放ち4α脇ice age

gIobaI warming一一greenhouse effect

励め-殺傷勿◆ Desc「ibe how the Earth′s climate

has changed over time.

◆ Summa「ize the d碓e「ent theories

that a請empt to exp!ain why the

Earth’s climate has changed.

◆ Explain the greenhouse effect

and its role in g!obal warming.

軸閥聡鰯Duwhg the hstg厄`細l

peIめd w繍訪ended IqOOO

咋OIS `町の脇e G鳩Ot L口々es鵬鳩

cove鳩d dy an enomous闘ock

Ofke t厄t胴s J.5知高向h.

軸翻馨eS弛ぐ情調ate

As you know‖皿e wea血er

constantly changes-SOme一

血nes several也mes in one

day. Saturday your mom-

ing baseball game was

CanCeled because of rain,

but by that aftemoon the

Sun WaS Shi血ng. Now think

about the dimate where

you live. Ybサ　Probably

haven’t no也ced a change血

Climate, because climates

Change sIowly. What causes

dimates to change? Un劇recently climatic changes vere con-

nected only to natural cause§・ However, Studies血dicate血at

human activ咄es may have an in飢IenCe On Clima瞳C Change.

In血is section, yOu W田Ieam how na串al and hunan factors

may in組uence clima屯c change.

酷㊧塾頭㊥溺

The geologic record indicates that the Ear血’s climate has

been much colder血an it is today. In fact, muCh of the

Ear血was covered by sheets of ice during certain periods. An

ice age is a period during which ice collect§ in high lati血des

and moves toward lower la債tudes. Scien慣StS have found evi-

dence of many major ice ages

throughout the Earth’s geoIogic

history. The most recent ice age

began about 2 million years ago.

GIa宙a日Pe誼⑫ds During an ice

age, there are periods of cold and

Periods of warmth. These periods

are called glacial and interglacial

Periods. During少vciaJ pe露o勾皿e

enormous sheets of ice advance,

ge壮ing bigger and covering a larger

area as shown in弼翻総理㊨裏Because

a large amount of ocean water is

紐ozen during glacial periods, Sea

level drops.

C!imate　　　8事

醜聞聡餌Acoo協}gめ納eM紘nko融的eo勅拓e amount

ofso厄r調的めn励e知子納

胎僻i団色s関壷sれeめ拐鳩e妬あ

ofd)OngeS血鵬虞肋七〇高庇

e詰謹露盤筒器f「om a more circular shape to a

more elliptical shape・ When the

orbit is mo「e elliptieaL SummerS

a「e hotter and winters are cooler.

When the orbit is more circula事

the「e is not as much seasonal

Ch ange`

e講書窪t批of the Ea競h′s

axis varies between

21.80 and 24.40.

When the t航is at

24.40, the poles

「eceive mo「e solar

ene 「gy

84　　Chapter 3

輔餅g醸癌腫繭s Watmer慣mes血at occur between gla。al

periods are caued緬e頑ac緬perf砿. During an interglacial

peIiod′ the ice begins to melt and血e sea level rises again・

The last interglacial period began lO′000 years ago and is s甜

occ耽血g. Why do these pe血ods o∝ur? Wi11血e Earth have

another glacial period血血e餌調e? These que§也OnS have

been debated by scientists for the past 200 years.

醐⑪軸髄⑱帥醍醐軸　There are many theo血esわout the

causes of ice ages. Each血eory attemptS tO explain the grad-

ual coo血g血at leads to血e development of enomous ice

sheets that periodically cover large areas Of the E紬批s suト

face. The M紡nko聴力tfeeory explains why an ice age isn’t ju§t

one long cold spe11 but instead altemates between cold and

wam Periods. Milutin Milankovitch′ a恥goslavian scientist’

proposed that changes in血e Earth’s o崩t and in the批of

the Earth′s axis cause ice ages′ aS i皿strated in閥邸肘㊥紬

二二-㊧霊誓霊葦

CircIe every 26′000

years. The ci「cu!ar

motion of the Earth’s

axis dete「mine§ the

time of year that the

Earth is closest to

the sun.

$珊細伽的虹

鱒cw do you触nk the Ear鵬emptical orbit affects

the amo調t Of sol弧掘diation鳳at撚aches伽re糊屯ce?

(簿e p包ge 136ぬめe虎叩柑紳S鵬の

蜘庇割前e垣醐嫡⑱鵬There are many nat調al factors that can

a挿ect global dimate. Catastrophic events′ SuCh as voIcanic

erup宜ons′ Can in組uence climate. VoIcanic e調Ptions send large

amounts of dust, aSh, and・ SmOke血to血e atmosphere. Once

in血e atmosphereI the dust′ SmOke′ and ash particles act as

a shield, blocking out so m田Ch of血e sun’s rays也La剛血e Earth

COOIs.鴫闘e鵜Shows how dust particles丘om a voIcanic e則P-

岨On block the sun.

