chapter 3 environmental quality and sustainability textbook

8/11/2019 Chapter 3 Environmental Quality and Sustainability Textbook

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Patterns in environmental

quality and sustainability

Atmosphere andChange

The Atmosphere

The atmosphere is like a thin

film surrounding the earth. If the earth were the size of asoccer ball on a wet field, the atmosphere would be likethe wet layer around it. In fact, the atmosphere is about500 kilometres thick, although half the mass of the atmos-phere is found in the lowest six kilometres and 99% of theatmosphere is contained in the lowest 40 kilometres.

Within the atmosphere there are four distinct layers, de-fined by whether the temperatures are rising or fallingwith altitude (figure 3.1). The layers are:

Thermosphere. The thermosphere is the highest layer

of the atmosphere, extending from about 80 kilometresabove sea level out to the farthest limits of the atmos-phere. The gases in this layer of the atmosphere arevery thin, and the thermosphere makes up only 0.001%

of the mass of the atmosphere.In fact, there is little differencebetween the thermosphereand a vacuum. The gases inthis layer are oxygen, hydro-gen and nitrogen, and theseabsorb ultra-violet radiation

from the sun, heating up to very high temperatures ex-ceeding 200C and sometimes exceeding 1000C.

Mesosphere. The mesosphere is the second highestlayer of the atmosphere, extending between about 50and 80 kilometres above sea level. This is the coldestpart of the atmosphere because there is very little cloud,dust, ozone or water vapour to absorb heat from thesun. The mesopause, which separates the mesospherefrom the thermosphere above it, is always a constant-90C. The mesosphere also has the strongest winds inthe atmosphere, approaching 3,000 kilometres per hour

in places.

Stratosphere. The stratosphere is found below themesosphere in a band from about 20 kilometres to 50

Changes in atmosphere, soils, water, biodiversity and sustainability

Soil and change

Page 116Causes of soil degradation,the environmental andsocio-economicconsequences of thisprocess, together withmanagement strategies.

Water and change

Page 120

Ways water is used at theregional scale, environ-mental and human factorsaffecting patterns andtrends in water scarcity,and factors affecting accessto safe drinking water.

Atmosphere and

change Page 100The causes andenvironmentalconsequences of globalclimate change.

Sustainability and the

environment Page 136The concept ofenvironmentalsustainability, and amanagement strategydesigned to achieveenvironmentalsustainability.

Outline

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C H A P T E R 3

Biodiversity and

change Page 129The concept andimportance of biodiversityin tropical rainforests, andthe causes andconsequences of reducedbiodiversity in this biome.

ToK BoX Page 114

Truth and Global Warming

Environmental quality and sustainability


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3.1 A cross-section of the atmosphere showing the four layers and thetemperatures at each level.

kilometres above sea level. There is a concentration ofozone in the stratosphere, and as ozone absorbs ultra-violet radiation very well, temperatures rise with in-creasing altitude in the stratosphere. In the lower partsof the stratosphere, most of the ultra-violet radiationhas already been absorbed, so temperatures are cooler.The temperature at the top of the stratosphere is a fairlyconstant 0C, but at its lower limit (the tropopause) thetemperature is typically about -50C.

Troposphere. The troposphere is the lowest layer of theatmosphere, and it contains most of the mass of the at-mosphere, as well as most of the dust, water vapourand pollution. It is the layer in which the weather oc-curs, and it behaves quite differently to the other threelayers. Whereas the three upper layers obtain their heatdirectly from solar radiation, the troposphere iswarmed indirectly by reflected heat from the earthssurface and clouds. Temperatures in the tropospherefall by about 6.5C for every 1000 metres rise in altitude,

although this figure varies from place to place. Thetroposphere comprises a mixture of gases, but the mostimportant ones are nitrogen (78%), oxygen (21%), argon(almost 1%), and carbon dioxide (0.003%). Other gasessuch as hydrogen, helium, krypton, methane, neon,ozone and xenon together make up only 0.001% of theatmosphere. The troposphere also contains water va-pour (the gaseous form of water), but the proportion ofwater vapour varies enormously from place to placeand from day to day.

Q U E S T I O N B L O C K 3 A

1. Draw up a table to contrast the characteristics of the fourlayers of the earths atmosphere.

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>> Some Useful DefinitionsGlobal climate change the changes in global patterns of rainfall and temperature, sea level, habitats and the

incidences of droughts, floods and storms, resulting from changes in the Earths atmosphere, believed to be mainly

caused by the enhanced greenhouse effect.

Global scale the world as a whole.

Local scale areas of limited extent.

National scale the area of a country.

Regional scale an area that encompasses several countries sharing some common element (economic, political,

locational).

Soil degradation a severe reduction in the quality of soils. The term includes soil erosion, salinisation and soil

exhaustion (loss of fertility).

Water scarcity occurs in two forms: physical water scarcity, where water resource development is approaching

or has exceeded unsustainable levels (this relates water availability to water demand and implies that arid areas

are not necessarily water scarce); and economic water scarcity, where water is available locally but is not accessi-

ble for human, institutional or financial capital reasons.

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The Global Heat Budget and Atmospheric

Circulation

All the processes of the atmosphere (and indeed all life onearth) depend on energy from the sun. The suns energyis enormous. The surface area of the sun is 65 million bil-lion square metres, and the energy sent from each square

metre is enough to power one million light globes. Asmall part of the energy produced by the sun reaches theearth. The incoming solar radiation, known is insolation,arrives in the form of short-wave radiation. Short-waveradiationfrom the sun is mainly visible light towards thepurple end of the spectrum with a wavelength of 0.39 to0.76 !m (micrometres, or microns). The reason that thesuns energy is short-wave radiation is that the sun is sohot 5300C. Cooler bodies such as the moon and theearth, emit long-wave radiation, which is mainly infra-red heat with a wavelength of about 4 to 30 !m.

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E A R T H

S P A C E

3.2 The ways insolation is dispersed in the earths atmosphere.

When the suns energy reaches the atmosphere, it is dis-persed in different ways (figure 3.2). Although cloudscover about half of the earth at any time, they are poorabsorbers of the suns energy. Much more solar energy isabsorbed by dust and gases in the atmosphere, especiallywater vapour. Altogether, 19% of incoming solar radia-tion is absorbed in the atmosphere.

The earths surface absorbs 47% of the insolation, somedirectly and some after being reflected or scattered by theatmosphere. A small amount of radiation is reflected by

the earths surface back into space. The amount of energyreflected from a particular place depends on the kind ofsurface on the earth at that point. Light, shiny surfaces,such as snow and ice, have much higher reflectivity (oralbedo) than darker, duller surfaces, such as dark soil or agreen forest (figure 3.3).

3.3 Water has a high albedo (over 90%) if the suns angle is low, butthis falls to less than 5% under a noon sun or if the water is choppy.This early morning oblique aerial view of Myanmars Irrawaddy Deltashows a high albedo from the sea and the rice padis, but high absorptionin the clouds.

The amount of heat received at the earths surface variesaccording to latitude (figure 3.4). Less solar energy is ab-sorbed by the ground in polar areas than equatorial areasfor three reasons. First, the suns rays strike the earthssurface at a lower angle near the poles. Therefore anequivalent amount of solar energy approaching the equa-tor and the poles must be spread over a larger area inpolar areas, meaning that there is less heat per squaremetre on the surface.

The second reason that the poles receive less solar radia-

tion is that the suns rays must penetrate a greater thick-ness of atmosphere near the poles than near the equator.This is because the rays penetrate the atmosphere at anoblique angle. As a result of this, the dust and gases of the

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atmosphere absorb more heat and light, and less reachesthe earths surface.

The third reason that the earths surface at the polesabsorbs less solar radiation is that more of the light thatdoes reach the surface is reflected back into space. Theshiny white ice and snow of the poles has a much higheralbedo than the water and vegetation of the equatorialzones. In fact, snow and ice reflect about 80% of the solarenergy whereas grass and trees will absorb between 65%and 85% of solar energy. Furthermore, any surfacebecomes shinier when light hits it at a low angle evena black bitumen road seems shiny when viewed at a lowangle. The light that reaches the polar surfaces does so ata very low angle, and therefore much of it is reflectedrather than absorbed.

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Cross - sectional areas of sunsrays striking the earths surface

3.4 The intensity of solar radiation depends on the angle which thesuns rays meet the earths surface. The angle of the suns rays (a, band c) and the thickness of atmosphere through which they must pass(d1, d2 and d3) depends on the latitude. At high latitudes, the sameamount of insolation is spread out over a larger area, making the heatless intense.

