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Climate

System

Table of (;ontcncs

What is Climate?............................................................

The Light FromAbove ....................................................

The Global HeatEngine..................................................

Water,WaterEverywhere................................................

The Oceans....................................................................

ClimateBy Computer.....................................................

The Fire And Ice Before..................................................

Warmer Than We'veEverKnown ...................................

The ChallengeAhead......................................................

Reports to the Nation • Winter1991
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Reports to the Nation ° Winter1991
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Reports to the Nation • Winter1991
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Reports to the Nation • Winter1991
Only by comparing

measurements taken

over many years and

decades, can we

sense the shifting _-"

patterns of

climate.

_
Climate

System

HATIS CLIMATE?The summer of 1988 burned a new" fear into

he minds of many Americans. We watched amber waves of

iin in the nation's heartland tum brown and shriveled under the

nless sky, while water levels dropped along the Mississippi River

t temporarily stranded thousands of barges. [] Wildfires in the

western states blazed through millions of forested acres and shrouded

majestic mountains in a veil of smoke. Across the nation, record heat

and drought forced us to wonder: Is Earth's climate changing before

our very eyes?

One extreme summer in the United States can't answer that

question. Our picture of the climate develops slowly as we watch

scores of [] seasons pass. Some winters bring unusual warmth, some

springs are d_'er than normal. Only by comparing measurements

taken over many)'ears and decades, can we sense the shifting patterns

of climate.

Indeed, ff we look at temperature records taken over the last

century, we find the Earth's surface has warmed a significant amount

over that period. But the meaning of the wanning remains unclear.

Long before humans inhabited the planet, Earth experienced major

environmental changes. The dinosaurs roamed a world much warmer

than that of tcxtay. OurCro-Magnon ancestors huddled through an ice

age that sent massive glaciers spreading over North America and

Europe. Such natural shiftsin climate have punctuated _ the different eras in Earth's history, forcing animals and plants either to go

extinct or to adapt to new conditions.

Reports to the Nation • Winter1991
Reports to the Nation ° Winter1991

Climate fluctuations are nothing new to this

world. ['_ Even in our ov,,n lives we experience

a large degree of natural change in the march of

the seasons, which pass from warm to toM and

back again.

Yet we now,' face the prospect of a different kind

of climate change---one substantially brought on

by human actions. Our industry, agriculture and

daily living cause important gases such as carbon

dioxide to accumulate in the thin blanket of air

surrounding the planet. If we do not alter our

course, scientists predict, _vere cort_'quences may

await us in the not-t{×_ distant future.

To fi_ce such critical issues, we kx_k at the

science behind the immensely complex system

called climate--an entity that tics together the

atmosphere, oceans, land surface and the living

kingdoms of plants and animals. If we want to

measure climate, to predict its course, we must

examine the relationships among these various

components, just as a doctor studies the interactions of skeleton and muscles, heart and lungs.

The Lightfrom Above

As we look at our Earth from space, we see a multicolored marble. Clouds and sn_w-coated lands

create patches of cottony white [_ that interweave with the royal blue background of the

oceans. Breaks in the cloud cover reveal the

continents, brown hues with lighter splotches of

color that indicate desert regions.

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The white areas make Earth a bright planet.

About 30 percent of tile sun's radiation reaching

our world gets reflected ilnmediately back into

space. We notice the reflected light when we travel by airplane over a painfi_illy bright [_] field of

cloud tops or when we walk over a snowy

landscape on a sunny day.

The solar energy that doesn't reflect off clouds

and snow is absorbed by the atmosphere and

Earth's surface. As the surface warms, it sends

infrared radiation, or heat, back toward space.

This type of radiation resembles the wamlth we

feel when sitting at a distance from a hot stove

or campfire.

