainfall and storms, and highs with calm winds and clear skies.Coriolis Effect Airflow around low orhigh pressure areas results from the netforces acting on the air. First, the pressure gradient pulls the airtoward low pressure. Then an apparent force, called the Corioliseffect, deflects the air to the right in the northern hemisphere.When these forces are balanced, air flows perpendicular to linesof equal pressure. Near the surface, friction slows air and modifiesits direction, turning it slightly toward low-pressure centersand slightly away from high-pressure centers. This causes air torise in the center of lows and to sink in the center of highs.Modeling the CoriolisEffectProcedure1. Put a large, round pieceof cardboard or paper ona turnable surface such asa turntable.2. Hold a ruler just above thediameter of the cardboard.3. Ask someone to turn thesurface while you draw aline across the turningcardboard with your penor pencil against the ruler.4. Repeat step 3 but turn thesurface in the oppositedirection.Analysis1. Compare the outlinesdrawn on the cardboard.2. Explain how these outlinesrepresentthe Corioliseffect.RisingairSinkingairLHFigure 7 At Earth’s surface in thenorthern hemisphere, air moves counterclockwisetoward low pressure andclockwise from high pressure.Infer How does air move when it is highabove Earth’s surface, above each pressuresystem?SECTION 2 Weather 525

Figure 8 The symbols shownbelow each of these weather frontsare used by meteorologists torepresent the respective frontson weather maps.Air Masses and Weather FrontsWeather around low-pressure cells is produced by interactionof air masses—large units of air with relatively uniformmoisture and temperature. These form when air remains stationaryfor a time, such as in regions of high pressure. The airthen takes on the characteristics of the surface. Air masses canbe polar or tropical and continental or maritime. Continentalair originates over land. It is relatively dry and can be extremelycold or extremely warm. Maritime air masses are moist becausethey originate over the oceans. The maritime air masses affectingthe United States come from the Atlantic Ocean, the PacificOcean, or the Gulf of Mexico.Air masses interact in zones called weather fronts, as shownin Figure 8, which are associated with low pressure systems.Warm and cold fronts create different types of precipitation. Ina warm front, warm air rises gently above the cold air, usuallyforming layered, stratus-type clouds or fog—a cloud with itsbase on the ground. Most layered clouds produce only drizzle orsteady rain. In a cold front, cold air pushes the warm air aloft ina random and chaotic fashion forming cumulus clouds. Theseoften produce showers and thunderstorms.What are weather fronts?Warm airCold airWarm airCold airCold frontWarm frontWarm airCold airWarm airCold airCool airStationary frontOccluded front526 CHAPTER 17 Weather and Climate

Severe WeatherThe continental United States is prone to severe weatherbecause of the extreme temperatures of warm and cold airmasses and the availability of moisture from tropical oceans.Such conditions lead to severe thunderstorms, hurricanes, tornadoes,and violent wind storms called downbursts.Thunderstorms Recall that cumulonimbus clouds formedfrom unstable air produce thunderstorms. A typical cumulonimbuscloud has ice crystals near its top, as shown in Figure 9.Sometimes these ice crystals act as nuclei to trigger furthergrowth of cloud droplets, and turbulence adds layers of ice duringmany cycles of sinking and rising. This forms hail. Hailstonescan grow to the size of softballs and can cause extensive damageto crops and structures.Downdrafts and Squalls The force of the falling precipitationin a thunderstorm may pull with it cold air bursts fromhigher in the cloud. This is why the air often feels cool after athunderstorm. This sinking current of cold air is called adowndraft. When a downdraft hits the surface with particularlystrong force, it spreads out in aseries of windy gusts called squalls.In arid regions, squalls producedust storms.Figure 9 When hailstones fall,they are repeatedly caught inupdrafts, coated with moisture,and frozen. This gives them alayered, onionlike appearance.Infer Why does this cumulonimbuscloud have an anvil-shaped top?Upper air flowDownbursts Cold air downdraftscan produce even more severeforms of weather. One example ofan extreme form of wind shear is adownburst. Here, cold air descendsfrom a thunderstorm and hits theground. When it hits the ground, itbursts outward like the spokes on awheel. The rapid change in windspeed and/or direction that a downburstcauses can be dangerous foraircraft during both take-off andlanding. The winds that result fromdownbursts can be as high as260 km/h. Fortunately, automatedwarning systems now alert pilots tolook for signs of downbursts whenapproaching an airport.12 kmDowndraftUpdraftAnvil topStorm travelSECTION 2 Weather 527