When radiation is reflected from the earths surface, thewavelength becomes longer, which means that the radia-tion shifts towards the red and infra-red end of the spec-trum. In other words, less of the radiation is in the form

of light, and more of it is in the form of heat. This is sig-nificant because the gases of the atmosphere are relativelygood absorbers of long-wave radiation and thus absorb

the energy emitted by the Earths surface to a greaterextent than they absorb the short-wave radiation comingfrom the sun.

If we examine the amount of energy received and lost atdifferent latitudes over an entire year, the pattern shownin figure 3.5 emerges. The graph shows the average an-nual insolation at each latitude (curve I) and the averageannual loss of long-wave energy (curve II). Although thetotal incoming energy (curve I) equals the total outgoingenergy (curve II), there is a net surplus of energy betweenthe equator and latitudes 38 North and South, while lati-tudes between 38 North and South and the poles have anet deficit.

Latitude

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3.5 The earths heat budget. Average annual insolation at each lati-tude is shown by curve I, while average annual loss of long-wave en-ergy is shown by curve II. Latitudes between the equator and 38 Nand S have a net surplus of energy, while latitudes between 38 N andS and the poles have a net deficit. Note that the horizontal axis hasbeen scaled in proportion to area.

We know that over the history of the planet, the equato-rial regions have not continued to heat up while the polarareas have not kept getting colder. The reason for this isthat a complex mechanism of atmospheric circulation re-distributes heat from the equatorial regions (low lati-

tudes) to the polar regions (high latitudes). It is this redis-tribution of heat energy that creates the worlds pressuresystems and winds.

Of all the solar energy received by the earth, 34% isreflected back into space, either from the earths surface(2%), from the atmosphere itself (7%) or from clouds(25%). However, before the energy is reflected back intospace, some of it is retained in the atmosphere for a while,and this is the heat that provides the warmth that makesthe earth habitable by humans. This process where theinput of heat into the atmosphere equals the output while

an amount is retained for a while is known as the green-house effect, because it is the same principle by which agreenhouse provides a warm environment for crops to

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grow (figure 3.6). Without the greenhouse effect, the earthwould be 33C cooler than it is now. (Note that when werefer to actual temperatures, we use the format 33C, butwhen we discuss differences between two temperatureswe use the format 33C).

Q U E S T I O N B L O C K 3 B

1. With reference to figure 3.2, state theproportion of insolation which (a) isabsorbed by the earths surface, (b) isabsorbed by the atmosphere, and (c) is

lost to space.

2. Explain the significance of the shift inwavelength of the suns radiation when itis reflected from the earths surface.

3. Why does the equator receive more energyfrom the sun than the poles?

4. What is the greenhouse effect?

Evidence for and Impact of Global

Climate Change

There is overwhelming evidence that theearths climate has changed often overthe centuries. Figure 3.7 shows thechanges in Greenlands climate over thepast 75,000 years. We can see from

figure 3.7 that the climate has only been warmer than pre-sent levels for about 15% of the past 75,000 years. We canalso see that temperatures have varied even within shortperiods of time, and in some cases this has had majoreffects on human activities such as fishing and farming.

Obviously, the changes shown in figure 3.7 are due tonatural causes, as the number of humans for most of the

past 75,000 years was far too small to have any significantimpact on the environment at a global scale. The natural

3.8 A small glacier in the Altay Mountains (Mongolia). A fewdecades ago, the ice of the glacier covered the entire valley area in theforeground where moraine has now been deposited.

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3.6 Farmers use green-houses to build up heatfor the cultivation ofvegetables in cool cli-mates. This farmer nearWuhan in China hasremoved the plastic cover-ing with the arrival ofspring to show the cab-bages that grew in thegreenhouse while it wassnowing outside. Heatbuilds up in the earthsatmosphere like a green-house.

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3.7 Temperature changes in Greenland over thepast 75,000 years. In (a) we see that the lastgreat ice age ended about 11,000 years ago. In (b)we see that average temperatures for the past

1000 years were lower than in this century, withthe period 1930 to 1970 being particularly mild.In (c) we note that large temperature changes canoccur quite suddenly, and that both cooler andwarmer periods can have warm or cold years.




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causes for climate change might include changes in levelsof solar activity, the impact of volcanic activity (extra dustin the atmosphere can lead to cooling), variations in theearths orbit (perhaps with changing distances from thesun) and changes in the humidity and cloud cover.

However, there is evidence of a different trend in globaltemperatures in recent decades, including the following:

Arctic sea ice is melting at a rapid rate; it is 40% thin-ner now than it was forty years ago.

All major non-polar glacial systems are in rapid re-treat (figure 3.8); the permanent snows on MountKilimanjaro in Africa may disappear within a decadeor two.

Throughout the northern hemisphere, ice forms onlakes about a week later than it did a century ago,and it melts about a week earlier.

The timing of egg-laying for animals and the flower-ing of plants has changed as climates have warmed,and the distributions of plants and animals have alsoshifted as habitats have changed.

Precipitation has increased across the northernhemisphere, especially destructive rain storms.

El Nio events, which are huge and sometimesdestructive effects caused by ocean warming in thetropical Pacific Ocean, have become more frequent,persistent and intense since the mid-1970s.

Changes in global . . .

CO2 concentration (parts per million)

TEMPERATURE (oC)700

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3.9 Changes in carbon dioxide concentration and global temperaturesfrom 1860 to the present (actual) and from the present to 2100 (pro-jected).

The scale of the changes in global temperatures sinceabout 1980 are unprecedented, and this leads many re-searchers to hypothesise that human activity may be a

significant part of the cause. There seems little doubt thatglobal warming is occurring, although some researcherscontinue to question whether it is due to natural

processes or human activities such as the consumptionof fossil fuels. If global warming is mainly caused byhuman actions, then it could well be the most significantenvironmental issue faced by humanity because theimplications are so great (figure 3.9).

It is expected that temperature increases will reduce cropyieldsin most tropical and sub-tropical regions of the

world, where food is most scarce. On the other hand,increases in summer rainfall may benefit crop productionand commercial forestry in some areas, particularly inSouth Asia.

Warming temperatures would also mean less availabilityof waterin arid regions as well as a higher risk of flood-ing from heavier rainfall in temperate regions. This para-dox arises because warm air holds more water vapourthan cold, and so both evaporation in dry areas anddownpours in wet areas increase. Some forecasterssuggest that areas currently experiencing frequent water

crises, such as north-east China and the flood-prone riverdeltas of Bangladesh and Vietnam, may experience large-scale land degradationand loss of soil in a changing cli-mate. For the worlds least developed countries, agricul-tural impacts such as these may threaten not only foodsecurity, but also national economic productivity.

3.10 Global warming could melt polar ice caps and icebergs, causing arise in the worlds sea levels, flooding many low lying coastal areas andislands. The lake where these icebergs are floating at Jkulsrln(Iceland) used to be filled with a glacier of solid ice. Will icebergs existhere in 50 years, or will this scene just be a coastal lagoon?

It is also suggested that rising sea levelscould floodmany low-lying areas and even submerge some islandand delta countries (figure 3.10). It is important to notethat a rise in sea level does not happen simply becausethe polar ice caps begin melting, for the same reason thatmelting an ice cube in a drink does not raise the level ofliquid in a glass. The rise in sea level of about 30 centime-tres would result mostly from the thermal expansion ofhotter water. If this occurs, other impacts will include

aggravated erosion from the rising sea levels, the dis-placement of people in coastal communities, and in-creased costs to manage coastal defences (figures 3.11 and


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3.12). The impacts of sea level changes are likely to affectthe worlds poorest most as they cannot afford the expen-sive engineering solutions required to give protectionagainst rising sea levels.

3.11 One of many houses built in very vulnerable locations on thebeach front in North Carolina.

3.12 These dunes on the North Carolina coastline have been strength-ened by planting salt-tolerant grasses to guard against erosion by waveattack.

The evidence to support rising sea levels is mixed.According to satellite measurements, a global rise in sealevels is occurring, but it is only about 2 millimetres peryear. However, there are wide local variations in the riseand fall of sea levels in various parts of the world, andthese variations have a wide range of about 100 millime-tres per year, with most parts of the world showingdownward trends. Historical records show no accelera-tion in sea level rise during the 20th century. The situa-tion continues to be monitored, especially in the placesthat would be most affected such as the low-lying riverdeltas of countries such as Bangladesh, India, Philippines,Vietnam, and China, as well as the small island states ofthe Pacific Ocean (figure 3.13).