When we calculate what the surface temperature of the planet should be, based on the heat it

radiates to space, we find the whole globe should

be a frozen wasteland, colder than today by about

33 degrees Celsius (60 degrees Fahrenheit) on

average. The force saving us from this frigid fate is

the atmosphere. The layer of air surrounding our

globe contains important gases such as

water vapor and carbon dioxide, which absorb the heat radiated by Earth's surface and

reemit their own heat at much

lower temperatures. We ,say they

The "Greenhouse Effect": Incoming energy from the sun

(at right) penetrates the atmosphere and heats the surface of the Earth. The warmed surface releases heat in

wavelengths that are absorbed by CO_and other gases in the

air. Only a small amount escapes back to space when large amounts of

these contaminants are present: the rest is trapped, leading to awarmer Earth.

"mip" Earth's radiation and call this planetary warming

mechanism the "greenhouse effect."

Looking at other planets, we can see both

stronger and weaker greenhouse effects. Our

nearest neighbor, Venus, has a thick cloak of

carbon dioxide that heats the planet's surface to an

average of 470 degrees C. Mars, with a mean

surface temperature hovering around -60 degrees

C, has a very thin atmosphere that provides little

greenhouse warming.

Aside from gases in the atmosphere, clouds also

play a major climatic role. By reflecting solar

radiation away from Earth, some clouds cool the

planet. But others wam_ the world by trapping

heat near the surface, thereby contributing to

Earth's natural greenhouse effect. For years, we

could not tell whether the wanning or cooling quality of clouds dominated. But

satellite measurements have recently

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Reports to the Nal_on • Winter1991
A Global Heat Engine: solar energy incident on the Earth is continually redistributed by

currents in the ocean and the atmosphere,

Reports Io the Nation ° Winter1991

proved that, all told, clouds exert a powerful

cooling effect on the Earth. In s()me areas, though,

such as the tropics, heavy clouds may markedly

warm the regional climate.

Clouds and greenhouse .gases fit into something

called the global radiation budget, i'_ Just like a

well-constructed economic budget, the radiation

budget must balance itself. Solar energy" reaching

Earth must equal the energy leaving the planet,

otherwise the oceans would eventually boil away

or freeze solid.

Scientists warn that we are currently upsetting

the Earth's radiation balance through activities

such as burning R)ssil fuels and cutting forests.

These actions cause carbon dioxide and other

gases to accumulate in the air and therefore

strengthen Earth's greenhouse effect. We expect

the planet's surface will warm tip until a new

radiation balance emerges.

The Global Heat Engine

While the radiation budget must balance for the

entire Earth, it does not balance at each particular

spot on the globe. For instance, very little solar

energy reaches the white, ice-covered polar regions, especially during the winter months. Our

spinning planet absorbs most solar radiation around

its waistline, in the tropics and the lower latitudes.

Over time, though, energy" absorbed near the

equator spreads to the colder regions of the globe,

carried by winds in the atmosphere and by currents

f- $.;-;. !DL i-,.-,,'..-'.

COLOR PHOTOG,7,:APH
Polar Cell

Near Surface Circulation

Mid-Latitude Cell -

Tropicat Ceil ------

in tile oceans. To scientists, both air and

water act together as

a giant heat engine.

Just like tile old

steam-powered lo- i

comotives, the oceans

and atmosphere are

set in motion as heat

flows fl'om warmer to

cooler regions.

The global heat engine exerts a strong influence over our

daily lives as it tries to equalize temperatures. It pumps energy into the storm fronts that

sweep across the plains and it powers the hurricanes _ that pound the East Coast and Gulf of

Mexico. In the colder seasons, low-pressure and

high-pressure cells jockey fi)r position eve_' few

days, allowing blasts of Arctic air to pass over

the United States while warm winds move

toward the pole.

The restless atmosphere also transports energy

around the globe by shuffling masses of wet and

do; air. Through evaporation, the air over the

warm oceans absorbs water vapor _ and then

travels to colder regions and to the continental

interiors. Here, the water vapor condenses and

falls out of the sky as rain or snow--a process that

releases heat into the atmosphere.

