Human Act雪vity and CI冒mate Change

ln this activity, Students w川examine g「aphs of GHG emissions

and their inc「eases associated with human activity。 They wi=

focus on C膿,亡Hヰ,畦凸, CFCs, and寄書。 Students wi!l calcu!ate

SOme Pe「SOnal contributions to C凸2 emissions.

Background

Most scientists beiieve that human activity is aite「ing the

COmPOSition of the atmosphere by inc「easing the concent「ation of

greenhouse gases (GHGs). G「eenhouse gases occu「 natu「al寡y in

the atmosphe「e and their p「esence resu!ts in what atmospheric

SCientists cai! the greenhouse e冊∋C宣。案t is important to remembe「

tha=he greenhouse e情ect is what keeps the earth warm enough

to be habitab!e。丁he cu「rent concem is directed at an enhanced

greenhouse e惟∋Ct, One that wou!d put more heat萱absorbing gases

into the atmosphere, the「eby inc「eas!ng g!oba! temperatures。 The

enhanced greenhouse e惟融has been linked to inc「e挙ed GHG

emissions from human activ軸es.

Nit「ogen (78%) and oxygen (21 %) constitute 99% of the dry

atmosphere. The rest of the gases, inc案uding GHGs, are

CO!iectively class師ed as ’ltrace’’gases due to their Iow

COnCent「ations 。

丁he recent attention g!Ven tO the g「eenhouse effect and global

Warm!ng is based on the reco「ded increases in concentrations of

SOme Of the g「eenhouse gases due to human activity。 Of

Pa面cular interest a「e wate「 vapor, Carbon dioxide, methane,

nitrous oxide, Chloro皿o「oca「bons, and ozone, With the exception

Of chlorofluoroca「bons, al! of these gases occur natura11y and are

also p「oduced by human activity.

WAtervapo「 is the most impo正ant GHG on the planet. Unlike

most of the other atmosphe「ic gases, Water VaPOr is conside「ed to

be a ’va「iab!e’gas; that is, the percentage ofwater vapor in the

atmosphe「e can va「y g「eatly depending on the Iocation and

SOurCe Of the air. Fo「 example, OVer the tropicaI oceans, Wate「

VaPO「 may aCCOunt fo「 4% of the tota! voiume of gases, While over

deserts or at high altitudes言t may be nearly absent。 Water vapo「

abso「bs heat readi書y, When discuss!ng gObal wa「mlng, however,

PeOPIe o債en don’t conside「 wate「 vapo「。 Why not? The main

reason is that human activity is not di「ectly changing water vapo「

COntent. However, We do di「ect!y in皿ence other GHGs。 Although

Other GHGs are individual!y Iess impo巾ant than water vapor,

increasing their concentrations may a惟∋Ct gIoba! cIimate in

Significant and measurab書e ways.

Carbon dioxide (CO2) is considered the most important human-

influenced GHG。 Scientific measu「ements reveal an unmistakable

g!oba=nc「ease that is rapid and escalating, This increase arises

Primarily from the buming of fossil fuels (motorized vehicies,e!ectric power plants, and homes heated with gas or oii) and the

bumtng and c!earlng Of forested land fo「 agricu!tural purposes.

Methane (亡H4) is la「ge!y a product of natu「ai bioIogic processes,

but its output can be acce!erated by human activities. CH4 is

emitted f「om the decay of organic matter in waterlogged soils (for

example, Wetlands and rice paddies) and f「om the digestive t「acts

Of grazing animals (for examp!e’rurTinants)"丁he additions f「om

human activities inc!ude the expans!On Of 「ice agriculture, the

lnCreaSed number of livestock, the increased number of land剛s;

and leakage from natu「al gas pipelines。

ChIorof寒uorocarbons (CFCs) have no natural source; they a「e

P「Oduced entirely by human activity. CFCs have histo「ica=y been

used wide!y as ref「ige「ants in ai「 cond曲oners, refrige「ators,

freezers, and heat pumps。丁hey are found in some foam p!astics

and used in some electronics manufacturing. Even though CFC

PrOduction has been vastly reduced, these compounds remain in

the atmosphere fo「 a Iong time; We Shall see their e情ects as

GHGs for many yea「s。

Nitrous oxide (畦口) is a natu「a!Iy occur「ing GHG, Which has

increased significantly in recent years due to human activity.畦口

is em批ed from coa!-bumlng POWe「 P!ants and can be re!eased

from the breakdown of chemicai fe出Iize「s in the so旺

Ozone (Og) is also a greenhouse gas. It is impo巾ant not to

COnfuse the p「esence of the ozone in the stratosphe「e (a good

thing) with the p「esence of ozone in the t「oposphere (a bad thing)"