Other predictions are that a warmer and wetter world willfavour mosquitoes, and so more people will be exposed todiseasessuch as malaria and dengue fever. As many ofthe diseases that will spread are tropical, they are likely to

affect those who can least afford to pay for treatment andare thus the most vulnerable. On the other hand, manyindigenous peoples who practise traditional lifestyles andlive in harmony with their environments are so in-tunewith the land and have such adaptable lifestyles that theymay be able to withstand these impacts. Nonetheless,some forecasts suggest rising temperatures will exposemillions of additional individuals to infectious diseasesand heat-related deaths by 2100, although highertemperatures may also reduce the risk of cold-weatherrelated deaths in other areas.

3.13 These stilt houses, built over the shoreline near Manila (Philip-pines) are especially vulnerable to damage, especially during typhoons.

3.14 On the elevated Tibetan plateau in China, growth of vegetation islimited by the cold, dry climate.

More and more people now believe that humans arereducing the earths capacity to absorb greenhouse gasesby reducing biodiversityand cutting down large areas offorest (deforestation). Through the process of deforesta-tion, humans have increased the concentration of green-house gases in the atmosphere by releasing large quanti-ties of stored carbon dioxide. These gases absorb infraredradiation, and therefore they retain energy that wouldhave otherwise escaped back into space. The impact of

climate change on ecosystems and biodiversity will varyin different environments. For example, coral reefs arelikely to be damaged by increases in the frequency of




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bleaching events, while estimates suggest that the Asia-Pacific region may lose up to 13% of its mangrove wet-lands. Changes in high altitude environments such as theTibetan Plateau may see desert and steppe systems giveway to forests and grasslands (figure 3.14). Meanwhile,the grasslands of central Asia are projected to decline,while wildfires and dieback diseases may affect some

tropical forests.

Yet another concern is thatglobal warming might causetropical cyclones and hurri-canes to become more fre-quent or more intense.Tropical cyclones, which arealso known as typhoonsandhurricanes, are highly in-tense low pressure cells,with winds generally ex-

ceeding 120 kilometres perhour. They spend most oftheir lives over the warmoceans from which theydraw their energy and mois-ture (figure 3.15). Whentropical cyclones move overland or over cooler water,they tend to lose strength.When they move into popu-lated areas, they create a sig-

nificant hazard as buildingsare destroyed, and debris isblown about (figure 3.16).The winds in tropical cy-clones can tear roofs awayfrom buildings, uproot trees,and damage power lines andcommunications. Additionalhazards that can arise fromtropical cyclones includecoastal flooding and stormsurges, which are rises inocean levels produced byhigh winds and low atmos-pheric pressure. Besidescausing flooding, stormsurges can also increasecoastal erosion, potentiallycausing slope failures.Tropical cyclones can evenstart fires by damagingpower lines. Contaminationof drinking water and dis-

ruption of utility services, such as electricity, sewers andcommunications, are also common occurrences duringtropical cyclones.

The argument that global warming might cause tropicalcyclones to become more severe is based on the assump-tion that sea surface temperatures will increase as the

climate becomes warmer warm oceans provide most of

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3.15 The world distribution oftropical cyclones, 2006 (top) to2009 (bottom).


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the energy supply for tropical cyclones. Once again, theevidence for this argument is ambiguous. According toLandsea (1996), there has been a general decrease in thenumber of intense tropical cyclones in the North Atlantichurricanes since the mid-1970s, although the mid-1990ssaw a more active tropical cyclone trend in the Atlantic.Many climatologists conclude that although global warm-ing has some effects on the frequency and intensity of

tropical cyclones, most of the variations are due to naturalfactors such as ocean temperatures and the movements ofocean currents..

3.16 Typhoon damage in Manila, the capital city of the Philippines.

It is possible that some other hazards may become moresevere or frequent if global warming occurs. If climatesbecome warmer, it seems likely that the number of thun-

derstormswith extreme rainfall, tornadoes and hail, heatwaves, floods and drought will increase in specific areas;while the frequency of cold waves will become rarer. Therelationship between the frequency and intensity of tropi-cal cyclones and global warming is inconclusive. Someparts of the world will probably benefit if global warmingoccurs, because increased rainfall and warmer tempera-tures will enhance conditions for growing crops, andyields of food should increase.

Nonetheless, global warming is likely to carry seriousfinancial costs in addition to the social costs mentioned

above. Estimates of these financial costs vary dependingon the impacts that are forecast, but estimates of about$US 5 trillion over the next century are common. Thesecosts may be needed in areas such as agriculture, forestry,fisheries, water supply, energy, infrastructure, cyclonedamage, drought damage, coastal protection, loss of landdue to rising seas, loss of wetlands, loss of forests, loss ofspecies, loss of human life, pollution and migration. Mostof these costs will be felt in LEDCs because they arepoorer and therefore have less capacity to cope withproblems. It is said that the MEDCs in temperate areasmay even benefit if global warming occurs, provided theextent of warming is only 2C to 3C, because of theimproved crop yields mentioned earlier.

Another aspect of the financial costs are the psychologicalcosts. In 2008, the first case of climate change delusionwas reported when an anxious and depressed 17-year-oldboy was admitted to the psychiatric unit at the RoyalChildrens Hospital in Melbourne. He was refusing todrink water because he was so concerned that a droughtat the time was related to climate change. The young manwas convinced that if he drank water, millions of people

would die as a consequence. There is evidence that ex-treme weather events, such as droughts, typhoons, floods,and cyclones, can cause emotional distress which in turncan trigger conditions such as as depression or post-traumatic stress disorder where the bodys fear andarousal systems become heightened. If climate changedelusion becomes more common, the demands on themental health industry could become significant.

On balance, researchers believe that the net effects ofglobal warming are most likely to be negative for a major-ity of the worlds economies. This will be the result ofdifferent factors in different countries. In those countrieswhere long-term, sustainable economic development canbe achieved, these economic impacts may simply serve toslow the rate of economic growth. In other countries,especially the poorer countries that are more dependenton the natural environment, then the impact of climatechange on the economy could be extremely damaging,and in the case of some specific industries such as fishingand cropping, the impact could be ruinous.

Q U E S T I O N B L O C K 3 C

1. Most geographers agree that climate change is caused by amix of natural and human factors. There is no consensus onhow important each of these factors is in the global warmingcurrently being experienced. Why do you think it has beenso difficult to reach a consensus on the relative importance ofnatural and human factors?

2. Make a point form list of the impacts of global warmingcovered in this section in descending order of importance.

3. Give reasons to explain why you placed your first rankedand your last ranked points in the positions you chose when

you answered the previous question.

4. How do the likely and possible effects of global warmingimpact people in LEDCs and MEDCs differently?

5. Does global warming cause more intense tropical cycloneactivity? Give reasons to support your answer.

Atmospheric Carbon Dioxide

Some gases retain heat especially well, and one of these iscarbon dioxide (CO2). Carbon dioxide is an important by-product of many manufacturing processes (figure 3.17).Since the beginning of the industrial revolution, the con-centration of carbon dioxide has increased by 36%, while




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two other greenhouse gases(gases that retain heat),nitrous oxide and methane, have increased by 17% and151% respectively. Although not all researchers agree, amajority claim that as a result of this build-up of green-house gases, average global temperatures rose by 0.8Csince 1880, and the trend seems to be accelerating.

Measurements of atmospheric carbon dioxide(CO2) con-

centrations have been taken at Mauna Loa in Hawaii for alonger time than anywhere else in the world. Mauna Loais considered one of the best locations for measuringundisturbed air because local influences on atmosphericCO2concentrations are minimal, and any influences fromnearby volcanoes can easily be excluded from the records.The methods and equipment used to obtain measure-ments have remained unchanged since the monitoringprogram began in 1959.

The Mauna Loa record shows a mean annual increase of17.4% in the average annual concentration of CO2, risingfrom 315.98 parts per million by volume (ppmv) of dry airin 1959 to 383.57 ppmv in 2007. This is the highest level ofCO2concentration at any time during the past 160,000years. It represents an average annual growth rate of 1.43ppmv per year, although in 1997-98 an abnormally largeincrease of 2.87 ppmv occurred. At the time the industrialrevolution began, the concentration was about 280 ppmv,and this figure had remained fairly constant since theend of the last ice age 14,000 years ago, when theconcentration increased from about 190 ppmv.