;_ . Atmosphere

Ocean Surface

_rlies

Ocean Cross

Section

Mid-labtude

Wesledies

Trade

Winds

Mid-latitude

Westerlies

Polar Easlerlies

A system of

prevailing currents

in the atmosphere (blue)

and oceans (red) carry heat

from one part of the planet to another

The forces that drive them are provided by incoming solar energy and the spinning motion of the Earth.

In the oceans, salt helps drive the heat engine.

Over some areas, like the arid Mediterranean,

water evaporates from the sea faster than rain or

river discharge can replace it. _ As the sea water

l)ecomes increasingly salt),, it grows denser. In the

North Atlantic, cool air temperatures and excess

salt cause the surface water to sink, creating a current of heaw water that spreads throughout the

world's oceans. By redistributing heat in this

fashion, the oceans act to smcx)th out differences

in temperature and saltiness.

| _ _._. I{ k*'%.,4, "_l ='= I _i

. Reports tO the Nation • Winter1991
4

Water, Water Everywhere

Through rain, hurricanes, anti snowstorms, we

recognize a few roles water plays in the daily

weather and in the climate system But water also

exerts critical but less obvious influences on our

environn_ent. [] Evaporation fronl moist soils

and plants helps to cool the land surface in the

same way that perspiring c( x)ls our txxties in wann

weather. When we have a sunm-ler drought and

the soil dries, temperatures rise because the land

can no longer use evaporation to cool itself.

Through computer models, we see how water

and vegetation are woven together by the climate.

For example, the models tell us what might

happen if we cut and bum much of the Amazon

rain forest and then convert the cleared areas into

farmland and cattle pasture. Evaporation would

dwindle in the Mnazon region, causing the surfhce

to warm and possibly, rainfall to [_] diminish. We

have not yet studied how such changes woukt

thrmten the survival of other trees in tt_s region, but

we know tl_lt photcxsTnfllests requirc,'s

water, along wifl_ carbon .....

dioxide. ...- f/::_- --:E:----:

Our economy depends heavily on the lakes,

reservoirs, and underground aquifers that store

water for drinking and for irrigating the crops we

eat. Climate changes will ahnost certainly affect

these water resources. Some studies indicate that a

lengthening of the warm season will disrupt agriculture in regions like the northern Great Plains,

where substantial soil moisture comes from springtime snow melt. These areas may become more

arid which would place stress on growing crops.

Supplies of drinking water in some places also

face danger from rising sea levels. If the climate

wanns in the future, scientists predict [_ ocean

levels may swell a f(x)t or more by the middle of

the next century. Salt water could potentially

invade coastal aquifers and poison the

freshwater water supplies for cities

like Miami.

Reports to the Nation • Winter1991
Rising ocean levels also threaten to flood lo_ST : !:!_"

lying areas and could create millions of refugees _-_<:-:: _i_

Bangladesh and other countries. Urban ;_;_:: :!_ 17ci_i_:_ ._

like New' Orleans, Bangkok and Venice may be

unable to afford the costs of protecting them- : ._

selves against the surge of high waves ._::_:_:-.

during _ storms. -. -_-

Water vapor

is the most variable

constituent of the atmosphere and

the mare contributor to the greenhouse effect.

the amount present in the air at any time and place is

determined by the cycling of water through the earth system: chiefly

evaporation from the oceans into the air. from whence, in clouds it eventually falls as

ram or snow to wend its way by way of streams and rivers once again to the sea.

Reports to the Nation • Winter1991
,/_c,,//cvtz 5 %( t[_C SC¢t

The Oceans

Climate experts know much less about the oceans

than about the atmosphere. But one fact stands

out: When compared with tile air above, the

(x'eans react like a sluggish beast. While the

atmosphere can adjust in a few days to a wamfing

or cooling in the ocean, it takes the sea surface

months or longer to respond to changes in heat

coming from the atmosphere. People living near

the c()ast appreciate the ocean's sluggishness

because they enjoy relatively warm winters and

cool summers, especially on the western side of

a continent [_ where ocean winds blow onto the

land. We need only compare the winter climates

of Seattle, Washington, with Duluth, Minnesota

to see how the slow transfer of heat from the

ocean exerts a profound climatic effect.

