Chapter 2 climate

Chapter 2: Variable Weather and Changing Climate – A Continuing Challenge

An Introduction

Key Questions of Chapter

1. Why do different places experience different weather and climate?

2. What is happening to the Earth’s climate?


Gateway 1: Why do different places experience different weather and climate?

Section Objectives

Weather vs. Climate

Elements of Weather

Climatic types: Characteristics & Location

Gateway 1: Why do different places experience different weather and climate?

What is the difference between weather and climate?

• Condition of the atmosphere at a particular place and timeWeather

• The average condition of the atmosphere of a specific place over a long period of time – usually over 30 years

Climate

What are the elements of weather?

QUESTION: How would you describe today’s weather?

Warm?

No rain?

Humid?

Windy?

Cloudy?

What are the elements of weather? Weather

Temperature

Relative humidity

Clouds

Rainfall

Pressure & winds

1) Temperature

• The degree of hotness or coldness Ener

gy of

sun

Travels

through the atmosphere

Absorbed by the earth’s

surface

Warms up

Heats up

atmosphere

1) Temperature

• Measured in degrees Celsius (⁰C)• Important terms:–Maximum and minimum temperature–Diurnal temperature range–Mean daily/monthly/annual temperature–Annual temperature range

Maximum and minimum temp.

• The highest and lowest temperatures recorded within a day.

• Normally affected most by the presence or absence of sunlight (key heatsource)

Diurnal Temperature Range

• The difference between the Maximum and minimum temperature of the day.

January 1 2 3 4 5 6 7 8 9 10 11 12Maximum 26 27 27 26 28 28 28 28 29 29 27 25Minimum 25 25 25 24 25 25 24 25 25 26 26 24

QN: What is the diurnal temperature range for 9 January?

Mean Annual Temperature

• The average of all the monthly average temperatures

• Method 1: Sum of all divided by 12 months.

• Method 2: Sum of highest and lowest months divided by 2

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecCOUNTRY C -30 -28 -25 -20 -16 -15 -10 -16 -22 -29 -30 -35COUNTRY D 27 27 28 28 29 30 32 30 30 29 28 28

Annual Temperature Range

• The variation of temperature between the monthly average temperature readings.

• Difference between the maximum and minimum mean monthly temperatures in a year.

QN: What is the annual temperature range for Country C?

Why and how does temperature vary over different areas?

Factors affecting the temperature of locations

Latitude Altitude

Distance from the sea

Cloud cover

Factors affecting temp: Latitude

• Refers to the imaginary horizontal lines running east to west around the earth

• Equator = 0⁰• North / South Pole = 90⁰N / 90⁰S• Angle of incidence: the angle at which the

sun’s rays hit the earth surface

Factors affecting temp: LatitudeLow AOI:

lower temperatures

• Sun’s rays strike at a lower angle

• Solar energy is spread out over a wider area

• Sun’s rays strike at a higher angle

• Solar energy is concentrated on a small area

High AOI: higher

temperatures

Food for thought: the earth tilts at 23.5⁰ results in some places not receiving sunlight for months. How is this so?

Video: 30 days of night

http://www.youtube.com/watch?v=GxC0Um9zSqY



Factors affecting temp: Altitude

• Refers to the height of a location in relation to the sea level

Factors affecting temp: Altitude (TB p. 76)

• The ___ the altitude, the ___ the temperature• Temperature decreases with altitude

WHY?!

Factors affecting temp: AltitudeReason 1• Atmosphere is mostly heated by the earth’s

surface

Shortwave radiation

Longwave radiation

The higher up the atmosphere you go, the further you are from the source of heat (earth’s surface) lower temperature.

Factors affecting temp: AltitudeReason 2• Air is less dense at

higher altitudes • The lower the

altitudes, the higher the density of the air

• Dense air is able to absorb more heat from LW radiation higher temperatures at lower altitudes

QUESTION: What are the gases that absorb heat?

Fun Fact 101: How altitude affects baking

Factors affecting temp: Distance from the sea



• The sea heats up and cools down more slowly than the land difference in rate of heating & cooling between coastal and inland areas difference in temperature –Maritime vs.