Scientists disagree over whether or not increasing the CO2concentration leads to global warming. Some argue thatduring the period 1940 to 1980, when carbon dioxideemissions were rising most rapidly, global temperaturesactually fell, which is why there were widespread predic-tions of an imminent ice age during the 1970s. However,during the period with the most reliable data (since 1960),global average surface temperature has increased bybetween 0.2C and 0.3C.

Still other researchers dispute the cause-and-effect rela-tionship between carbon dioxide and global warming. As

outlined in the ToK Box in this chapter, some researchersagree that there is a positive correlation between levels ofatmospheric carbon dioxide and global warming, butclaim it is rising temperatures that cause the increase incarbon dioxide levels, not vice versa.

If we take a long time frame, global mean surface airtemperatures have increased by between about 0.3C and0.6C since the 1890s. This trend has not been uniformacross the world, however. Some areas, such as the conti-nental areas between 40N and 70N, have warmed morethan the average, while other parts of the world, such as

the North Atlantic Ocean, have cooled slightly during thepast century. Clearly, the physics behind the greenhouse

effect, and the atmospheres capacity to regulate itself, arevery complex and still not well understood.

3.17 Greenhouse gas and particulate emissions from a coal-fired powerstation in Pyongyang, North Korea.

The Kyoto Protocol and the IPCC

In December 1997, world leaders met in Kyoto, Japan, toconsider a world treaty that would restrict emissions ofgreenhouse gases, especially carbon dioxide. It wasagreed that carbon dioxide levels had increased substan-tially since the time of the industrial revolution, and thatthis trend was expected to continue. It was also agreedthat humans had been responsible for much of this in-crease. However, there was disagreement over how muchof the increase in temperatures had been due to the

increase in carbon dioxide concentrations. Some arguedthat more greenhouse gases in the future would raise theearths temperatures, causing the polar ice caps to meltpartially, raising sea levels and flooding low-lying coastalareas and islands. On the other hand, others argued thatgreenhouse gases support plant life, and thus the animallife that depends upon it would thrive with an increase incarbon dioxide levels. These commentators argued thatwhat humanity is doing is simply liberating carbon frombeneath the earths surface and putting it into theatmosphere, where it is available for conversion intoliving organisms.

It is agreed by people from all points of view that thegreenhouse effect is certainly real. Greenhouse gases suchas H2O (water vapour) and CO2in the atmosphere reducethe escape of long-wave infrared radiation (heat) from theearth into space. Therefore, when we increase the concen-tration of carbon dioxide, we effectively increase theenergy input to the earth. However, as shown in figure3.2 earlier in this chapter, what happens to this heatenergy is complex. The energy is redistributed verticallyand horizontally by various physical processes, includingadvection, convection, and diffusion in the atmosphereand ocean.


C H A P T E R 3


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At the end of the Kyoto meeting, 38 industrialised coun-tries agreed to cut their emissions of six greenhouse gasesthat were linked to global warming. An agreement wassigned, which has become known as the Kyoto Protocol.Then, in July 2001, a further meeting of delegates from 180countries was held in Bonn (Germany) to work out detailsof implementing the Kyoto Protocol. It was agreed in

Bonn that the Kyoto Protocol would not take effect until itis ratified by 55% of the nations responsible for at least55% of the greenhouse gas emissions. The countries(mainly MEDCs) that agree to ratify the Protocol areobliged to reduce emissions of carbon dioxide to anaverage of 5.2% below 1990 levels during the five-yearperiod 2008 to 2012. Compared with not doing anything,this initiative represents a reduction of almost 30% ingreenhouse gas emissions. The emissions of LEDCs willbe controlled by subsequent negotiations under theclimate treaty.

Opinions differ as to how effective the Kyoto Protocol willbe. It has been calculated that an expected increase inglobal temperatures of 2.1C by 2100 will only be reducedto an increase of 1.9C under the Kyoto Protocol.Expressed another way, the temperature that would have

been experienced in 2094 would merely be postponed bysix years until 2100 under the Kyoto Protocol. For thisreason, some critics of the Protocol say it is far too weak,while others argue that its financial cost ($US 150 billionto $US 350 billion annually) is not justified for the tokenis-tic gains that are achieved. As Lomborg (2001) comments:

Because global warming will primarily hurt Third World

countries, we have to ask if Kyoto is the best way to help them.The answer is no. For the cost of Kyoto in just 2010, we couldonce and for all solve the single biggest problem on earth: Wecould give clean drinking water and sanitation to every singlehuman being on the planet. This would save two million livesand avoid half a billion severe illnesses every year. And forevery following year we could then do something equally good.

In February 2005, the BBC conducted a survey of almost2000 world-wide on the issue of climate change. Some ofthe key results are shown in figure 3.18.

Significant work on the issue of climate change has beenundertaken by a group known as the IntergovernmentalPanel on Climate Change(IPCC), established jointly bytwo United nations bodies, the UNEP and the WMO. TheIPCC comprises several hundred of the worlds leading

110

60%

50%

40%

30%

20%

10%

0%

Very

Concerned

Concerned

No

Opinion

/

DontKnow

NotVery

Concerned

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Concerned

AtAll

Increased

Temperatures

Rising

Sea

Levels

Increased

Malaria

Impacton

HumanHealth

IncreaseinExtreme

WeatherEvents

Environmental

Impacts

Other

How concerned are you

about climatic change?70%

60%

50%

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30%

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0%

TheWorldisTaking

Climate

Change

SeriouslyEnough

ThereisNothingthe

World

CanDoto

Stop

Climate

Change

MED

CsAreMoreto

Blame

for

Climate

ChangeThanLED

Cs

Climate

Changeis

Unproven

MoreUseNeedstoBe

Madeo

fRenewable

Energy

Sources

ItisNotEconomically

ViabletoHault

Climate

Change

To what extent do you agree with the following

statements?30%

20%

10%

0%

What aspect of climate

change most disturbs you?

Very

Effe

ctive

Effe

ctive

D

ont

K

now

Ine

ffe

ctive

Very

Ine

ffe

ctive

40%

30%

20%

10%

0%

Dont

Know

M

aybe

No

Yes

60%

50%

40%

30%

20%

10%

0%

Do you think the Kyoto

Protocol does enough to halt

climate change?

How effective do you think

the Kyoto Protocol will be at

fighting Global Warming?

Strongly disagree

Disagree

Neither

Agree

Strongly agree

90%

80%

70%

60%

50%

40%

30%

20%

10%

0%

Recycling

Composting

Walk

ingor

Cycling

B

uyingEnergy

Efficie

ntAppliances

UsingEnergy

Efficie

ntAppliances

Im

provingYour

H

omesEnergy

Efficiency

Do you personally make a conscious effort to

reduce levels of climate change by:

Yes

No

3.18 Results from a world-wide survey on attitudes to climate change conducted by the BBC in February 2005 (Source: extracted fromwww.bbcworldpanel.com/reports.php?&aid=793523597). It would be interesting to compare these results to the attitudes of the members ofyour class.




12/45

scientists and researchers. Several reports have beenpublished by the IPCC that contrast strongly with viewsof some governments and critics such as Bjrn Lomborg.

The report of the IPCC consists of four large volumes thatwere finalised at conferences held in Shanghai, Genevaand Accra in late 2000 and early 2001. The report suggeststhat humanity stands on the edge of cataclysm as a con-

sequence of global warming. Extensive measurementshave been undertaken in the upper atmosphere, under thesea, on tundra and desert, permafrost and ice caps, in treerings and glacial ice cores, in pollen sediments and birdnesting records, with satellites and weather balloons.Computer models were developed to a high degree ofaccuracy, with the models being tested by looking at pastclimates, and tracking chemicals released in the 1991eruption of Mount Pinatubo in the Philippines. Theresearch has been analysed by an international team ofresearchers who were charged with reaching a consensus

on global warming.The preliminary finding in 1995 concluded that the bal-ance of evidence suggests a discernible human influenceon global climate. The conclusion reached in 2001 wasconsiderably more alarming. Using six different projec-tions about how economies would grow and how theywould make the transition to non-carbon forms of energy,it was concluded that the global average temperaturewould rise by 1.7C to 6.1C before 2100. This was a morepessimistic projection that the 1996 conclusion, whichforecast a rise in temperatures before 2100 of between

1.1C and 4.0C.

If this forecast comes true, the earth will be transformedinto a planet unlike anything that humans have everexperienced. The current global average temperature is15C, but this could rise to as much as 21C. Thistemperature would mean a huge rise in the amount ofenergy trapped in the lower atmosphere, increasing therate of almost every natural process except the volcanicand the tectonic.