Sea-to-air

Transfer

The temperature pattems of the sea surface also

determine where storms develop and the directions they travel. The Gulf Stream guides the path

of winter gales in the western North Atlantic and

hurricanes over the subtropical _ oceans. Because the (x:ean can only absorb heat sl()wly,

individual storms have ve U little effect on sea

surface temperature.

In recent years, we have learned much about an

important phenomenon called El Niflc_--a climate

pattern that results when the Pacific Ocean teams

up with the global atmosphere to wreak widespread changes in weather. During a particularl,v

strong E1 Niflo in 1983, torrential rains rio(x_ted the

west coast of South America, while India, Indonesia and Australia suffered severe droughts. El

Niflos are highly irregular, but on the average occur

three to five years apart and arc linked to a pattern

of aunospheric pressure c:dlc_t die

Southern Oscillation.

Water

circulates globally through

the oceans as though carried by a huge

conveyor belt. Cotder water in the North Atlantic sinks to

the deep oceanto resurface and be rewarmed in the Indian and North

Pacific oceans Surface currents carry the warmer stream back again through the

Pacific and South Atlantic. The circuit takes almost 1000 years,

Reports to the Nation • Winter1991

Cold and Salty

Deep Current

Warm Shallow

Current

ORiGiNAL ....' _-"-

COLOR PHOTOGRAPM
s l l rfa cc

_-"_'o ctetertllillC tt'l)Cl'C storj_]+,

t, e thel'

During E1 Niflos, the air and sea perform an

intricate dance. The strong trade winds over the

equator grow weak and alk)w warm currents to

flow into the central and eastern Pacific. Along with

the warn1 water, stomps in the atmosphere shift

eastward. While we do not yet completely understand E1 Niflos, we believe these events can alter

conditions around much of the globe. Some

scientists think part of the E1 Niflo-Southern Oscillation cycle helped create the searing drought

across North America in 1988. Through ongoing

research projects, we are learning how to predict

the arrival of El Niflos a year or more betore they

fully develop, [_ which may greatly aid our ability

to forecast general weather patterns several months

in advance.

Climate ByComputer

In some ways, Earth's climate system resembles

the intricate web of a spider. The clou&s, ocean

currents, solar radiation and myriad other elements all weave together in a chaotic and cornplex way to create our climate. In the real world,

we cannot isolate one piece from the rest. So we

create mathematical climate m(xtels in order to

study individual parts and to assess how the

different elements interact. The models also help

us predict future changes in the behavior of the

climate. For example, we can test how" a global

greenhouse wanning might alter rainfall patterns

for a time in the middle of the next century.

Terrain over North America at four increasingly higher spatial (grid) resolutions. Current

climate models use the terrain depicted in upper left. Increased resolutions from upper

left to bottom right, are expected to yield increasingly useful climate predictions in the

years ahead.

In theo_', the models are simple. They treat

both the atmosphere and the oceans as fluids that

obey basic physical laws.

But the models become complex because they

must include many different and interrelated parts

of the climate including the soil, water vapor in the

air, salt in the oceans, and biological systems. They

slice tip the atmosphere and oceans into thousands

of grid boxes and calculate how the weather

changes in each box. The mathematic equations

require so many calculations ['_ that only the

most powerful computers can solve them. Even

on such machines, it can take weeks of expensive

computer time to simulate how rising carbon

dioxide levels might affect climate.

ORiGiN.c:_, ; ,,,\,:<:.

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Reports to the Nation • Winter1991
Reports to the Nation • Winter1991

The models show that temperature could rise

considerably over many areas of the globe if our

activities continue to intensify the earth's greenhouse effect. Yet, we wonder how much to trust

the computer sinmlations. Despite all their complexity, the m(x.lels are not completely accumteand

we -1-1-1mowthey do not do a gc_x.t job of simulating

clouds or the _'eans. _l"file we continually work to

improve the moJets, we c-an still l_tm illLich from the

imperfect versi(gts in use tcxtay.