Topic: Hurricane TrackingVisit for Weblinks to information abouthurricanes and hurricane tracking.Activity Research six hurricanes.Make a table that lists how eachwas tracked as a tropical depressionand then as a hurricane.Figure 10 Texas, Oklahoma,and Kansas frequently experiencetornadoes.Fewerthanten101010Scale0 500 mi 100 1000 km10 10501002003005010010050Tornadoes and Hurricanes Two types of violent windstorms that differ greatly in their origins and effects aretornadoes and hurricanes. Tornadoes are intense, short-lived,localized storms in the mid-latitudes. They originate in cumulonimbusclouds under special conditions. Typically, tornadoesthat occur in the United States form when dry air from thedeserts of Mexico and the southwest overrides warm, moist airfrom the Gulf of Mexico. This happens frequently in the GreatPlains, the lower midwest, and parts of the south, as shown inFigure 10. In the south, they often accompany hurricanes.A twisting, funnel-shaped tornado cloud can move acrossland at a speed of around 50 km/h creating a path 150 m wideand 10 km long. Intense, circular winds in the funnel can reachspeeds up to 400 km/h. The extreme low pressure at the centercan result in more damage than that from the wind.Hurricanes are tropical storms that cover vastFewer thanten1010050505010areas and last for days. Those affecting the UnitedStates often form as tropical depressions over thewarm waters of the southern Atlantic off thecoast of Africa. When winds exceed 118 km/h, thestorms are called hurricanes. A typical hurricaneconsists of vast cloud bands that spiral inwardtoward the clear center, called the eye. Scientistsoften fly into the eye to study the storm. WesternPacific hurricanes are called typhoons.SummaryGlobal•Wind and Pressure SystemsFour major pressure systems produce threemajor wind systems in each hemisphere.•High and Low Pressure SystemsAir flows counterclockwise around lowsand clockwise around highs in the northern•hemisphere.Air rises in the center of lows and sinks in thecenter of highs.Weather Fronts and Severe Weather•Air masses interact at weather fronts.Warm fronts are associated with stratus-typeclouds and cold fronts with cumulus-type•clouds.Severe weather includes hurricanes, tornadoes,and downbursts.Self Check1. Explain how Earth’s rotation affects winds.2. Compare and contrast tornadoes and hurricanes.3. Infer the wind directions around a high in the southernhemisphere.4. Describe common differences between continental airmasses and maritime air masses.5. Compare and contrast warm fronts and cold fronts.6. Think Critically If the polar front jet stream were tomove southward over the U.S., what other weathersystems are likely to be affected?7. Use Percentage A tornado watch was issued on25 days during one year in a midwest city. Whatpercent of the year does this represent?528 CHAPTER 17 Weather and ClimateMore Section Review

ClimateReading Guide■ Describe what determinesclimate.■ Explain how latitude, oceans, andother factors affect the climate ofa region.■ Classify climate systems.■ Describe climate distribution overthe United States.Climate affects the way you live.Review Vocabularyboreal: relating to northern regionsNew Vocabularybiospherecontinental climatemaritime climate•lee rain shadowsea breezeClimate and WeatherWhat is the climate where you live? Traditionally, climatemeans the long-term average of weather conditions—wind,temperature, precipitation, moisture, and other aspects ofweather. Climate also describes the annual variations of theseconditions and their extremes.Averages of data collected monthly over 30 years or longer areused to define climatic normals. These normals do not describeusual weather conditions of an area, but are only averages of conditionsmeasured at one local site. For example, theconditions in a city might vary from what is measuredat an airport weather station outside the city.Figure 11 All of the five spheresshown below interact. Each spherecauses changes in, and is changedby, the others.Research What does the prefixcryo- mean?SpaceClimate System Climate is best considered aspart of the whole Earth system. This biogeophysicalsystem can be visualized as five spheres thatinteract to create the environments in which welive, as shown in Figure 11. The atmosphereincludes the air around us. The biosphere iseverything organic, including plants, animals,and humans. The hydrosphere is liquid water inoceans, lakes, rivers, soil, and underground. Thecryosphere is frozen water in snow, ice, and glaciers.Finally, the lithosphere is the solid Earth,including its soil, rocks, and mantle.AtmosphereBiosphereCryosphereHydrosphere LithosphereSECTION 3 Climate 529

Topic: World ClimatesVisit for Weblinks to data on mean annualtemperature and rainfall ofworld cities.Activity Use a world atlas,globe, or large classroom map tofind a city corresponding to eachof the eight climate divisionsshown in Figure 17.Sphere Interactions Gases, water, soluble materials, energy,and particulates are exchanged among these spheres. Eachsphere affects all the other spheres. For example, volcanic eruptionstransfer gases and particles from the lithosphere to theatmosphere. The atmosphere provides and regulates theamount of water in the hydrosphere and cryosphere, and provideswater, carbon, and oxygen for the biosphere. Throughwinds, atmosphere causes erosion, creates soil, and absorbs andemits energy from the Sun. When you consider all these complexinteractions, you can see why it’s better to define climate asthe average weather conditions, their variability and causes, andinter-relationships of many individual systems within the globalEarth system. One example how such systems are inter-related isillustrated in Figure 12.What causes climate?Latitude is the primary factor that determines climate at agiven location. The amount of radiation received from the Sunand the prevailing circulation features depend on latitude. Otherfactors are location near high mountains or on the east or westsides of a continent and distance from major bodies of water.Causes of Mean Temperature The amount of solar radiationreceived and surface temperatures vary greatly from theequator to the poles. In the winter, the amount of solar radiationvaries, because of the low angle at which it strikes Earth. As aresult, temperatures decrease rapidly with increasing latitude.The high reflectance, or albedo, of snow and ice in high latitudesadds to this decrease. In summer, temperature decrease is lesspronounced as sunlight strikes at a higher angle and periods ofdaylight are longer. The temperature patterns over the UnitedStates illustrate this, as shown in Figure 12. The strong temperaturegradients in winter and spring help to create storms andsevere weather.-25-30-35510Figure 12 Lines drawn on aweather map that connect pointsof equal temperature are calledisotherms.Infer Why are warmer temperaturesshifted northward in July?January–20–15–10–50155 10201520 25 30July152025530 CHAPTER 17 Weather and Climate