The IPCC argues that there is now no doubt that the

earths climate is warming. Among the evidence of this,the IPCC says that average global surface temperaturesincreased by about 0.6C between 1900 and 2000, snowcover and ice extent have decreased, hurricane activityhas increased ,and average sea levels have increased. TheIPCC notes that the biggest increases in temperatureshave been in the lowest 8 kilometres of the atmosphere,which is where human impacts are greatest. The IPCC isextremely critical of the emissions of greenhouse gasesand aerosols because of the impact they cause (figure3.19). This is why the Kyoto Protocol calls for immediatereductions of greenhouse gas emissions by MEDCs.

The trend of global warming has been likened to theshape of hockey stick, as there is a sharp rise beginning at

the start of the Industrial Revolution. The IPCC predictsthat this trend will continue unless significant actions aretaken to reverse the production of greenhouse gases andstrengthen the directions of the Kyoto Protocol.

The IPCCs predictions have been challenged, however.The IPCC used market-based exchange rates as the finan-cial basis of its predictions, whereas critics argue it should

have used the more realistic Purchasing Power Parity(PPP) method, as described in chapter 2 of this book. ThePPP method adjusts wealth according to the spendingpower of different countries rather than an often artificialexchange rate. Critics of the IPCC claim that in usingmarket-based exchange rates, the IPCC has over-predicted future economic growth, and thereforeemissions growth.

360

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Carbon dioxide

Methane

Nitrous oxide

CO2

(ppm)

CH4

(ppb)

N2O(ppb)

1000 1200 1400 1600 1800 2000

Year

Atmosp

hericConcentration

Radia

tiveForcing(Wm-2)

3.19 Global atmospheric concentrations of three greenhouse gases. Theleft axes show concentrations in parts per billion (ppb). The right axesshow the estimated radiative forcing, which is the change in the balancebetween radiation entering the atmosphere and radiation leaving. It isthus a measure of the temperature rise that results from the change ingas concentration. Because these three gases have atmospheric lifetimesof over a decade, they are well mixed and the concentrations reflectfigures throughout the globe. All three gases show sharp rises as aresult of human activity during the industrial era. The shapes of thecurves are sometimes known as the hockey stick effect. (Source:IPCC, Third Assessment Report)

The IPCCs predictions are certainly serious, and if true,

represent a very significant global challenge for humanity.According to the organisation, average global tempera-tures will rise between 1.4C and 5.8C, which is a morerapid rate than 1900 to 1990, and probably the most rapid


C H A P T E R 3


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rise for at least 10,000 years. This will result in highermaximum and minimum temperatures, more hot days,fewer cold days, reduced diurnal ranges of temperatures,shrinking ice and snow cover, retreat of glaciers, morefrequent droughts and more intense tropical cyclones.The IPCC also predicts that the tropical Pacific Ocean willbecome more El Nio-like, with the eastern Pacific warm-ing more than the western Pacific, and therefore a shift in

precipitation in the same direction. Among the otherpredictions made by the IPCC are that average globalprecipitation will increase, although variations in

precipitation from year to year will also increase, whileglobal sea levels will increase by between 0.09 and 0.88metres between 1990 and 2100.

If the predictions are correct, the consequences of globalwarming are likely to be felt globally in a multitude ofways. Figure 3.20 looks complex, but it is an attempt tosimplify the intricate and convoluted consequences ofglobal climate change. Some of the consequences havealready been examined, but 15 of the links that areidentified by number in figure 3.20 require a little moreexplanation:

112

3.20 Causes andConsequences ofGlobal ClimateChange Arrowsindicate cause-and-effectrelationships.Double-headedarrows indicateinterdependen-cies. The num-bers indicatesome less obvious

linkages that areexplained in thetext.




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1. More frequent and severe droughts could lead directlyto conflict because of tensions over water resources,especially between upstream and downstream areas ofthe same catchment, or between different countries thatshare the same underground aquifer, especially if oneside accuses the other of stealing water. The IPCCprojects that by 2050, more than one billion people in

Asia could be adversely affected by decreased wateravailability.

2. More frequent and severe droughts can ruin harvests,leading to malnutrition and migrations in search ofwater and pasture. The IPCC forecasts that in AfricaBy 2020, between 75 and 250 million people areprojected to be exposed to an increase of water stressdue to climate change.

3. Acidification of the oceans due to increased absorptionof CO2can hinder the formation of shells and skeletonsof marine organisms, adversely affecting marine ecosys-tems. This is discussed in greater detail in chapter 6.

4. Rising sea levels are expected to cause large-scale mi-grations of people, escaping not only the permanentlyhigher sea levels, but also the increased frequency offlooding in more elevated areas due to storm surgesthat cover farmlands with salt water, as well as con-taminating fresh water wells and aquifers. A WorldBank study in 2007 calculated that a 1 metre rise in sealevels would affect at least 56 million people globally.

5. More frequent tropical storms increase the number of

fires started by lightning strikes.

6. Loss of biodiversity occurs when climate changes fasterthan organisms can migrate or adapt. When criticallyimportant species in a food web are lost, the ecosystemcan collapse. This may have devastating consequencesfor the species directly involved, but it also has severeconsequences on economic systems because of itsimpact on agriculture and tourism, as well as throughthe loss of irreplaceable natural chemical compoundsfor pharmaceutical and bioscience research.

7. More frequent and severe tropical storms can leaddirectly to migrations of people from low-lying areastrying to escape the devastation and the loss of farm-land and clean water due to saltwater contamination bystorm surges.

8. Large-scale population movements are very likely tolead to conflicts as people try to cross borders and settleon land that is already claimed by others.

9. All of the economic costs of global warming willindirectly affect the insurance industry, which will re-

sult in higher premiums.

10. Higher insurance costs will affect companies thatgenerate energy, and these higher energy costs will bepassed on to consumers.

11. Higher insurance costs directly impoverish people bymaking insurance unaffordable to some folk whopreviously would have been able to afford it.

12. More frequent and severe floods contaminate watersupplies leading directly to outbreaks of cholera,diarrhoea and other water-borne diseases.

13. Higher energy costs lead directly to worse health caresince they increase transport, heating and electricitycosts for the health sector.

14. Donor fatigue is likely to become a significant problemwith the increased frequency and severity of droughts,floods, tropical storms, heat waves and forest fires, thespread of tropical diseases, a likely increase in conflicts

and the increased costs of energy and other economiccosts facing donor countries.

15. The ageing of donor countries populations willincrease donors health care costs at the same time as itshrinks their tax bases. This is likely to be one of themain sources of pressure on donors aid budgets notbecause older people are any less generous thanyounger people, but because the higher health carecosts will erode public finances as people live longerand there are fewer workers per retiree.

Not all climate change forecasts predict catastrophe.Perhaps Russia has the potential to gain the most fromclimate warming. Russia has huge untapped reserves ofnatural gas and oil in Siberia and also offshore in theArctic Sea, and warmer temperatures would make theseenergy reserves much more accessible. Presuming(maybe wrongly) that oil and natural gas continue beused in large quantities as global warming continues, thenthis would mean a big boost for the Russian economygiven that 80% of its exports and 32% of its governmentrevenues presently come from the production of energyand raw materials. Furthermore, the opening of an Arctic

waterway for shipping could provide economic andcommercial advantages for Russias foreign trade.

Canada is another country that might benefit from globalwarming as it would escape several climate-relateddevelopments such as intense hurricanes and heat waves.Furthermore, global warming could open up vast areas ofland that is currently covered by snow for most of theyear to development. If temperatures rose, access forshipping to Hudson Bay would be improved, and it ispossible that new polar shipping routes could be opened.Furthermore, the length of the growing seasons for agri-

culture would increase, the energy demand for heatingand cooling will probably fall, and productive forestswould be expected to expand into the tundra.


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114

In 2006, Al Gore released a movie aboutclimate change called An InconvenientTruth. The movies release was widelyregarded as one of the most importantactions in making the general public

aware of climate change as an issue. AlGore was awarded the Nobel PeacePrize, largely in recognition of themovies effectiveness in alerting peopleto the issue of climate change.

By using the title An InconvenientTruth, Al Gore was stating that theclaims made in the movie are truth.Every geographer would acknowledgethat global temperatures change overtime how else could we have had iceages? However, the central claim of AnInconvenient Truth is that the warming

of the worlds temperatures today isunprecedented in human history, andthese changes are primarily caused byhuman actions. This claim is notaccepted by all geographers.