TheFireandIce Before

Computer models are not the only t(x)l for studying

climate change. We also draw lessons t?om

records of Earth's history that reach back through

the eons.

For the last few hundred years, weather instrument, s in scatterect locations around the globe have

collected infonnation on temperature, rainfall and

other factors. Going back further tree rings can

trace climate changes over many millennia. In the

westem United States, experts have found a living

Bristlecone pine [_] tree that began growing over

4,800 years ago. The oldest known organism alive

on Earth t(x.tay, this tree set its roots centuries

before the ancient Egyptians began building the

Great Pyramid. But even Bristlecone pines cannot

compete with the geologic record. Rocks and

fossils provide a window to times billions (_f years

before today.

From thermometer measurements to the r(×'k

record, these various chronicles of the past not

ORIGINAL PAGE

,.,_,.OR PHOTOGRAP_H

I1
)

only tell us what previous conditions on Earth were

like, they also provide clues about the causes of

climate change.

Looking back through the ages, we see evidence that the planet has passed many times

tim)ugh warm and cold spells. One of the warnlest

known intervals was the Cretace(ms period about

100 million years ago, near the end of the reign of

dinosaurs. With temperatures about 10 degrees C

warmer than today, sea levels swelled because

water was not locked up in major ice sheets near

the poles. The [_ oceans spilled onto the continents and split North America effectively into two

landmasses. We bdieve such warm conditions

resulted in pm'[ from extra carbon dioxide that

accumulated in the atmosphere because of widespread volcanic activi_,.

Atx)ut 100 nfillion yeal,s ago, Earth's clin_tte began

a slow slide toward ccx)ler conditk)rts, cxfln-finating

during the past _vo million yc_rs in a ,series of repeat-

_x_tice ages, when the average surthce temperature

dropped about 5 degrees C below

today's level.

What caused such drastic climate shifts during

the ice ages? While we believe periodic changes

in Earth's orbit triggered the advance and retreat of

the glacial sheets, the planet's greenhouse effect

must also have played an important role. Bubbles

of ice age air preserved in the glacial sheets of

Antarctica and Greenland reveal that the atmospheric concentration of carbon dioxide and

methane dropped significantly during the glacial

times. Such low levels weakened the greenhouse

effect and helped cool the Earth. To explain the

dramatic fluctuations in carbon dioxide levels, we

must turn to the oceans for answers. A reorientation in major currents during the ice ages may have

increased the ocean's abiliD' to absorb carbon

ctioxide from the atmosphere.

The last ice age began to wane about 18,000

years ago, long before modem human civilizations

blossomed. _ However, our recent ancestors

experienced a so-called Little Ice Age, which lasted

from 1400 A.D. to 1850. During this cold phase,

the global climate probably registered

about 1 degree C

At the peak ol lhe last Ice Age, 18,000

years ago, a permanent glacier had reached down

Irorn the North Pole to cover all of Ganada, Greenland, Iceland and

r_,_:_,,,,-',.: PAGE

COLOR PHOTOGRAPH

much of the northern US and Europe. The ice that

overlay present day New York and Chicago was more than half a

mile deep; two miles of ice weighed down on Hudsoffs Bay

Reports to the Nation * Winter1991
colder than now,', with more severe changes in

some places. Norse settlers disappeared from

Greenkmd at that time, presumably because they

could not survive the cold conditions. Though we

don't know why the Little Ice Age developed, v,,e

suspect a decrease in solar radiation or an increase

in volcanic dust may have triggered the cooling.

Warmer Than We've Ever Known

If the climate cycle were to follow its natural

course, in a few thousand yearn the Earth would

start sliding into another ice age. But our activities

threaten to send the climate speeding in another

direction, toward a greenhouse _ warming.