NGS VISUALIZING TITLE EARTH’S BIOGEOPHYSICAL SYSTEMFigure 13The Namib desertillustrates theinterconnectednessof climate, geology,plants, and animals. It iscreated by high pressure,wind, and cold oceancurrents along the westcoast of southern Africa.The desert is constantly reshaped by the wind.Transverse dunes show that the wind blows inone preferred direction. Dunes also beginwhen isolated plants trap sand. However,most deserts are not covered with sanddunes—they are made of stony pavement leftbehind when wind strips the desert surface.Winds and water remove the finer surfacematerials, leaving stones behind. This processis called deflation.Dense coastal fog forms when the air above cold ocean currentsinteracts with moist desert air. Although deserts may appear to bedry, the air above ground contains lots of moisture. Condensationfrom fog produces fog-water, which drips into desert pavement anddissolves rocks, forming new sediment. It also forms small poolsbelow the stony surface, which support plant growth. Desert plantshave special adaptations such as a dense, compact form and thick,waxy coats. This helps protect them from both heat and animals.Transverse dunesform perpendicularto the wind.Star-shaped dunesform when windsare variable.Stone pavement ismore common in adesert than dunes.Beetles capture fog-water by basking upside down orforming trenches at the bottom of dunes. They alsosurvive beneath the leaves of Welwitschia plants wheretemperatures may be 30°C cooler than the surroundbare ground.The Welwitschia plant grows in this barren land by absorbingfog-water through its elongated leaves. It is a relic ofmillions of years ago and is found only in the Namib.SECTION 3 Climate 531(cw from top) (1)Cartesia/Getty Images, (2,3)Bernhard Edmaier/Photo Researchers, (4)Michele Westmorland/CORBIS, (5)Wendy Dennis/Visuals Unlimited, (6)Anthony Bannister/CORBIS

Ocean and Land Influence Oceans and ocean currentsmodify the basic climate. Areas with little direct ocean influenceare called continental climates and have steep temperaturegradients. A climate with strong ocean influence is calleda maritime climate. Maritime climates are milder—summersare cooler, winters are warmer, and daily temperatures varyless. The continental climate of Peoria, Illinois, and the maritimeclimate of San Francisco, California, illustrate the contrast.Although both are near 40° N latitude, the temperaturedifference between the warmest and coldest months is about8° C in San Francisco and 30° C in Peoria. Maritime effects arestrong enough to keep winters at arctic Spitsbergen, Norwayat 78° N latitude, warmer than in International Falls,Minnesota at 48° N latitude.Figure 14 Lines drawn on amap that connect points of equalprecipitation are called isohyets orisohyetal lines.Research What does the prefixiso- mean?10050200Tropic of Cancer3010010050103030Precipitation Wind and pressure patterns determine precipitation.Humid climates are associated with low-pressure areasin the tropics and the middle latitudes. Rainfall is greater near theequator because the trade winds of both hemispheres convergethere, increasing the rising motion. Arid climates are commonwhere high pressure prevails, and aridity is particularly intense inthe subtropics on the eastern sides of the subtropical highs.Superimposed upon this general pattern are differencesrelated to location on a continent, as shown for North America inFigure 14. The west coast lies east of the subtropical high, whichbrings cold water currents and stable air. This creates the dry climatesof California and the southwest. The east coast lies west ofthe subtropical high, where southerly winds bring warm, unstableair from the Gulf of Mexico that increases precipitation. Airmasses can also influence the amount of precipitation an areareceives. When continental polar air masses, which originate inthe cold, dry artic regions,move across the Midwesternstates in the winter, cold, dry50100200100 1005010010Centimetersabove 5005002001005030100weather results.Another factor affectingprecipitation is the prevailingwinds. Because westerliesprevail in the middle latitudes,the maritime influenceis stronger on the westcoast. This explains why SanFrancisco has a stronglydeveloped maritime climate,but Boston has a continentalclimate.532 CHAPTER 17 Weather and Climate

Influence of Mountains The Rocky Mountains and the SierraNevada also influence the climate of the west. They act as barriersin the wind, blocking weather systems and altering patterns ofprecipitation. When the wind blows perpendicular to one side ofa mountain range, a lee rain shadow forms on the opposite side,as shown in Figure 15. The Great Plains lie in the lee shadow ofthe Rocky Mountains and are relatively dry.Influence of Water Coasts and lakeshores can affect regionalclimates in several ways. In winter, lake-effect snow oftenresults in regions around the Great Lakes, like those shown inFigure 16. As cold, continental air from the north passes overwarmer lake water, the air mass gains heat and moisture. Whenthe air mass reaches the colder land to the south or east of a lake,heavy precipitation, in the form of snow, occurs.Another example of how coasts affect regional climate is asea breeze. A sea breeze (or lake breeze) blows from the watertoward the land in the afternoon, when the land is warmerthan the water. Warm air rises over the land creating lowpressure that allows cool, dense air to blow from the sea towardland. The reverse happens at night when the land is cooler thanthe water. A land breeze occurs when cool, dense air over landcreates high pressure causing the air to blow from the landtoward the sea.Climate Scale Many small-scale variations are superimposedupon the large-scale climate patterns. Some are regionalor local and others, termed microclimates, are variations withinsmall distances. For example, cities create a condition called theheat island effect. Building and pavement materials heat morerapidly than bare land. Vehicles and industry produce pollutionthat retains heat. Air rises over a heat island, pulling in air fromthe surrounding countryside. On some clear, calm nights,downtown San Francisco can be as much as 8°C warmer thanthe surrounding rural areas.Figure 15 The lee rain shadowof the Sierra Nevada and RockyMountains accounts for much ofthe decreased precipitation shownin Figure 14.Figure 16 People often experiencesimilar weather events nearlarge bodies of water. Cities east ofthe Great Lakes experience lakeeffectsnow.LakeMichiganLakeSuperiorLakeHuronLake ErieLakeOntarioSECTION 3 Climate 533