Continental effect


Maritime effect • The effect of large ocean bodies on climate of

coastal areas• During summer the air over the sea remains cooler

than the land as it heats up slower• During winter the air over the sea remains warmer

than the land as it loses heat slower• This causes coastal areas to have cooler summers

and warmer winters• The annual temperature range is thus smaller


Continental effect• The effect of continental surfaces on climate of

inland areas• Inland areas are further from the sea and oceans• These areas are not influenced by the

temperatures over the sea• Inland areas tend to have warmer summers and

colder winters• The annual temperature range is thus larger

TB p. 77

Factors affecting temp: Cloud cover

• Refers to the extent of sky that is covered by clouds

• More cloud cover results in a smaller diurnal range

• Less cloud cover results in a larger diurnal range

• This is due to the effect of clouds absorbing and reflecting the sun’s rays and heat energy from the earth’s surface

TB p. 77

Qn: Why do different places along the same latitude have different

temperatures?

http://drought.unl.edu/DroughtBasics/WhatisClimatology/ClimographsforSelectedInternationalCities.aspx




Homework: PITSTOP 2 (TB p. 79)Questions 1, 3 & 6


Temperature

Relative humidity

Clouds

Rainfall

Pressure & winds

2) Relative humidity

• Refers to the ratio between the actual amount of water vapour and the maximum amount of water vapour that the air can hold at a given temperature

• Formula: x 100

EXERCISE: if the air at 15⁰C holds 5g/m³ of water vapour and can contain a maximum of 10g/m³ of water vapour, what is its relative humidity?

2) Relative humidity

• Relative humidity varies with temperature• Warmer air can hold more water vapour• If temperature rises and the actual amount of

water vapour remains, then relative humidity will __________

TB p. 80, Figure 2.14

2) Relative humidity – Key terms

• Saturation is when relative humidity = 100%• Dew point temperature: temperature

at which saturation occurs• Condensation occurs during dew point

temperature


Temperature

Relative humidity

Clouds

Rainfall

Pressure & winds

3) Clouds• Refer to visible masses of water droplets or ice crystals

suspended in the atmosphere• When the earth’s surface is heated up…1. Evaporation: water becoming water vapour2. When water vapour rises, it cools to dew point

temperature3. Condensation: water vapour changes to liquid form4. To condense, water vapour needs to find

condensation nuclei 5. Coalescence: water droplets bumping into each other

to become larger in size

At dew point temperature

• video

4) Rainfall

• Precipitation refers to water that falls from the atmosphere to the earth surface in any form

• E.g. hail, snow, sleet, rain • In the tropics, precipitation is mainly rain• Measured using a rain gauge

4) Rainfall

• Rainfall is caused by air instability when an air parcel is warmer than its surrounding air, causing it expand (becomes less dense) and rise

• Qn: What is air stability?• Air stability: a parcel of air that is cooler than

its surrounding air and tends to sink and remain in its original position

• 2 types of rainfall: Convectional and Relief

4) RainfallConvectional• Occurs due to intense heating of earth’s surface• Warm surface heats the air above it• Instability causes air to rise and expand• As air rises, it cools to dew point temperature• Condensation occurs and clouds are formed• When water droplets become large enough, they fall as

rain• Convectional rain is often associated with lightning and

thunder• Intense rain over a short amount of time


4) RainfallRelief• Also known as Orographic rain• As air passes over the sea, it picks up moisture• When it arrives at the coast, moist air is forced to rise along

the windward side of the mountain• Air is forced to cool and condensation occurs at dew point

temperature• When water droplets in the clouds become heavy enough

they fall to the ground on the windward side• On the other side of the mountain, leeward side, it is dry as

most of the moisture is lost on the windward side (rain shadow)

Video: Formation of Relief Rain

http://www.youtube.com/watch?v=kTc_uS3i9Ps

http://www.youtube.com/watch?v=kTc_uS3i9Ps


Qn1: Based on your own experience with the weather in Singapore, what type of rain do

you think we experience dominantly?

Qn2: Explain why the other form of rain is not common here.