The central theses of An InconvenientTruth are that global warming is real,that anthropogenic forcing (human ac-tions) is the primary cause, that globalwarming will result in a catastrophicloss of both human and animal life, thatglobal warming is causing increasedstorm intensity, and that we have passedthe tipping point so that global warmingwill continue to accelerate out of control.

The four main scientific points made inAn Inconvenient Truth were:

1. Global average temperatures havebeen rising significantly over the pasthalf centuryand are likely to continue torise (climate change);

2. Climate change is mainly attributableto human-generated emissionsofcarbon dioxide, methane and nitrousoxide (greenhouse gases);

3.Climate change will, if unchecked,

have significant adverse effectson theworld and its populations; and

4. There are measures which individualsand governments can takewhich willhelp to reduce climate change ormitigate its effects.

The central piece of evidence used in thefilm was an analysis of the trend ofannual temperatures and carbon dioxide(CO2) levels for the past 650,000 years inAntarctic ice core samples. In themovie, Al Gore discusses the possibilityof the collapse of a major ice sheet inGreenland or in West Antarctica, eitherof which could raise global sea levels,flooding coastal areas and producingmillions of refugees. Melt water from

Greenland, because of its lower salinity,could halt the currents that keep north-ern Europe warm and quickly triggerdramatic local cooling there.

Gore quoted US Geological Surveypredictions that that by 2030, GlacierNational Park will have no glaciers left.He also quoted figures, such as in thelast 30 years, over one million squarekilometres of Arctic sea ice have melted,and thus polar bears today drown whenthey cannot find an ice floe on which torest.

Almost as soon as it was released, AnInconvenient Truth provoked contro-versy. Some of the attacks were frompolitical lobby groups, others from the

energy industry, while still others werefrom dissenting scientists and geogra-phers who disputed Gores interpreta-tion of the evidence he had selected topresent.

In 2007, as a response to An Inconven-ient Truth, a documentary called TheGreat Global Warming Swindle wasshown by Britains Channel 4. Thisdocumentary quoted an impressivearray of scientists and geographers fromaround the world and providedevidence to support 14 claims againstthe thesis of man-made (anthropogenic,or human-induced) global warming:

1. Evidence from many sources,including Antarctic ice cores and the lageffects shown in contemporary

measurements, shows that althoughthere is a relationship betweenatmospheric carbon dioxide and globaltemperatures,it is rising temperaturesthat cause the rise in CO2, not vice versaas is often claimed.

2. From the 1940s to the early 1980s,the earth experienced a significantperiod of cooling, even though this wasthe period during which industrial pro-duction and carbon dioxide productionrose most sharply. That explains thewidespread concerns about the onset of

an imminent ice age during the 1970s.3. Water vapour and methane are farmore significant greenhouse gases thancarbon dioxide, both in terms of volumeand impact. To ignore them and focuson carbon dioxide is to miss the realcauses of climate change. Statistically,fluctuations in all three gases are over-whelmingly dominated by naturalrather than human causes.

4. Sun spot activity and levels of solarradiation parallel temperature changesmuch more closely than carbon dioxide

levels, and these natural causes have adirect bearing on atmospheric watervapour and (to a lesser extent) methanelevels.

5. If rising carbon dioxide levels werethe main cause of anthropogenic(human-induced) global warming, thenthe troposphere (the layer of the earthsatmosphere about 10 to 15 kilometresabove the surface) should heat up fasterthan the earths surface. However, datacollected from satellites and weatherballoons show that this is not so, and in

fact there is a slight opposite trend.6. The proportion of carbon dioxide inthe atmosphere produced by humans isextremely small (about 3%)compared

ToK BoX Truth and Global Warming.




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115

with the amounts produced naturally byanimals, bacteria, decaying vegetation,the ocean and volcanoes; the humancarbon footprint is vastly outweighedby these other factors.

7. In the 1970s, scientific concernsfocused on the imminent onset of a newice age. The more recent concern about

global warming since the 1980s waspolitically motivated, the origins beingthe British Prime Minister, MargaretThatchers wish to promote nuclearenergyby denigrating coal-basedelectricity generation.

8. There is a vested interest amongresearcherstoday to highlight andexaggerate the potential catastrophe ofglobal warming because so much fund-ingis available for this purpose, and avery powerful anti-global warming in-dustry has grown up. There is evidence

of research being falsified to sensational-ise the potential dangers of globalwarming.

9. Rising sea levels due to melting icecaps are extremely unlikelybecause sealevels are less dependent on the volumeof ocean water than thermal expansionand contraction. The video clips weoften see of collapsing ice sheets aresimply the annual spring thawing.

10. Historical evidence of past warminterglacial periods shows that althoughfarmers in some areas may suffer, many

more farmers are likely to prosperifglobal warming continues due toincreased rainfall that is more reliablethan at present.

11. Global warming activists claim thatnatural disasters such as hurricanes andtyphoons are likely to increase infrequency and severity with globalwarming. However, between theequator and the polesthe opposite ismore likely because the severity ofextreme atmospheric events is deter-mined by the differential conditions, but

with global warming these differencesare reduced, not increased.

12. Global warming activists arguethat LEDCs (less economically devel-oped countries) need to adopt pathwaysto development that produce less carbon(such as wind, tidal and solar power),even though these strategies are usuallytoo expensive even for MEDCs (MoreEconomically Developed Countries) toadopt. This is a concern because it isseen by people in LEDCs to be an at-tempt to perpetuate and even widen thegap between rich and poor.

13. Global warming is being used as aweapon by some governmentstoimpose taxes, reduce personal freedoms,

change labour regulations etc for pur-poses that are not connected with globalwarming. Carbon futures trading is anespecially insidious form of the richprofiteering at the expense of the poor.

14. At the time that the UN report bythe Intergovernmental Panel on ClimateChange (IPCC) was published, it was

said to have been supportedunanimously by more than 2,000 of theworlds leading scientists. However,several scientists now claim it was asham given that this list included thenames of scientists who disagreed withits findings. Professor Reiter, of the Pas-teur Institute in Paris, for example, saidhis name was removed from an assess-ment only when he threatened legalaction against the panel. Other scien-tists claim their names were included inthe report against their wishes.

15. NASA data suggests thatall theplanets of our solar system may bewarming at about the same percentagerate as Earth with no help fromhumans.

How can we judge truth claims such asthose made in An Inconvenient Truthand The Great Global Warming Swin-dle? Many maybe most peopletoday would probably agree with the

claim that humans are the main cause ofglobal warming, but that would be avery weak basis to say the statement istrue.

It may be helpful to understand thatthere are three different theories of truthagainst which we can test this (and anyother) truth claim!

One theory is the Correspondence The-ory of Truth. Under this theory, a state-ment is true if and only if it correspondsto a fact. The fact should be independ-ent of language, society and culture.Grass is green is true if and only if thegrass the green. People who hold the

correspondence theory of truth arecalled realists.

Another theory is the Coherence Theoryof Truth. Under this theory, a statementis true if it is consistent with other truestatements within a belief system.People who hold the coherence theoryof truth are called anti-realists. Whereas

realists go out and look for evidence,anti-realists sit and think about consis-tency. For an anti-realist, the statementthe world is flat was once true becauseit conformed to the broad consensus ofhow people viewed the world, but it isno longer true.

The third theory is the PragmaticTheory of Truth. Under this theory, astatement is true if it is useful or worksin practice. People who hold thepragmatictheory of truth are calledpragmatists. Pragmatism does not

concern itself with facts or coherence.This theory could be summarised as Ifit works, it must be true.

So, to return to the question of globalwarming, consider the claim globalwarming is caused by human actions.For a realist, this would be true if andonly if the factual data supports thestatement.

For an anti-realist, the statement wouldbe true if it reflects the broad consensusof opinion.

For a pragmatist, it would be true if it isuseful, for example, if you can makemoney from the belief, or if it makes youfeel better, or more passionate about acause, or if it serves you politically, andso on.

Being aware of the various theories oftruth, how would YOU go about evalu-ating the claim that global warming iscaused by human actions?

The next ToK BoX is on page 150.


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Further information on climate change, especially itseffects on extreme environments, is provided towards theend of chapter 7. Further information on the interrela-tionship between climate change and the oceans is givenin chapter 6.