ColdAridColdDry winterWarmAridWarmSemi-aridWet winterDry summerWet summerDry winterWarmWetWarmWettundraborealevergreen forestdesertgrasslandMediterraneanforesttemperatewoodlandsubtropicaldeciduous foresttropicaldeciduous forestFigure 17 Climate zone influencesthe types of vegetation thatwill grow there.Infer What are two major factorsthat characterize climate types?706050403080180 160 140 120 100 80 60 40 20Types of ClimatesGeographer Glenn Trewartha and meteorologist LyleHorn designed a system to classify climates, shown in Figure 17.It has three major divisions—cold or boreal, arid and semi-arid,and climates with adequate heat and precipitation. The lastincludes temperate, subtropical, and tropical climates. Thesedivisions are closely correlated with vegetation.SummaryClimateand WeatherClimate is the net result of interactionsinvolving all aspects of the biogeophysicalsystem called Earth.•What causes climate?The main causes of climate are thedistribution of solar radiation and the•location of pressure and wind systems.Oceans, land masses, mountains, and large•lakes also affect climate.Climates are classified on the basis of•temperature and moisture availability.Prevailing high pressure or the rain shadow ofmountains can produce dry climates.•Types of climateClimates can be classified into three majordivisions.Self Check1. Explain why a climatic normal does not tell you exactlywhat to expect where you live.2. Identify the five elements of the biogeophysical systemcalled Earth.3. Explain the association between climate and latitude.4. Compare and contrast continental and maritimeclimates.5. Think Critically Would you expect the daily temperaturerange to be greater in a maritime climate or acontinental climate? Explain.6. Calculate Range The coolest average summer temperaturein the United States is 2°C at Barrow, Alaska,and the warmest is 37°C at Death Valley, California.Calculate the range of average summer temperaturesin the United States.534 CHAPTER 17 Weather and ClimateMore Section Review

Earth’s Changing ClimatesReading Guide■ Explain how climate changesseasonally.■ Explain causes of climate change.■ Describe how we influence climate.■ Explain El Niño’s effect on weather.Changing climates affect all lifeon Earth.Review Vocabularytrace: a minute, barely detectableamount presentNew Vocabulary•global warmingEl NiñoLa Niña•Seasonal ChangesSeasonal changes occur as Earth completes a revolutionaround the Sun. The hemisphere tilted toward the Sun experiencessummer while the hemisphere tilted away from the Sunexperiences winter. During the summer, a hemisphere receivesmore intense solar radiation and temperatures rise. Duringwinter, the intensity and amount of solar radiation decreasesand temperatures drop. Seasonal changes are magnified in themid-latitudes by the temperature contrast between land andoceans. The oceans are generally colder than land in the summer,but warmer than land in the winter.Long-term ChangesCycles of glaciations, called ice ages, represent long-termclimatic change. The peak of the last ice age was 18,000–22,000years ago when global was about 6°C cooler than present.Glaciers covered much of the middle and highlatitudes, as shown in Figure 18A. Deserts expanded inthe tropics and rainforests all but disappeared.However, by 5,000 years ago, most of the glacial icehad melted, rainforests returned, and grasslands spreadinto low latitude deserts. World climate reached its currentpattern only about 3,000 years ago, but even sincethen, large variations have occurred. In the Medievalperiod, parts of the northern hemisphere were warmand much of the North Atlantic was free of ice, enablingthe Vikings to sail to Greenland and establish colonies.A few centuries later, a cooler period called the Little IceAge occurred, as shown in Figure 18B.Temperature change (C)Figure 18 The last glacial maximumwas 18,000 years ago whenEarth’s temperature was 6°C coolerthan present.Temperature Changes forLast 18,000 Years3Medieval climatic2 Holoceneoptimum1 maximum0–1–2Little Ice–3Younger- Age–4Dryas–5 18 16 14 12 10 8 6 4 2 0Thousands of yearsSECTION 4 Earth’s Changing Climates 535