Homework: PITSTOP 3 (TB p. 82)Questions 1, 2, 3 and 5


Temperature

Relative humidity

Clouds

Rainfall

Pressure & winds

5) Pressure and winds

• Air pressure: the forced exerted by the weight a column of air on a unit area of the earth’s surface

• Measured in millibars (mb) by a barometer• Air is less dense at higher altitudes• Thus air pressure decreases as altitude

increases• The average value of air pressure at sea level

is 1,013mb

Air pressure is higher at sea level and lower at higher altitudes


• Wind: The movement of air from high pressure area to low pressure area

• Pressure gradient: The difference in air pressure between two places

• The greater the pressure gradient, the faster the wind speed

• Wind can be described by its speed, direction and frequency.


Wind speed• The rate at which air is moving• Measured in kilometres per hour, using an

anemometer• Wind speed may also be represented by the

Beaufort Scale (TB p. 85, figure 2.23)


Wind direction• The direction which the wind blows from• Measured by a wind vaneWind frequency• The percentage of time the wind blows from a

particular direction• Winds that blow most frequently from a specific

direction prevailing winds• Information of wind direction and frequency can

be recorded using wind roses

Wind vane

Wind rose

5) Pressure and winds – Wind systems

• Prevailing winds can be categorised by wind systems Wind systems

Localised Land breeze

Sea breeze

RegionalMonsoon Winds

Mid-latitude Westerlies

Polar Easterlies

Localised wind systems

Land breeze and sea breeze• Occur in coastal areas due to different rates of

heating between the land and sea• Recall: maritime effect• Lowers the temperature of coastal areas

during the day and regulate the temperature during the night smaller diurnal temperature range

Localised wind systemsLand breeze• Blows from the land to the sea• In the night:–Sea loses heat slower resulting in warm air

above the sea rises up, leaving a vacuum (Low pressure)–Land loses heat/cools down faster than the

sea (High pressure)–Cooler air above the land rushes towards the

sea as land breeze

TB p. 86, Figure 2.24a

Localised wind systems

Sea breeze• Blows from the sea to the land • In the day:– Land heats up faster than the sea warm air

above the land rises up, leaving a vacuum (Low pressure)

– Sea heats up slower than the sea cooler (High pressure)

– Cooler air from the sea rushes towards the land as sea breeze

TB p. 86, Figure 2.24b

5) Pressure and winds – Wind systemsWind systems

Localised

Land breeze

Sea breeze

Regional

Monsoon Winds

Mid-latitude Westerlies

Polar Easterlies

Regional wind systems

Monsoon winds• A regional wind pattern• Brings seasonal changes in precipitation• Affected by Coriolis effect (a force produced by the

earth’s rotation)• Northern hemisphere deflects to the right• Southern hemisphere deflects to the left• Coriolis effect is stronger nearer the poles and weaker

near the equator• Winds result in monsoons (SW & NE monsoons)

Take a moment to digest…

• You should keep the following background knowledge that you ALREADY HAVE…– Summer = Higher Temp, Winter = Lower Temp– High Temp = Low pressure, Low Temp = High

pressure– Concept of relief rain and rain shadow– Coriolis Effect: North = Right and South = Left

• For purpose of study, we will use the monsoon winds blowing between Asia and Australia as an example


Southwest monsoon (TB p. 88, figure 2.26)• June to September• Summer in northern hemisphere, winter in

southern hemisphere• Winds move from Australia (south) to Asia (north)• From Australia, wind moves as southeast monsoon• As it crosses the equator, it deflects to become

southwest monsoon• The air picks up moisture over Indian Ocean and

brings heavy rain to India

The Southwest monsoons in summer in the northern hemisphere


Northeast monsoon (TB p. 88, figure 2.27)• October to February• Summer in southern hemisphere, winter in

northern hemisphere• Winds move from Asia (north) to Australia (south)• From Asia, wind moves as northeast monsoon• As it crosses the equator, it deflects to become

northwest monsoon• The air picks up moisture over Indian Ocean and

brings heavy rain to Australia

The Northeast monsoons in winter in the northern hemisphere

Qn: How does the NE and SW monsoon winds affect Singapore in

terms of rainfall?