Q U E S T I O N B L O C K 3 D

1. Describe and account for the rising level of carbon dioxide inthe atmosphere over the last century or so.

2. Is the growing concentration of CO2in the atmospherecausing global warming? Give reasons to support youranswer.

3. What is the Kyoto Protocol?

4. How effective do you think the Kyoto Protocol has been inaddressing the challenges of climate change?

5. What is the IPCC?

6. How effective do you think the IPCC has been in addressingthe challenges of climate change?

7. Study figure 3.20. Identify the three consequences of climatechange that you think are most significant, and justify yourchoice.

7. If countries such as Canada and Russia are expected tobenefit from global warming, does that mean they have nointerest in working to slow down climate change?

Soil and Change

Soil Formation and Erosion

When rocks are broken down by the processes of weather-ing, small particles become available to be mixed withorganic matter such as humus (decaying plant matter)and animal faeces. Over time, this process results in theformation of a thin layer of soil. As the soil forms, it cansupport the growth of small plants, which add additional

organic matter when they die. Over time, the soil thusdevelops more fully and becomes thicker. Eventually, amature soil may form with layers (called horizons) ofdifferent colours that are roughly parallel to the groundsurface. The collection of horizons at one point is called asoil profile, and it reflects the movement of water andminerals upwards and downwards.

However, the process of soil formation can be arrestedand reversed as soils are degraded. Soil erosionis theremoval and transfer of soil particles from one place toanother, usually by wind or running water. It occurs in

varying degrees on all soils and while it may be a naturalprocess, it is often aggravated by the actions of people.

When erosion proceeds slowly, soils adjust to the surfacechanges and the profile will not change noticeably in theshort-term. Rapid additions of sediment from flooding orerosion of soils from upslope can bury a soil profile, andthe soil-forming processes will then begin acting on thenewly deposited surface. The previous profile is oftenpreserved if the burial is deep.

Erosion that has taken place over a very long period(which we can refer to as geological time), it is termednormal erosion. Its rate is affected by factors such as:

rainfall(its intensity, duration, amount, seasonality);

the nature and intensity of the vegetationcover;

the length and angle of the slopes; and

the likelihoodof soils to erode. This is mainly a result ofcharacteristics like texture, structure and dispersibility.These properties influence infiltration rates and ease ofparticle detachment from the soil surface.

Human activities have often caused an increase in normalerosion rates, and this is termed accelerated erosion (fig-ure 3.21). In both urban and rural areas, tree vegetationhas often been removed. This alters the surface cover in away which exposes soils to additional risks of erosion bywind or water.

3.21 This large sign in China reminds people of the importance of soil

conservation. An example of the consequences of ignoring such mes-sages can be seen in the right-hand lead photo of this chapter (on page100), which shows severe soil erosion near Konso, Ethiopia.

The scale of the global problem of soil degradation iscausing increasing concern. According to a study done atCornell University, soil is being eroded at a rate ten toforty times faster than it is being replenished on an aver-age world-wide basis. As the vast majority of humanfood comes directly or indirectly from croplands, whichare shrinking by more than ten million hectares perannum due to soil erosion, the potential impact on the

human food supply is obvious. The pressure on soils toproduce food is increasing also as the demand increases togrow vegetable-based biofuels and and industrial crops




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such as cotton, both of which require vast areas of farm-land and cleared rainforests.

Wind Erosion

Wind erosion occurs in areas where the soil particles areloosely bound together. In many farming areas, the land

is cultivated to eliminate weeds which compete with thecrops for the limited supplies of moisture and nutrients inthe soil. Soil structures are broken up by cultivation andthis makes the soil particles more vulnerable to beingblown by the wind when they are dry (figure 3.22). Finerparticles such as clay can be transported over greatdistances, while sand can drift across fences, railway lines,crops and roads (figure 3.23).

3.22 Wind erosion of topsoil at Merv, Turkmenistan.

3.23 A sand drift almost blocks the highway near Konye-Urgench innorthern Turkmenistan.

Wheat cultivation in countries like Australia is a marginalactivity where rainfall is relatively low and unreliable.Cultivation of light textured soils in marginal wheat landshas led to desertification, which is the extension or inten-sification of desert conditions. Desertification leads to

reductions in plant productivity, accelerated decline insoil quality and increasing hazards for human occupancy.Large areas of the world are being threatened by desertifi-

cation including west and central Africa as well as parts ofAustralia. Over-grazing in areas south of the SaharaDesert has contributed to an expansion of the desert, withthe edge of the Sahara advancing southwards by about 25kilometres per year, on average, according to somecommentators (figure 3.24).

3.24 Cattle owned by nomadic pastoralists graze on the outskirts ofTimbuktu. Mali.

Water Erosion

Human disturbance of the vegetation cover has sped uprates of water erosion of soils. Soil degradation caused bywater takes two main forms, sheet erosion and gullyerosion.

Sheet erosionis the removal of the surface soil to an evendepth over a wide area (figure 3.25). It often occurs onbare, cultivated ground. If run-off becomes sufficientlyconcentrated and turbulent, channels (gullies) are erodedinto the soil.

3.25 Sheet erosion near Konso, Ethiopia.

Gully erosionis very obvious on cultivated land, and itoccurs mainly after intense or prolonged rainfall (figure3.26). Gullying can be a major problem in areas wherepeople have cleared the natural vegetation, although it isimportant to remember that gullying is a natural process


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that can occur in areas where there has been no humanimpact. Nonetheless, human activities do often acceleratethe rate of already existing erosion.

3.26 Gully erosion near Arba Minch, Ethiopia.

3.27 Wind eroded farming land in the Manakah region of Yemen.

Soil Erosion in Rural Areas

In rural areas, most soil erosion takes place on cultivatedland. This is because land that has been left bare of vege-tation for weeks or months at a time is more exposed tothe actions of wind and water (figure 3.27). The loss of

surface soil lowers crop yields because of reductions in: chemical fertility the top layer, or horizon, of the soil

usually contains more plant nutrients and organic mat-ter than the lower horizons; and

physical constitution the lower horizons often containmore clay than the upper layers and are therefore lessfriable than the surface soil.

Even on cultivated land, the rates of erosion vary becauseof factors such as: local characteristics, such as the steepness of the slope;

land management techniques such as the use of contourbanks; and

the soils physical and chemical properties.

When cultivation occurs in arid areas with steep slopes,the soil is especially vulnerable to degradation. In suchareas, soil degradation can be minimised by using tech-niques such as: constructing terraces or broad contour banks (figure

3.28); planting and harvesting crops on the contours;

using grassed waterways to slow down and disperserunoff (figure 3.29); leaving crop residues rather than burning them; not overgrazing pasture areas (figure 3.30); and organising land uses in such a way that erosion is

minimised.

3.28 Terraces used for farming in the arid mountains of the Manakahregion of Yemen.

3.29 Grassed waterways intersperse this farming land near Hossana inEthiopia to slow down the flow of water, thus reducing erosion.

The pressures of soil degradation are perhaps felt morekeenly in Africa than any other continent because theproductivity of crop cultivation is lower than many otherregions of the world while population growth is morerapid. The Alliance for a Green Revolution in Africa(AGRA) estimates that 75% of Africas farmlands sufferfrom soil degradation. Many of the soils in Africa wereformed from granite rocks and are therefore quite low innutrients that plants can use. Furthermore, granite-basedsoils tends to be quite coarse in texture, and therefore the




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minerals and nutrients are easily leached(dissolved byrainwater and removed from the soil). Given the longhistory of human farming in Africa and the traditionaltechniques used, such as hoes and ploughs, both windand water erosion are significant problems (figure 3.31).

3.30 Cattle grazing in the dry mountains of Nokhur, near the border ofTurkmenistan and Iran.

3.31 Ploughing using traditional tools such as wooden ploughs andcattle near Sodo, Ethiopia.

Like farmers using traditional methods elsewhere, farm-ers in many parts of Africa have have traditionally lefttheir fields fallow, or unused, for a year every so often to

allow the soils natural fertility to return. Farmers whopractised shifting cultivation would allow the field toreturn to its natural state of bushland, and then clear thefield once again by burning the grass and bushes that hadestablished themselves there. The ash produced in thisprocess would replenish the soil and restore much of itsproductivity. However, population growth in recentdecades has increased the pressure on farmland, andfarmers have responded by shortening the fallow periods.As a consequence, soils in many parts of Africa havebecome increasingly degraded. Unfortunately, the tradi-tional methods to restore fertility have not been replacedby new methods of soil management and cropping, partlybecause farmers cannot afford the necessary inputs andpartly as they are unaware of the new techniques.