Dinosaur ExtinctionThe impact of a largeasteroid 65 million yearsago on Mexico’s Yucatánpeninsula may havecaused the extinctionof dinosaurs and otherspecies. The dust fromsuch an impact wouldhave caused months ofdarkness and drasticallylowered temperatures.Animals like dinosaursthat needed large suppliesof food would havesuffered most. Researchwhat evidence scientistshave for such an impactand report your findingsto your class.Causes of Climate Change Numerous factors influenceclimate and act on diverse time scales. Over millions of years,factors such as mountain building and continental movementare important. Over years and decades, ocean currents, temperatures,and snow and ice cover play a big role. Climate is the netresult of all factors on all timescales.Variations in the receipt of solar radiation are important ona scale of hundreds to thousands of years. Changes related toEarth’s orbit are the most important factors, producing changesthat determine the rhythmic cycles of glaciation. These includechanges in the tilt of Earth’s axis of rotation, the shape of itsorbit, and the timing of the seasons with respect to distancefrom the Sun. The tilt, for example, is now 23.5°, but has variedbetween 21.5° and 24.5°. These changes alter the amount anddistribution of solar radiation that reaches Earth.Sunspots similarly affect the amount of radiation received byEarth. During one period from 1645 to 1715 sunspot activitywas very low. This period is correlated with long winters andextreme cold temperatures in Western Europe, known as theLittle Ice Age. Sunspots are important on historical time scales.Volcanoes also play a role on this scale. They spew out vastamounts of dust that can block sunlight for years. For example,the eruption of Mt. Tambora in Indonesia in 1815 created thecold weather conditions that gave 1816 the name “The YearWithout a Summer.”The Human FactorHuman activities, such as the burning of fossil fuels, manufacturingprocesses, deforestation, draining of wetlands, and intensiveagriculture, have influenced Earth’s atmosphere significantly. Theseactivities modify the surface heating and the water and carboncycles. They also increase the atmospheric concentrations of tracegases, dust and air pollution.Figure 19 When organisms dieand decay, some carbon is storedas humus in the soil and some isreleased back to the atmosphere ascarbon dioxide.Describe how trees affect levels ofcarbon dioxide and oxygen in theatmosphere.Carbon inOceansCarbon inOrganismsCarbon inAtmosphereCarbon in OrganismsCarbon in SoilFossil FuelBurningDeforestationCarbon in Rock536 CHAPTER 17 Weather and Climate

The Carbon Cycle The carbon cycle, as shown in Figure 19,follows the exchange of carbon among the ocean, land, andatmosphere. Carbon is the basis of all organic matter. The changesin the carbon cycle are particularly important both meteorologicallyand ecologically. The carbon cycle is affected in two ways bydeforestation and loss of vegetation—less carbon dioxide isabsorbed from the atmosphere during photosynthesis, and decayingand burning wood adds carbon dioxide to the atmosphere.CalculateCARBON DIOXIDE (CO 2) CONCENTRATION Concentration of CO 2in the atmosphere hasincreased at a constant rate of about 4.2 percent per decade over at least the last30 years. Assuming this rate remains constant, you can predict its concentrationin the future by using the following formula:CO 2(year 10) CO 2(year) CO 2(year) rate of CO 2increaseIDENTIFYknown values and unknown valuesIdentify the known values:The concentration of CO 2in 2000was 369 ppmRate of CO 2increase between 1990and 2000 was 4.2 percentIdentify the unknown value:What will be the concentration ofcarbon dioxide in 2010?Concentration of CO 2 ? ppmSOLVEthe problemSubstitute the known values into the equation:Concentration in 2010 369 ppm 369 0.042Concentration in 2010 384.5CHECKyour answerMultiply 369 .042 and subtract from 384.5 to get the value in 2000.CO2 Concentration (ppmv)380370360350340330320310 1955Mauna Loa, Hawaii1965 1975 1985 1995 2005Year1. Use the same method to find carbon dioxide concentration in 2020.2. Assuming that conservation efforts reduce the rate of carbon dioxide increase to2.6 percent per decade, predict the concentration in 2010?For more practice problems, go to page 879 and visit Math Practice at 4 Earth’s Changing Climates 537

Trace Gases Today’s atmosphere contains on average about380 ppm of carbon dioxide. This is an increase of 66 ppm, or 21percent, since measurements began in 1957. This level is fargreater still than at the beginning of the nineteenth century,when levels were stable at 280 ppm. Human activities have alsoincreased the concentration of other trace gases—methane bymore than 100 percent, nitrous oxide by about 10 percent. All ofthese gases are important in heating the atmosphere.Figure 20 The concentration ofozone over Antarctic has dramaticallydecreased between 1979 and2003. Concentrations in the holeare about eighty percent lower thanwhat would be there naturally.Explain why scientists are concernedabout decreasing concentrationof ozone in the stratosphere.Oct. 1979Oct. 2003Total Ozone (Dobson Units)150 325Global Warming Global warming is an increase in the averageglobal temperature of Earth. Global temperatures haveincreased over the last century by about 1°C. This may seemsmall, but the entire global temperature increase since the lastice age is only 6°C. Our understanding of global warming isincomplete, but evidence strongly suggests that the increase intrace gases is an important component.The Ozone Hole As early as the 1970s, scientists were concernedthat synthetic chemical compounds could destroyatmospheric ozone. They worried about exhaust from supersonicaircraft and chlorine and fluorine compounds, such as theCFCs (chlorofluorocarbons) used in refrigeration, aerosolsprays, and other processes. Since ultraviolet radiation breaksdown DNA, less protection from solar ultraviolet radiationpotentially could affect the quality of life on Earth. In 1985,British scientists found a hole in the ozone layer over Antarctica.The change in the ozone layer between 1979 and 2003 isshown in Figure 20. When study of the air in this hole showedthat it was largely man-made, an international agreement wasmade to limit the use of CFCs. Recent studies indicate that actionstaken as a result of the agreement are having an effect on levels ofchlorine in the atmosphere, which are decreasing each year.The Land Surface Humans change the land surface bydraining swamps, plowing fields, and building cities. Extensivestudies have suggested that these processes might affect local orregional climate, but the issue is still controversial. The climateof cities is different than the climate of the surrounding countryside.Effects on larger scales are not as clear.One concern is desertification. Desertification is the endproduct of many types of changes that make once-productiveland unusable. Human activities such as overgrazingof livestock, deforestation, and irrigation of cropsmay contribute to the process of desertification insome areas of the world.500538 CHAPTER 17 Weather and Climate