Homework: PITSTOP 4 (TB p. 80)Questions 2 and 4

Section ObjectivesWeather vs. Climate

Elements of weather

Climatic types: Characteristics & Location

KGQ 1: Why do different places experience different weather and climate?

What are the climatic types and where are they experienced? (TB p. 91)

Climatic types

Equatorial Monsoon Cool temperate

Warm temperate Dry Other cool

temperate

Polar Highlands

Climatic type: Equatorial• Between 10⁰ north and south of the Equator

Characteristics/features Explanation

Temp. • High temp (Mean annual temp of about 27⁰C)

• Small annual temp range of 2⁰C to 3⁰C

• High angle of incidence of the sun’s rays

Relative humidity (RH)

• High RH • High temp warmer air able to hold more water vapour high RH

Rainfall (RF)

• Convectional rain often occurs

• Rain throughout the year with no distinct wet or dry seasons

• Total annual RF: more than 2,000 millimetres

• High temp intense heating of earth’s surface instability convectional rain


Case study: Weather and climate of Singapore

• Equatorial climate– Uniformly high

temperature– Abundant rainfall– High relative humidity

• WHY???– Located at a latitude of

1⁰22’N-(Latitude, cloud cover, High humidity)

Climatic type: Monsoon• Between 5⁰ and 25⁰ north and south of the

Equator (e.g. Chittagong in Bangladesh)

Characteristics/features Explanation

Temp. • High mean annual temp.• Overall lower mean annual

temp than equatorial climate• Mean monthly temp about

30⁰C in May but about 25⁰C in July

• Annual temp range is about 6⁰C

• Located further from the equator as compared to equatorial regions

Rainfall (RF)

• Distinct wet and dry seasons• Concentrated RF in the summer

(June – Sept) • E.g. Chittagong receives 2,000

mm of RF during the wet seasons (June – Sept) and only about 75 mm of RF during the dry season (Oct – May)

• Monsoon winds


Climatic type: Cool temperate (marine west-coast) climate

• Between 45⁰and 60⁰ north and south of the equator (e.g. Paris in France & Toronto in Canada)

• Four distinct seasons (spring, summer, autumn & winter) due to tilt of the earth and revolution around the sun

Characteristics Explanation

Temp. • Large annual range of 25⁰C (temps ranging between -3⁰C and 22⁰C

• During winter shorter days less energy from the sun

Rainfall (RF)

• Evenly distributed throughout the year

• However, total annual RF is lower than in places with the equatorial or monsoon climate

• Total annual RF ranges between 300 mm and 900 mm.

• No distinct wet or dry seasons


Homework: PITSTOP 5 (TB p. 93)Questions 1, 2 and 4

KGQ 2: What is happening to the Earth’s climate?


CHECK-IN: Icebergs on the loose

102

1 2

3

Section ObjectivesHow has global climate changed

Natural causes of climate change

Human causes of climate change – enhanced greenhouse effect

Impacts of climate change

Responses to climate change

Global climate change

• Refers to the variation in the global climate or climatic patterns in the long term

• Happening since the 1800s significant but irregular temperature increases (0.3⁰C – 0.6⁰C)

1980 – 2000: rose by 0.4⁰C in 20 years!

Observation 1: The global temperatures are increasing

Observation 2: The global temperatures are irregular (they increase and decrease)

Global warming and cooling

• Refers to the climatic changes due to natural cycles as observed over hundreds to millions of years

• Global warming: the increase in global temperatures over a long period of time

• Global cooling: the decrease in global temperatures over a long period of time


Changes in global climate since 1881

http://www.youtube.com/watch?v=9kFHQpZpgdg



Changes in global climate since 1881

• The earth has warmed by an average of 0.74⁰C over the last century

• Greatest increases after the 1980s• The warmest temperatures recorded so far are

between 1990 and 2015

What are the causes of climate change?

Causes of climate change

Natural Human

What are the natural causes of climate change?