As soil nutrients are not replenished adequately, a viciouscycle begins in which yields decline, poverty increases,and farmers respond by placing still more pressure uponthe soils, either by shortening the fallow period even moreor by expanding farming into more marginal areas,starting the cycle once again.

One of the significant barriers to addressing the problem

of soil degradation in Africa has been that most farmersare poorly educated and follow traditional methodshanded on to them by their parents. In an effort toovercome this problem, an organisation called theAlliance for a Green Revolution in Africa (AGRA) was setup in 2006 with financial support from The RockefellerFoundation and the Bill and Melinda Gates Foundation.In an effort to give the organisation internationalstanding, it is chaired by the former Secretary-General ofthe United Nations, Kofi Annan, and has offices inNairobi (Kenya) and Accra (Ghana).

AGRA has already begun working with Africangovernments, NGOs, the private sector, other donors, andAfrican farmers to improve the productivity and incomesof resource-poor farmers in Africa. AGRA is investing infour areas that are designed to address the problem of soildegradation: improving knowledge, application and adoption of

integrated soil fertility management; improving economic access to fertilisers for poor

farmers; increasing physical access to fertilisers for poor farmers;

and developing policy and incentives for adoption of

improved soil fertility management practices.

Soil Erosion in Urban Areas

3.32 Changing land use settlement yield in the Piedmont region ofeastern USA.Source: After MG Wolman, A Cycle of Sedimentation and Erosion inUrban River Channels, Geografiska Annaler, vol. 49A, pp. 385-95.

Soil erosion often occurs when previously rural land isconverted to urban uses. The removal of tree and shrubvegetation, which interferes with building construction


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and road preparation, accelerates erosion rates. Figure3.32 shows the sharp increase in sediment loss that occurswhen rural land is converted into an urban area.

When rural land is converted into urban land: soil is compacted by heavy earth-moving machinery

used for site preparation; topsoil can be stripped in the levelling process, thus

exposing the relatively impermeable subsoil to gullyerosion;

stockpiles of loose topsoil are reduced in storms by rills(small channels); and

gullying and rilling are common on compactedroadways, especially if the road pattern has beendesigned to run mainly up-and-down the slope insteadof along the contours.

These disturbances during the construction period fornew urban areas can lead to severe soil erosion. Extrasediment can silt up local drainage lines and waterstorages. Once urban gardens are established androadways have been paved, soil loss is markedly reduced(figure 3.32). Nonetheless, erosion in established urbanareas can still be seen on steep or poorly vegetatedroadside embankments, on unlined channel banks, and onthe downstream side of some culverts and floodways.

Q U E S T I O N B L O C K 3 E

1. What is soil erosion?

2. How can human activity increase normal erosion?

3. What is the difference between the two types of watererosion?

4. Explain why soil degradation is of concern to farmers.

5. How does the removal of vegetation affect soil erosion?

6. How can soil degradation be minimised in farming areas?

7. Explain why soil degradation is particularly a problem inAfrica.

8. Giving reasons, how successful do you expect AGRA to bein addressing the problems of soil degradation in Africa?Before answering this question, you should check forinformation updates at the AGRA website, which is athttp://www.agra-alliance.org/.

9. How does construction in urban areas affect soil erosion?Explain why this is so.

Water and Change

Water Resource Management

Of the earths surface, 70% is covered by water. Of thiswater, 97% is contained in oceans as salt water, and is

therefore not usable for drinking or irrigation. Of theremaining 3 % that is freshwater, only 0.3 % is found inrivers and lakes, the rest being frozen. It is easy tounderstand why water is regarded as a scarce resource inmany parts of the world.

The result is that water must be conserved and usedefficiently. Therefore, the need to manage water arises is aresponse to matching the supply of water to people withtheir domestic and industrial needs needs such such ashousehold use, manufacturing, irrigation, recreation andnavigation (figure 3.33)

3.33 Water is a very scarce resource in arid areas. Irrigation, usingunderground supplies from oases, is often necessary to enable foodcultivation necessary to feed human populations. This aqueductsupplies water to a small community in the Dra Valley in Morocco,near Zagora at the western edge of the Sahara Desert. Thetransformation of the oases can be seen by comparing the aridsurrounds in the background.

Humans cannot survive for more than a few days withoutwater. Therefore, it must be argued that water is one of

the most precious resources in the world for humans. Formany people, however, access to clean drinking water is amajor problem more people die each day from drinkingwater than drinking alcohol, and over one billion of theworlds population do not have access to safe drinkingwater (figure 3.34).

Access to safe drinking wateris a major concern, and it isaddressed in one of the targets of the MillenniumDevelopment Goals (MDGs) discussed in chapter 2.Specifically, the MDG is to halve the proportion of peoplewithout sustainable access to safe drinking water and

basic sanitation by 2015. In looking at the factors thataffect access to safe drinking water, it is important tounderstand what is meant by the terminology:




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Drinking wateris water that is used for domesticpurposes, including drinking, cooking and personalhygiene;

Accessto drinking water means that the source of wateris less than 1 kilometre away from the place where itwill be used, and it is possible to obtain at least 20 litresper member of a household per day on a reliable basis;

Safedrinking water is water with bacterial, chemicaland physical characteristics that meet World HealthOrganisation (WHO) guidelines or national standardsfor drinking water quality.

3.34 A majority of the worlds population does not have access to cleandrinking water. In this view, a boy collects water from a heavilysedimented pond in the village of Minnanthu in central Myanmar.

Putting these three definitions together, access to safedrinking wateris measured as the proportion of peopleusing improved drinking water sources, which includeshousehold connections (such as piped water), publicstandpipes, bore hole, protected dug wells, protectedsprings or rainwater (figure 3.35).

The problem with using unclean water is that there is ahigh risk of disease. Among the common water-bornediseases are diarrhoea, cholera, schistosomiasis andintestinal problems such as hookworm and hepatitis.About 1.6 million die each year from diarrhoea and

cholera that were caught from unclean water supplies,while 6 million are visually impaired from schistosomiasisand 133 million suffer from intestinal infections caughtfrom unsafe water.

The need to manage water is becoming more pressing asdemand increases. Figure 3.36 shows the amount of wa-ter used in various regions of the world in 1995 comparedwith projections for 2025. In 1995 the world used 3,906cubic kilometres (km3) of water. By 2025, water use formost uses (domestic, industrial, and livestock raising) isprojected to increase by at least 50%. This significant

increase will severely limit the water available for use inirrigation, which will increase by just 4%, restrictingincreases in food production in some parts of the world.

3.35 Drawing water from a well in Djenn, Mali.

Although the world has abundant supplies of water, thesesupplies are unevenly distributed, both within and amongcountries. In some areas of the world, water use isgrowing so rapidly that surface stores are being depletedand even underground reserves are shrinking morerapidly than they can be replenished. One-third of theworlds population live in countries that are experiencingmoderate to high stress on their water supplies, whichmeans that their consumption levels exceed 20% of theavailable supply.

It is expected that this situation will become worse in thedecades ahead as the demand for water increases. TheUnited Nations estimates that by the year 2025, two-thirdsof the worlds population will live in countries that areexperiencing moderate to high stress on their watersupplies. Much of the additional demand for water isexpected to come from manufacturing, and if presenttrends of growth in manufacturing continue, globalindustrial water use will double between 2000 and 2025.Globally, agriculture accounts for 70% of water use, and

the use of water for this purpose is expected to increasebetween 50% and 100% over the same period.


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3.36 Total water use by region, 1995 and 2025.Source: International Food Policy Research Institute

As shown in figure 3.36, much of the increase in demandfor water will occur in the developing countries (LEDCs)as population growth and industrial growth is expected tobe most rapid in those countries. This is important be-cause it highlights the difference between physical waterscarcity and economic water scarcity. Physical waterscarcityoccurs in places where the demand for water ex-ceeds the supply. Physical water scarcity is most commonin arid and semi-arid areas where rainfall is low and riverflow fluctuates, perhaps even drying up at certain times ofthe year. Economic water scarcity, on the other hand,

occurs when water is available but some people cannotafford to obtain it for reasons of poverty. Economic waterscarcity is most common in LEDCs, especially among theurban poor living in shanty settlements in the cities.

3.37 Water pollution aggravates local water shortages because it makesthe water unusable for other purposes. In this view, a man defecatesinto an already heavily polluted open canal in Jakarta, Indonesia.

When water is used, it often becomes polluted. Waterpollution adds to the problem of scarcity of water becauseit removes additional volumes from the availab

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