El Niño and La NiñaEl Niño is a climatic event that involves the atmosphere andoceans. Normally, the trade winds blow warm surface waterwestward toward a low pressure area in the western Pacific. Thewarm surface water is replaced by cold, nutrient-rich water thatis upwelled from below the surface. When the tradewindsweaken, surface pressure patterns break down and the flow ofwarm water is reversed. Nutrient-rich cold water is no longerupwelled and warm, nutrient-poor water remains at the surface.Fewer fish and other marine life can be supported by thenutrient-poor water. Rainfall in the western Pacific decreases,where as heavy rain and flooding can occur on the normally drycoast of Peru. El Niño can dramatically alter global weather patterns.For example, a strong El Niño can lead to flooding andmudslides in California, as shown in Figure 21, and droughts inIndia, Australia, and parts of Africa.The opposite of El Niño is La Niña, which occurs whentradewinds in the Pacific are unusually strong and equatorialoceanic surface temperatures are colder than normal. La Niñacan cause drought in the southern United States and excess rainfallin the northwest.Figure 21 Parts of the PacificCoast Highway in California havebeen disrupted by erosion andmudslides caused by El Niño.SummarySeasonal•ChangesThe tilt of Earth’s axis changes the amount ofsolar radiation received by the northern andsouthern hemispheres throughout the year,causing the seasons.•Long-term Climate ChangesCycles of glaciation occur on the scale of tens•of thousands of years.Sunspots and volcanoes influence climate onshorter timescales.•The Human FactorHuman activities have increased theconcentration of trace gases and decreasedstratospheric ozone.•El Niño and La NiñaEl Niño is a warming of the Pacific Ocean withworldwide effects. La Niña is the opposite ofEl Niño.Self Check1. Identify ways that humans may be affecting climate.2. Explain why the contrast between land and waterchanges with the seasons.3. Explain why it is difficult to identify any single cause ofan observed climate change.4. Think Critically What can be done to stop globalwarming? What can you do to help?5. Use Percentages The eruption of Mount Pinatubo in1991 put large amounts of dust into the atmosphere.Scientists say this decreased the average global temperatureabout 0.8 percent during the next year. Howwould this affect an area with an average temperatureof 25°C before the eruption?6. Calculate Areas of the southeastern United States mayreceive 15 percent of their rain during hurricanes. Ifaverage rainfall for this area ranges from 100–200 cm,how much of this might be from hurricanes?More Section Review gpescience.comSECTION 4 Earth’s Changing Climates 539APF/Getty Images

Design Your OwnInvestigating MicroclimateGoals■ Investigate how environmentalvariablesrespond to variousmicroclimates.Possible Materialsdirectional compassthermometerrain gaugemeter sticksmall plastic cups*graduated cylinder*Alternate materialsSafety PrecautionsReal World ProblemWhile we can talk about global climate or regional climate, we alsocan discuss climate on the scale of a few meters. We call climate atthis scale a microclimate. For example, because cold, heavy air drainsdownhill, valley fog sometimes forms in moist, low-lying areas.Along the California coast, coastal fog collects on the needles ofredwood trees, drips to the ground, and is absorbed by the tree’sshallow root system. This microclimate helps the coastal redwoodssurvive, nestled in the fog belt along the California coast. In this lab,you will investigate local differences in microclimate.Form a HypothesisChoose an aspect of climate, such as precipitation, light, or temperature.Form a hypothesis to explain how this aspect influences localenvironments. Predict how these factors will vary in response to differencesin your microclimate variable.540 CHAPTER 17 Weather and ClimateBill Ross/CORBIS

Test Your HypothesisMake a Plan1. Decide what microclimate factor you will investigate, and what environmentalfactor you will monitor for effects.2. How will you measure the selected microclimate variable? Whatequipment will you need? How often will you make measurements?3. Choose sites for making measurements. Will these sites vary in microclimate?Is the environmental variable you chose present in these places?4. Decide how you will measure your environmental variable. What equipmentwill you need? How often will you make measurements? Should the microclimatemeasurement happen at the same time?5. Prepare a data table to record your measurements. Will you record the time of themeasurements? Should you record the weather at the time of measurements?6. Before you begin, list the steps of your procedure. Include all materials needed foreach step. Does your procedure give you the data necessary to test your hypothesis?Follow Your Plan1. Be sure that your teacher approves your plan before you start.2. Carry out your experiment as planned. Be sure to record all data in the appropriateplaces. Follow all appropriate safety precautions.3. Record all observations and data in your Science Journal.Analyze Your Data1. Make a graph of your data. Put the microclimate variable on the y-axis, andthe environmental variable on the x-axis.2. Discuss any trends you see in the data based on your graph.3. Infer any effects that the weather had on microclimate variables. How did thisaffect your environmental variable?Conclude and Apply1. Discuss your predicted environmental responseto microclimate. Did your results support yourhypothesis?2. Predict how changes in global climate wouldaffect the microclimate and response variablesthat you studied.Compare your results with the data ofother students who measured the samemicroclimate variable. Present thecombined data to the class. For more help,refer to the Science Skills Handbook.LAB 541Philippe Colombi/Getty Images