Natural causes of climate

change

Variations in solar output

Volcanic eruptions

Natural causes of climate change: Variations in solar output

• The amount of solar radiation the sun emits depends on any changes in its Magnetic field

Magnetic activity

Solar Radiation

Solar activity cycle: 11 years

High Magnetic Energy

Low Magnetic Energy


• Sunspots: cooler areas on the sun’s surface that appear as dark spots

• Sunspot areas—about 4000 degrees Celsius• Other areas—about 5000 degrees Celsius


Sunspots• Sunspot activity is linked to the amount of

solar radiation emitted• E.g. During high solar activity, there are more

sunspots as the areas surrounding the sunspots release more magnetic energy compensates for the lower temperatures

• E.g.

What are the natural causes of climate change?

Natural causes of climate

change

Variations in solar output

Volcanic eruptions

Natural causes of climate change: Volcanic eruptions

http://www.youtube.com/watch?v=WecgO8cBcZY



Mount Pinatubo, Philippines (1991)

Mount Pinatubo, Philippines (1991)


• When a volcano erupts, carbon dioxide, water vapour, sulphur dioxide, dust and ash are released into the atmosphere

• Sulphur dioxide + water = sulphur-based particles reflects solar energy back into space (together with dust and ash) Global dimming

WaterSulphur dioxide Sulphur-based particles

Ash Dust

GLOBAL DIMMING

Dimming?


Global dimming• The gradual reduction in the

amount of sunlight reach the Earth’s surface.

• Cools the Earth for months or years.

• Dips in global temperatures occurred in the 1940s and 1960s because of volcanic activity

Case study: Mount Pinatubo, Philippines (1991)

• The eruption released 17 million tonnes of SO2 spread of sulphur based particles

• Lowered temperatures in the northern hemisphere by as much as 0.6⁰C

• Effects lasted for two years (temporary)

Qn: How long do the effects of volcanic eruptions last? Why?

Ans: They are temporary! The temporary global cooling effect will cease once the volcanic dust and ash settle.

Homework: PITSTOP 6 (TB p. 101)Questions 1, 2, 3 and 4

Section ObjectivesHow has global climate changed





What is greenhouse effect and how does it work?

http://www.youtube.com/watch?v=ZzCA60WnoMk


• Natural process in which the gases in the Earth’s atmosphere trap longwave radiation emitted from the earth’s surface, warming the atmosphere.

What is greenhouse effect and how does it work? (TB p. 102, Fig 2.49)


Greenhouse gases (GHG)

Water vapour

Carbon dioxide

Methane

Nitrous oxide

Ozone

Halocarbons

What is the enhanced greenhouse effect?

• The increase in the amount of greenhouse gases in Earth’s atmosphere due to human activity

Anthropogenic factors


Homework: PITSTOP 7 (TB p. 103)Questions 1 & 2

How do human activities lead to the Enhanced Greenhouse Effect?

Burning fossil fuels

Deforestation Changing land use

▪ Agriculture▪ Industries

▪ Urbanisation

Burning Fossil Fuels

• Formed from dead organic matter that has been decomposed over many millions of years

• E.g. oil, coal and natural gas• Burnt to produce a large

amount of energy important for human activities (e.g. transportation, industries, domestic)


• Estimated to produce more than 80% of • Large consumers: China, USA, Canada and UK• In Singapore, most of our electricity is

generated by fossil fuels


• Fossil fuels contribute to an increase in GHG • High carbon content produce large amounts of

carbon dioxide when burnt highest contributor of GHG

• World’s usage of fossil fuels has increased in recent years releases billions of tonnes of carbon dioxide into the atmosphere each year

• 2010: global CO2 emssions = 30.6 billion tonnes (5.6% increase from 2009)






▪ Urbanisation

Deforestation

• The loss of forests due to the removal of trees in forested areas– Wood paper and building materials– Clearing of land for human activities e.g. mining,

grazing of animals and planting of crops (agriculture), construction of infrastructure

How does deforestation result in enhanced greenhouse effect?

• Deforestation fewer trees to absorb CO2 increase in CO2 levels in the atmosphere greenhouse effect

Forests are absorbers of

carbon dioxide (through

photosynthesis)

• Deforestation soil exposed to sunlight increase rate of carbon oxidation of soil increase in CO2 levels greenhouse effect

Soil is one of the largest sources of

carbon in the world

How does deforestation result in enhanced greenhouse effect?