軸離e駒e鏡⑱舶証s The Earth′s dimate is further in紐uenced by

Plate tectonics and continental dri龍・ One theory proposes瓜at

ice ages occur when血e continents a工e positioned cIoser to

the polar regions. For example′ apPrOXimately 250 mi皿ion

years ago′ a11 the continents were comected near

the South Pole in one giant landmass ca11ed

Pangaea, a§ Shown in醜聞鴫an During

this缶me, ice covered a large area of

the Ear瓜′s surface. As Pangaea broke

apart/ the con慣nents moved toward

珊e equator, and the ice age ended.

During the last ice age, many large

landmasses were positioned in the

POlar zones. Antarctica/ nOr血em Nor血

Ame血CaI EuropeI and Asia a皿were covered

With large sheets of ice.

醗翻胞墨縄的者的n細erやめnら

sud) aS the one that ocouned at

勅bunt S己#ele/ずらShoIm aboveJ

p畑duGe血ISt納ot青e舶c由

Sun匂旬crs如om at厄危

醜翻聡欝Mud一Of同ngaea一肌e pa刷血ot応now

A妬Sou脇AmeJ細れh的An陶的Ausfro砿

amd Saudi A舶b厄-Was COve鳩d fy con妨)en細l

八℃ Shee鰹.

CIimate　　　85

騒鰭麗揺顕擬態

:5÷鍵≦勺十! 9Qさ≦∑2

The Ride to Sd1001

Find out how much ca「bon

dioxide is released into the

atmosphere each month from

the car or bus that transports

you to schooI"

置。 Figure out the distance

from your home to school.

2置From this figure. caiculate

how many kilometers you

t「ave暮to and from schoo!,

in a ca「 o「 bus, Per mOnth"

3置Divide this number by 20.

This represents approxl-

mateIy how many gallons

Of gas are used during

your trips to schoo!"

4。 1f buming l ga! of gasoline

Produces 9 kg of ca「bon

dioxide′ how much ca「bon

dioxide is released?

86　　　Chapter 3

観㊨鞋劉騎雷論点艶蜜

Is也e Ea競h really experiencing global warming? G言obal

warming is a血se in average global temperatl虹eS血at can res山t

from an血CreaSe血the greenhou§e e縦ct. Tb understand how

glchal waming wo血sI yOu must紐st leam about the green-

house e旗2Ct.

釦㊧㊧節帥0鵬S㊤輔ect The greenhouse effect is血e Ear皿’s

na請ral heat血g process’血Which gases in the atmosphere

trap themal energy. The Earth′s atmosphere perfom§血e same

function as血e glass windows in a car. Think about瓜e car

i皿strated in醗翻聡粥o ItIs a hot summer day and you are

about to get inside the car. Ybu immediately notice血at it feels

ho壮er inside the car也an outside. Then you sit doⅥm and-

OuCh」yOu bum yourself on血e seat・

棚融⑱駒鳴軸e Wor掴　Greenhouse gases allow sunlight to

pass珊ough the atmosphere. It i§ ab§Oめed by血e EarthIs

surface and reradiated as thermal energy. Many scientists

hypothesize血at the rise in gldbal temperatures is due to an

increase of ca血on dioxide, a greenhouse gas′ aS a reSult of

human activity Most evidence indicate§血at血e increase in

carbon dioxide is caused by the buming of fossil fuels that

releases carbon dioxide into the atmosphere.

Another factor that may add to global warming is

deforestation・ De角樽s物かon is the process of clearing

forests, aS Shown in醇聴闘㊧即日In many countries

around the world, forests are being bumed to dear

land for agric血調e. AIl types of bum血g release

CaめOn dioxide into the atmosphere, thereby

increasing皿e greenhouse e能虹. Plan亡s use ca血on

dioxide to make food. As plants are removed from

the Earth, the carbon dioxide that would have been

used by the plants builds up血the amosphere.

G⑱珊Se即胞醐胎S ⑬管観⑱閲馳醐弧g Many scientists 血ink　醗翻聡翻

that if the average global tempera請e con血ues to血Se, SOme bum加g ledsめ血c鳩ased

regions of血e world might experience血ooding. Wbmer tem- 1e融ofct脇on据わin

pera請es could cause the icecaps to melt, raising血e sea level the drmosphe信

and組ooding low-1ying areas, SuCh as the coasts.

Areas血at receive li劇e rainfall, SuCh as deserts, might

receive even less due to increased evaporation. Scien宜StS Pre-

dict that the Midwest, an ag血crul血ral area, COuld experience

Warmer, drier condi債OnS. A change in cli皿ate SuCh as血is

COuld ham crops. But far血er nor血, SuCh as in Canada, Weather

COnditions for farm血g would improve.

配麿弛恩師蟹陛㊥脚部㊥銅

A cfty just received a wa「ning from the Environmental

Protection Agency fo「 exceeding the automobile fueI

emissions standa「ds・書f you we「e the cfty manageL

What suggestions wou書d you make to reduce the

amount of automob‖e emissions?

且ロHow ha§ the Ear血’s climate changed over time? What

might have caused these changes?

盛りExplain how血e greenhouse effect warms the E紬血.

3。 What are two ways that hunan§ COntribute to the increase

in ca血on dioxide levels in血e atmosphere?

4寄鍋凄鳴鼠ng髄軸岳㊥珊S輔酪　How will the warming of批e

Earth a倍ect agriculture in di節erent parts of the world?

780晦a"皿C