The burning of coal, oil and natural gas and the

destruction of forests have raised the total amount

of atmospheric carbon dioxide by 25 percent since

the beginning of the indusThe temperature of the land and water surface of the Earth, derived from spaceborne

sensors on NOAAweather satellites. Average temperatures for January, measured m

1979, areshown at left, representing midwinter in the NorthernHemisphere, midsum met

in the Southern Above are temperatures for July of the same year, showing opposite

conditions. Temperatures below freezing are green and blue: warmer temperatures are

in red and dark brown

trial revolution. The accumulation of this gas over

the last century alone now adds as much heat to

the climate system as wouM a one-half percent

increase in the sun's energy output.

Carbon dioxide is not the only climaticallyimportant gas accumulating in the atmosphere.

Manufactured chemicals called chlorofluorocarl×)ns now supply about one quarter of current

additions to Earth's greenhouse effect, f_ Used in

refrigerators, air conditi()ners, foam and insulati_m,

these potent greenhouse gases spell double

trouble. Besides w,arming the Earth, they have

also weakened the stratospheric ozone layer_a

protective shield that blocks out damaging ultraviolet radiation from the sun.

Another powerful heat absorber, methane, has more than doubled in

concentration over J----

1880 1900 1920 19 L

Date

Reports to the Nation • Winter1991 _.
(l °}'eC11}_°lt"_C

ilz a_2otbel" ¢lil.cctiO_t, t°t_ar¢t

the last three centuries, in part from increased rice

cultivation and livestock rearing. Methane levels are

currently climbing at the extraordinarily fast rate of

almost one percent per year.

The buildup of these and other gases has already

strengthened Earth's greenhouse effect. I_] But

it may take several decades to feel the wamfing

because atmospheric temperatures will rise significantly only after the oceans of the world have

slowly wamled.

The postponement may seem like an advantage,

in that it gives us more time to prepare. However, the

time lag could lead tLs to underemphasize the importance of the problem while we still have a

chance to avert drastic climate change. In truth, we

have already committed ourselves to some degree

of warming, even if we could instantly halt the

buildup of greenhouse gases in the atmosphere.

Whatever lies ahead, the world is accelerating its

pace toward that unknown end. In the last three

decades, the annual global release of carbon

dioxide has doubled, reflecting a climb in the rote

of fossil fuel burning and deforestation. As human

population and economic activities continue to

grow, carbon dioxide emissions could double

again in the next three decades unless the nations

of the world limit their consumption of fossil fuels.

Such action would benefit society in many

ways. For instance, through energy conservation,

we can personally save substantial atYK)unts of

money and help reduce our nation's dependence

on R)reign f\lels. Therefore, despite our uncertain_'

concerning future clinute enrage, we are already

beginning to take ce_in steps that will slow the

buildup of greenhou_ g:Lses.

Annual and 5-year averaged values of combined land and ocean temperature of the Earth

for lhe period 1880-1989_ expressed as a deviation from the average temperature for

1951-1980 It is now thought lhat global mean temperature will rise an additional

1 degree C by the year 2025 due to enhanced greenhouse warming, and

about 3 degrees C by the end of the next century Surface

temperatures cooled, by comparison, byabout 1degree C

during the coldest years of the Little IceAge.the

last major climatic change, in the

late 171hcentury •

I"

+0.2

0

D

0"1

i..-

,,...

0

e.

E

1960 1980 2000

Reports to the Nation • Winter1991
Carbon dioxide is a natural component ol lhe atmosphere that serves to requlate g

Through activities of man

burning of fossil fuels, ]tion has risen by

about 10% in the last 30 years: the rate of increase has

Each molecule

that is luced will remain in the air for more

than a century

360

1800 1850 1900 1950 2000

Year

Another powerful heat absorber, methane, has more than

doubled in concentration in the atmosphere since the

time of the Industrial Revolution Principal sources are

nalural wetlands, r,ce cultivation, cattle, and landfills

1800 1850 1900 1950 2000

Year

Man made gases that combine chlorine, fluorine, and

carbon (chlorofluorocarbons) have shown the greatest

increase of any of the greenhouse gases They were

never present in the natural atmosphere and are

rising today at a rate of

about 4% per year

450

1960 1970 1980 1990 2000

Year

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0

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The Challenge Ahead

Are \re barrelling d()wn a runaway route toward

climatic catastrophe, or will the fL,ture bring relatively benign changes that will not thivaten society?