Deforestation

• 52,000 km² of forest lost every year between 2000 and 2010 (142.5 km² lost every year)

• Great overall loss of forests occurs in S. America, Southeast Asia, Australia and Africa WHY? The need for development: agricultural and commercial activities (e.g. cattle ranching)





▪ Urbanisation

Changing land use

Agriculture• The practice of

cultivating land, producing crops and raising livestock

How does rice cultivation and padi fields contribute to the increase of greenhouse gases in

the atmosphere?

Tractors run on fossil fuels which release CO2Use of inorganic

fertillisers increase amount of nitrous oxide in soil released when soil is ploughed or when rain flows through it

Organic matter such as dead leaves releases methane during decomposition

How does cattle farming increase greenhouse gases in the atmosphere?

Cattle release methane as a waste gas!!!

Changing land use

Industries• The production of

goods and services within a country• Secondary industries

(manufacturing) involve the burning of fossil fuels GHG as by-products

Changing land use

Processes emitting carbon dioxide

Process Kg of CO2 equivalent

Equivalent activity

a) Manufacturing a mobile phone

60 A car travelling 7 times the length of the PIE in Singapore

b) Manufacturing a computer and a monitor

275 A car travelling 31 times the length of the PIE in Singapore


Changing land use

Urbanisation• Process by which an increasing number of

people live in urban areas (i.e. cities or towns)

How does urbanisation increase greenhouse gases in the atmosphere?

How does urbanisation increase greenhouse gases in the atmosphere?

Urbanisation

• Urbanisation: Process by which an increasing number of people live in urban areas.

159

- Various human activities are concentrated or are necessary in urban places. All of them contribute to the amount of greenhouse gases in the atmosphere.

Homework: PITSTOP 8 (TB p. 108)Questions 1 & 2

How has global climate changed





How does climate change affect people?


Sea level riseFrequent extreme

weather events

Spread of infectious insect-borne diseases

Lengthening the growing season in

certain regions

Impacts of Climate change

Sea level rise• Increase in mean height of the sea’s surface• Causes:– Higher temperatures melting of glaciers in

Greenland and Antarctica addition of meltwater rise in sea level

– Higher temperatures water in seas expand rise in sea level


Sea level rise• Negative impact on places where humans live• Threatens low-lying areas, coastal areas and

islands – Over 600 million people live in areas less than 10

metres above sea level – 33% of coastal land and wetland habitat are

predicted to be lost in the next 100 years

TB p. 110 Figure 2.61


More frequent extreme weather events• Extreme weather event: a

severe and rare weather phenomenon that results in significant losses

• E.g. heat waves, floods, droughts and tropical cyclones


More frequent extreme weather events• Causes:–Higher temperatures greater amounts of

water vapour and latent heat in a warmer atmosphere driving force for extreme weather events


Spread of infectious insect-borne diseases• Increased temperatures and

rainfall favourable condition for insects to thrive spread of insect-borne diseases– Climate change results in diseases

occurring in cool climate areas as well• E.g. heavy rainfall allowing

mosquitoes to grow in aquatic habitats DENGUE fever & MALARIA


Lengthening the growing season in certain areas• Growing season: period during which crops can

be grown• Lengthened growing seasons affect different

crops differently (+ve or –ve)


Lengthening the growing season in certain areasAdvantages Disadvantages

In the United Kingdom, the types of crops that can be grown increased. E.g. Blackberries and maize.

In the Yunnan Province, China, the production of fruits such as apples and cherries, and nuts such as almonds and walnuts is reduced as these fruits and nuts require cool weather conditions.

The production of fruit, soybeans and potatoes is projected to increase in Canada.

In Canada, the average wheat grain yield has reduced.

Homework: PITSTOP 9 (TB p. 112)Questions 1, 2 & 4

Section Objectives

How has global climate changed





What are the responses to climate change?Responses

International level

Kyoto protocol

Copenhagen Conference

National level

Case study: Singapore (e.g. Singapore Green Plan)

Case study: India (e.g. National Urban Transport Policy)

Responses at the international level

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Chapter 2 climate

Education