in the troposphere, OZOne Can be a maJOr COmPOnent Of u「ban

SmOg - damag書ng CrOPS and agg「avating respiratory problems as

Wel書as enhancing the greenhouse effect。

The concent「ations of these GHG are increasing (although事

thanks to recent g!oba! ag「eements, CFCs are being Ia「ge寒y

eliminated and their concentrations have begun to drop in the

lowe「 atmosphe「e). The emissions are not uniformly distributed

global!y, Most of the emissions come f「om the mo「e deve!oped

COuntries, Where power gene「ation, POWe「 COnSumPtion, and

living standards are highest。

!n this activity, Students wi= examine graphs of GHG emissions

and thei「 increases associated with human activi[y,丁hey wi=

focus on Cロ王, CH4,畦口, CFCs, and口雪. Students wil菓calcu漢ate

SOme Pe「SOna! cont「ibutions to C口重emissions.

Leaming Goa8s

I Studentswi11 be ab!e to ident申y sources ofthe m争jor

greenhouse gases and identfty the curren=「ends in

atmosphe「ic concent「ations.

2　Students wiii be able to calcu!ate g「eenhouse gas emissions

On Pe「SOnal and large「 sca!es。

Materials

・ Graphs and charts ofgreenhouse gases and human activity

. Citymap

.　Calcu音ato「

Procedu「e

l B「ainsto「m possibIe human sou「ces ofGHGs。 Whe「e do

these gases come from? Are the sou「ces common all over

the wo「ld or a「e some a「eas large「 sources than othe「s?

2　Read and discuss the charts and graphs。 How does the

information support o「 contradict the ideas formed during the

b「ainsto「mlng SeSSion?

3　Compare the GHG g「aphs with othe「 graphs (fo「 examp!e,

globai tempe「atu「e and human popu!ation inc「eases) during

the same time span。 Come up with you「 OWn COmParisons.

What kinds of trends do you predict? Can seemingIy upwardtrends be reversed?

4　Discuss global emissions ofGHGs, Fo「 example, the United

States has only a sma書l pe「centage of the wor!d’s population

but emits a disp「opo舶onate share ofthe global C軸, China

has a poputation of over a b輔on peop!e。 What would

happen if China ”deve!oped’’to the point where most fami!ies

OWned an automobiIe that emitted言寄2?

5　CaIcu!ate the persona!伯mily/c!ass contribution of C口重due

to vehic!e use:

・ Using a city map (if necessary), eStimate the distance

f「om you「 home to schoo=n mi!es。

・ ldent申y the type offami!y vehic!e used based on the

types Iisted in the tab!e below.

・ Calcu!ate the amount ofgas used weekIy ifyou rode to

and from school everyday in a private car「o do this:

・ Add up the tota! numberofmilesfor lO round trips

to schoo! (「emember, eaCh time you are d「opped

O情at school, the d「iver has to d「ive home, SO there

are 2 「Ound t「ips a day)

・ Divide thetota! bythe mi!es pergallon to

dete「mine the gallons of gas bumed

・ Mu!tiptytheC龍「eleased pergal!on

・ Examp!e: lfyou !ive 4 mi!esf「om school, yOu「Ca「

trave!s 16 miIes per day to drop you offand pick

you up, O「 80 miles perweek. Atthat mi!eage, a

full-Size ca「wi!! bum 5 gaIIons of gas per week.

Five gai!ons of gas wi!! produce lOO pounds of

書跡eVery Week.

・ Calculate the ciass [otal as ifeveryone rode to schoo=n

a private vehic!e。

・　Students who rideをhe bus: do the same ca看cuIations

aga町uSing the figu「es fo「 the bus and dividing the

total亡0王re案eased by the app「OXimate number of

Students that ride on the bus,

・ Determine how many students walk o「 bike to school。

丁hey do not cont「ibute additiona! C口重tO get tO and f「om

SCh○○1。

. Now 「e-Ca!culate the class totaI based on the type of

transportation actua=y used by students。 Compare the

resuIts。 How much diffe「ence is there?

*Buses add more CO璽Pe「 ga!lon, but they carry more passenge「s, SO be sure to

COnSider contribution by passenge「, nOt just vehicle.

Assessment

The dispa「ity between population size and GHG emissions is

!arge, but very d珊cult to address without altering the IifestyIe of

the highest GHG emitters, at least in the sho巾te「m"

As a written assignment, Pick one source of言出e emission

COmmOn in the U,S. and a「gue in support ofa 50% reduction in

鷺O± emissions f「om that source。 「もdo so, they must explain二

・　Thesources

・ Howthey propose to achieve the reduction

・ The impact ofthe 「eduction on American lifestyIes and/o「

eCOnOmy

・ Howthe reduction mights!owthe build-uP OfGHGs

看magine that you live in a developing country. Argue that you

Shou!d be a!書owed to continue to inc「ease GHG emissions as you

Pu「Sue a bette「 mate「ial standard of living fo「 thei「 citizens.