2.3 - environmental threats to our planet

2.3.1

definition of the quaternary period

• covers the last 2.6million years

• often called - ice age - due to Antarctica

2.3.1

explain the climate change from the beginning of quaternary period to now

• temperatures fluctuated wildly

• overall gradually cooled

• cold spikes = glacial episodes - ice age

• now = interglacial episode

• average temp today - higher than most of quaternary period

2.3.1

explain medieval warming period

• lasted from 950 to 1250AD

• some regions - temp equals today

• overall temp = lower than today

2.3.1

explain little ice age

• following the medieval warming period

• 1300 - 1870

• europe and north america = colder winters

• rivers + seas around UK froze

2.3.1

explain modern warming

• todays’ temperature increasing

• compared to average temp in 20th century - increased in last few decades

2.3.1

main evidence for climate change

• increase of average surface air temp by 1’C - last 100 years

• warmest ocean temp since 1850

• average rise in sea levels - 20cm since 1900

2.3.1

evidence for climate change - global temperature data

• over 1000 ground weather stations + satellite info → map global temp

• increased by 0.6’C by 1950

• LIMITATION - weather station - not evenly distributed (Africa) - reliable?

• data - only till 1880

2.3.1

evidence for climate change - ice cores

• oxygen, CO₂ and methane = found in ice cores

• estimate past temp = 800,000 years

• compare to present level

• scienctists - drill deep into ice in Antarctic + Greenland - extract thousand year old ice

• reliable

2.3.1

evidence for climate change - tree rings

• one tree ring = year of growth

• narrow rings = cool + dry past climate conditions

• wider rings = warmer + wetter past climate conditions

2.3.1

evidence for climate change - paintings + diaries

• suggest evidence of climate change through observations

• price increases in grain in Europe

• sea ice - prevent landing in Iceland

• people - emigrating - crop failure

• winter ‘Frost Fair’ - frozen River Thames

• art = much colder winter landcspes - 17th century

• cave paintings - draw animals - 11,000 + 40,000 years ago

• subjective and hard to date

2.3.2

explain how variations in energy from sun caused climate change

• sunspots = dark patches on sun’s surface

• caused by outburst of magnetic energy

• scientists - more sunspots = more heat is given off by Sun

• BUT - solar output = barely changed - cannot be responsible for climate change from 1970

2.3.2

explain how changes in the earth’s orbit caused climate change

distribution of sun’s energy = varies due to change in earth’s orbit.

• Axial tilt - spins on tilted axis

  • angle of tilt changes - gravitational pull from moon

  • angle of tilt - large = higher average temp

• Precession - ‘wobble’

  • as the earth spins during its rotations - it wobbles

• Eccentricity - earths orbit around sun

  • not fixed + changes over time

  • almost circular to slightly elliptical

  • cold period = circular

  • warm period = elliptical

2.3.2

explain how volcanic activity caused climate change

• huge quantities of ash, gas + liquid → into atmosphere

• sulphur dioxide + water vapour = volcanic aerosol

• this reflects sunlight away - reduces global temp

• wind - carries material far away - reduced temp experienced somewhere else

2.3.2

what is natural greenhouse effect

• natural occurring phenomenen

• keeps Earth warm enough for life to exist

1. sun’s infrared heat rays - enter Earth’s atmosphere

2. heat - reflected from Earths surface

3. natural layer of atmosphere + greenhouse gases = some heat is trapped + some heat reflected