The accumulation of greenhouse gases in the

atmosphere will ahnost certainly cause Earth's

suflace temperature to rise. But we do not know

how quickly the planet will v,'aml or how that

warming will affect different rcgkms of the globe.

Answers to such questions will only come

through intensive research into the mysteries ()f

Earth's climate systeln. To this end, scientists flom

around the world are joining together, as they

never have hefore, in an eftort to adcllwss critical

issues. For example, several international p1()iects

are now seeking to improve our understanding of

clouds and the oceans--two factors that will

greatly influence the pace of global warming.

Compared to other Emns of liD, humar_kind has

inhabited the Earth for a short span of time.

Nonetheless, the needs ()f a rapidly growing

population have begun to stress the limits of the

natural system. The nations of the world now face

a great challenge--to anticipate future climate

change and develop a rational pr()gram for protecting the environment. No need could lye more

pressing, no mission of greater import to future

generations.

Reports to lhe Nation * Winter1991

ORIGINAL PAGE

COLOR PHOTOGRAPH,
ORfGi::,L,',: ;_,' ::

COLOR PHO[OGIRAP,-_

Reports to the Nation • Winter1991
Writers and Contributors

Robert Dickinson, University of Arizona and

Richard Monastersky, Science News

with input from

John Eddy, Office for Interdisciplinary Earth Studies,

Kirk Bryan, National Oceanic and Atmospheric

Administration and

Samuel Matthews, National Geographic Society

The Climate System is the first in a series of publications on climate and global change intended for

public education. They are a joint effort of the UCAR

Office for Interdisciplinary Earth Studies and the

NOAA Office of Global Programs for the purpose of

raising the level of public awareness of issues

dealing with global environmental change. The

reports are written by knowledgeable scientists

and science writers on timely subjects and guided

by a scientific Editorial Board. The second in the

series, The Ozone Shield, will appear in early 1991,

with others to be issued about every six months.

Editorial Board

Francis Bretherton, University of Wisconsin

RobertDickinson, University of Arizona

John Eddy,Office for Interdisciplinary Earth Studies

J Michael Hall. National Oceanic and Atmospheric

Administration

Stephen Schneider, National Centerfor Atmospheric

Research

Samuel Matthews, National Geographic Society

Managing Editor

BarbaraAnderson, Office for Interdisciplinary

EarthStudies

Design, Illustration, and Production

InterNetwork, Inc.. Del Mar. CA. Payson R Stevens.

PatrickHowell, LeonardSirota. EricAltson, AllenBorsky

For additional copies contact the UCAR Office for

Interdisciplinary EarthStudies, PO Box 3000

Boulder. Colorado 80307-3000 (303) 497-1682

Image Credits:

All computer graphic illustrations:InterNetwork, Inc,Cover/

Page 1: _;_Payson R. Stevens; Pages 2-3: top four- ©

James A. Sugar: counterclockwise- _-_Robed Bumpas;

NCAR; NOAA National Severe Storm Laboratory: @ Ed

Brown; nexttwo, _ Payson R,Stevens; Page4: © Payson

R Stevens: Pages 6-7: topthree- NASA: from The Home

Planet ,_"Kevin W Kelley: NASA:Page 8: NCAR: Pages

10-11: NCAR: next 3 © Payson R. Stevens; Page 13:

Thomas Bettge, NCAR;Pages14-15: lop three- © Payson

R.Stevens: next two, ,2 Claire Parkinson: _c_Larry Mayo.

USGS: Page 16: Moustafa Chahine, NASA/jPL & Joel

Susskind, NASNGSFC;Pages 18-19: top four-© Naomi

Coval-ApeL. J Jones, University of New Hampshire: ©

James Blank: _, Naomi CovaI-ApeL :r_Payson R Stevens;

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