The Grapes of Wrathby John SteinbeckIn The Grapes ofWrath, Steinbeck tellsthe story of the fictionalJoad family, who lived inOklahoma in the 1930s.Like thousands of familiesliving in the droughtstrickendust bowl of thecentral United States, theJoads were tenant farmers who lost their farm. Suchfamilies piled their belongings into rickety trucks andmigrated to California seeking work as fruit pickers.Although the drought alone caused muchhardship, it was gigantic dust storms that finallydestroyed their crops. Steinbeck describes such astorm in the following words:“The wind grew stronger, whisked understones, carried up straws and old leaves, and evenlittle clods, marking its course as it sailed acrossthe fields. The air and the sky darkened andthrough them the sun shone redly, and there was araw sting in the air. During a night the windraced faster over the land, dug cunningly amongthe rootlets of the corn, and the corn fought thewind with its weakened leaves until the roots werefreed by the prying wind and then each stalk settledwearily sideways toward the earth andpointed the direction of the wind.”When the storm finally ended, the buildings,fences, and trees were blanketed with thick layers ofdust—a grim reminder of how the Joads’ lives hadbeen changed forever.UnderstandingLiteratureHistorical Novels Authors often use historicalevents as inspiration. When a pieceof fiction combines historical events orcharacters with fictional plot and dialogue,it becomes a historical novel. Well-writtenhistoricalfiction can aid the reader inunderstanding how people actually experiencedan important time in history.Respond to the Reading1. How does the dust storm affect thecrops?2. What might cause such a dust storm?3. Linking Science and Reading Write aparagraph describing the effects of ahurricane or tornado.The dust bowlresulted from interactionsbetween natural elements, such asclimate, plants, and soil, and human elements,such as farming practices and economics.When the dust bowl occurred, vegetation wasalready sparse. This reduced friction andallowed the wind to gain speed.With no moistureto bind soil particles together, the soileroded.Dust from these storms was carried upto 3,000 km away from its original source.Thedust storms were a type of squall that sometimesbring rain to these semi-arid plains.542 CHAPTER 17 Weather and ClimateAP/Wide World Photos

Earth’s Atmosphere1. Earth’s atmosphere is 78 percent nitrogen,21 percent oxygen, one percent argon, andincludes small amounts of trace gases.2. The stratosphere is the upper layer of theatmosphere where temperature alwaysincreases with height. The troposphere isthe lower layer where most weatheroccurs.3. The troposphere is heated primarily byEarth’s surface after it absorbs radiationfrom the Sun.4. Land absorbs and emits heat efficiently, butwater resists temperature change.5. Clouds form when warm air carryingwater vapor rises until it is cool enoughto condense.Weather1. Major pressure beltsand wind belts arecaused by unequalheating between theequator and the polesand modificationsresulting from Earth’srotation.2. Specific weather patterns are associatedwith high and low pressure cells.3. Air masses are large blocks of air with similarproperties of moisture and temperaturethroughout. They interact in zones calledweather fronts.4. Severe weather includes thunderstorms,downbursts, tornadoes, and hurricanes.LHHLLHLHHHLLHHLClimate1. Climate refers to the mean weather conditionsand their annual variations in an area.2. Climate is part of an Earth system thatincludes the atmosphere, biosphere,hydrosphere, cryosphere, and lithosphere.3. Latitude is the most important factor indetermining climate.4. Continents, mountains, and oceans influenceclimate on a large scale, and smallscalevariations are termed microclimates.Earth’s Changing Climates1. Long-term changes include cycles ofglaciation. Causes of climate change includechanges in Earth’s orbit, solar activity, volcanism,and human intervention.2. Global warming has been documented. Thereasons for it are complex and not fullyunderstood.3. Increased concentrationsof trace gases and damageto the ozone layer areprobably caused byhuman activities.4. El Niño and La Niñaaffect ocean currents andcoastal winds, causingserious droughts andflooding in some areas.Use the Foldable that you made at the beginningof this chapter to review what you have learned aboutweather and climate.Interactive Tutor gpescience.comCHAPTER STUDY GUIDE 543

iosphere p. 529continental climate p. 532El Niño p. 539global warming p. 538greenhouse effect p. 520jet stream p. 525La Niña p. 539latent heat p. 520lee rain shadow p. 533maritime climate p. 532sea breeze p. 533subtropical high p. 525temperature inversionp. 519troposphere p. 519weather front p. 526westerlies p. 524Match the correct vocabulary word(s) with eachdefinition given below.1. area of interaction between air masses2. climate with a strong ocean influence3. energy used to evaporate water4. layer of the atmosphere where mostweather occurs5. global weather event(s) that involveoceans and the atmosphere6. most important of three major wind belts7. fast, powerful air current that affects manyweather processes8. area of reduced precipitation on one sideof a mountain range9. a region of very stable air that resists risingneeded to form clouds and dispel pollution10. warming of the atmosphere involving heatabsorption by trace gasesChoose the word or phrase that best answers thequestion.11. Which has great ranges in temperatureand little ocean influence?A) continental climateB) El NiñoC) La NiñaD) maritime climate12. Which is the percent of solar radiationreflected from the surface?A) albedoB) Coriolis effectC) greenhouse effectD) urban heat island13. Which is the most important factor indetermining climate at a given location?A) altitude C) latitudeB) continents D) mountainsUse the illustration below to answer question 14.Windward side14. Which influence on regional climate isshown above?A) continental locationB) lake effectC) lee rain shadowD) maritime location15. Which triggers droplet formation in clouds?A) evaporation C) ozoneB) dust D) thermals16. What type of weather is most closelyassociated with a warm front?A) drizzle or steady rainB) downbursts or windshearC) hurricanes or tornadoesD) thunderstorms17. Which is a trace gas?A) argon C) oxygenB) nitrogen D) ozoneLeeward side18. Which surface reflects solar radiationthe most?A) bare soil C) snow fieldsB) forest D) ocean544 CHAPTER REVIEWVocabulary PuzzleMaker

Interpreting Graphics19. Illustrate Earth’s major pressure beltsand wind belts, with labels showing thewesterlies and the trade winds.20. Make a table comparing characteristics ofcontinental and maritime climates.Use the data in the following table to answerquestion 21.City TemperaturesCities at Average July Average JanuaryDegrees N Temperature TemperatureLatitude (°C) (°C)72 20 4541 21 945 29 240 31 1021. Identify Based on the data in the table above,identify the latitudes of the cities thathave maritime and continental climates.Use the illustration below to answer question 26.ColdDaySea breezeWarmWarmNightLand breezeCold26. Explain why a sea breeze blows toward theland in the afternoon, and a land breezeblows toward the water in the evening.27. Infer how global warming might increasethe frequency of severe weather, such ashurricanes.28. Describe the carbon cycle and explain howhuman activities might interfere with it.29. Explain how water droplets form in cloudsand the conditions needed to make themfall as some form of precipitation.30. Identify some of the ways that human activitieshave interfered with the water cycle anddescribe some results of these activities.31. Explain how El Niño affects global weatherpatterns.22. Explain why the continental United States isprone to severe weather, such as tornadoesand hurricanes.23. Infer why scientists are so concerned aboutfinding a hole in the ozone layer overAntarctica.24. Form a hypothesis about how we might determinewhether human activities haveplayed a role in global warming.25. Identify some ways that plants and animalsmight adapt to changing climate patterns.Hint: Think of how organisms adapt toextreme conditions.More Chapter Review gpescience.com32. Convert Units The high temperature of asummer day in the United States mightbe 81°F. What would this temperaturebe in France where they use Celsiustemperatures? Hint: Use the formula°C (°F 32) 5/9.33. Compare Ratios City A had 175 cloudydays in 2004. In 2004, 56 percentof city B’s days were cloudy. Whichcity had more cloudy days? Show thecalculations you did to find youranswer.CHAPTER REVIEW 545

Record your answers on the answer sheet provided by your teacher or on a sheet of paper.1. Which makes up most of Earth’s atmosphere?A. carbon dioxideB. carbon monoxideC. nitrogenD. oxygenUse the figure below to answer question 2.CO 2 Concentration(ppm)3603503403302. Which is used by photosynthetic organismsto produce almost all of Earth’s atmosphericoxygen?A. carbon monoxideB. carbon dioxideC. methaneD. nitrogen3. Which accumulated in the stratosphereover millions of years and shielded Earthfrom ultraviolet rays from the Sun?A. argonB. nitrogenC. oxygenD. ozoneComparison of CO 2 Concentration toTime of Year and Latitude1982 1983 1984-90S090NLatitude4. Which type of air mass would most likelybe moist and warm?A. continental polarB. continental tropicalC. maritime polarD. maritime tropical5. Which is a series of windy gusts formedwhen a downdraft hits Earth’s surface withparticularly strong force?A. hailB. squallC. thunderstormD. tornadoUse the diagram below to answer question 6.Sun6. Which is caused by absorption of longwavelength radiation by trace gases?A. condensationB. greenhouse effectC. latent heatD. precipitation546 STANDARDIZED TEST PRACTICE

Use the table below to answer question 7.7. Over which surface is the least amount ofsolar radiation absorbed?A. bare soilB. dense forestC. desertD. snow8. Which are fast, powerful flows of windimbedded in global wind systems?A. jet streamsB. sea breezesC. subtropical highsD. westerliesLand SurfaceAlbedoBare soil 25Snow 90Desert 50Dense forest 1010. Describe the major differences betweenthe conditions that existed 18,000 yearsago from the conditions of the present.Include descriptions of the climatic, geological,and biological conditions.11. Explain how the stratospheric ozone layeris formed. Also explain its importance inregard to the quality of life on Earth.12. What causes uneven patterns of heatingon Earth’s surface?13. Which factors cause climate?Use diagram below to answer question 14.Warm air9. If the average concentration of carbon dioxidein Earth’s atmosphere at the beginningof the nineteenth century was 280 ppm andit presently is 380 ppm, what percentage oftoday’s concentration existed at the beginningof the nineteenth century?Review Never leave any answer blank.Cold air14. PART A What are weather fronts?PART B How do air masses interact at acold front?Standardized Test Practice gpescience.comSTANDARDIZED TEST PRACTICE 547

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