2.3.2

what is enhanced greenhouse effect

• natural causes = not responsible for current rise in temp

• human activity = cause

• increased layer of greenhouse gases - 77% CO2, 14% methane, 8% NOs, 1% CFCs

• less of sun’s energy = escape atmosphere - temp increases

2.3.2

name some human activities that contribute to enhanced greenhouse effect

• CO2 - burning fossil fuels, deforestation

• Methane - cattle rearing, rice paddy fields, decomposition in landfill

• NOs - exhaust fumes, agriculture + industrial processes

2.3.3 - global
social impact of sea level rise

• 600 million people = live coastal areas - 10m above sea

• environmental refugees - increase due to flooding

• migration + overcrowding - low risk areas - Asia

2.3.3 - global
economic impact of sea level rise

• agricultural land - lost to sea - Bangladesh

• world cities - affected - global finacial hubs - London + New York

• transport infrastructure - destroyed

• investment in coastal defences - increased pressure from sea level rise

• tourism - loss in income - beaches = flooded/eroded

2.3.3 - global
environmental impact of sea level rise

• 33% - coastal land + wetlands - lost in 100 years

• bleaching in coral reefs - loss of biodiversity

• mangrove forests - natural barrier - destroyed in storms

• fresh water sources polluted - salty seawater

2.3.3 - global
social impact of extreme weather events

• drought - affect farm + water supplies

• diseases - skin cancers + heatrstoke - temp increase

• winter deaths decrease - winters become milder

2.3.3 - global
economic impact of extreme weather events

• increase into investment - prediction + protection

• repair + damage costs - $9.7 billion in 2010 pakistan

• crop yields - decrease - 12% in South America - trade

2.3.3 - global
environmental impact of extreme weather events

• Forests = forest fires, more pests, disease

• food shortages - animals such as oranguatans

• flooding south asia - increase rice yields

2.3.4 - main climate regions

Polar

LATITUDE - poles 90’N + S of equator

Characteristic:

• cold air from polar cell - sinks → high pressure

• spin of earth - dry, icy winds

2.3.4 - main climate regions

Temperate

LATITUDE - 50-60’N + S of equator

Characteristic:

• two air cells meet - one warm from Ferrel + one cold from Polar

• low pressure = created

• warm air meets cold air along a weather front

• frequent rainfall

• UK

2.3.4 - main climate regions

Subtropical

LATITUDE - 30’N + S of equator

Characteristic:

• Hadley + Ferrel cells meet = high pressure

• belt of desserts - Sahara

• daytime temp = more than 40’C

2.3.4 - main climate regions

Tropical

LATITUDE - at equator - 0’

Characteristic:

• Hadley cells meet - belt of low pressure

• air rises rapidly

• regular heavy rainfall + thunderstorms

• Malaysia - south east asia

2.3.4

how does global circulation work

• three large scale circular movement of air = cells

• act in each hemisphere

• take air from Equator - move it towards the poles

2.3.4

explain Hadley Cell

largest cells

• where - equator to 30’ N and S

• How - wind meets near equator - warm air rises = thunderstorms

• drier air flows out towards 30’N - before sinking over subtropical areas

2.3.4

explain Ferell cell

middle cell

• where - edge of hadley cell - 30’ to 60’ N + S

• how -

  • air in this cells joins the sinking air from Hadley

  • travels across mid-latitude regions

  • until air rises along the border of cold air with polar cell

2.3.4

explain polar cell

smallest + weakest cell

• where - edge of ferrel cell to poles at 90’

• how

  • air sinks over higher latitudes at poles

  • flows towards mid-latitudes

  • where it meets with ferrel cell and rises

2.3.4
what does high pressure cause

• air cools - denser and falls towards the ground → high pressure

• cool air warms - as it reaches earth’s surface

• cause clouds to evaporate

• heavy rain at equator = most moisture gone by time air reaches subtropics

• clear skies, dry hot weather

2.3.4
what does low pressure cause

• causes warm air to rise → cools + condenses = clouds

• precipitation occurs = rain, sleet etc

• day + night = similar temp because cloud cover reflects solar radiation during day and traps it at night

2.3.4 - explain
extreme weather conditions around the world

temperature

coldest place

• Vostok, Antarctica

• -89.2’C

• height of 3500 m

only polar cells exist here - cold air sinks - producing high pressure

causes dry icy winds - spin of earth

very cold - the sunlight does not concentrate here

polar climate

2.3.4
extreme weather conditions around the world

temperature

hottest place

• Libya

• 57.8’C

• 32’N of equator

desert climate

hadley + ferrel cells meet => high pressure due to sinking dry air

2.3.4
extreme weather conditions around the world

precipitation

driest place

• Aswan Egypt - average rainfall - 0.861mm er year

• close to tropic of cancer

hadley + ferrel cells meet => high pressure → sinking dry air

high pressure - surface level

2.3.4
extreme weather conditions around the world

precipitation

wettest place

• puerto lopez - annual rainfall = 13m

  equator

  rising air in hadley = rises, cools, condenses = rain

  low pressure - at surface level

2.3.4
extreme weather conditions around the world

windiest place

• commonwealth bay - Antarctica

• exceed 240km/hour

• average annual = 80km/hour

polar climate - polar cells

storms = katabatic winds - carry air from high ground due to gravity

NEW ZEALAND:

polar and ferrel cells meet at 60’S - rising air - low pressure

space left is fill by westerly winds + the easterlies coming from the poles

2.3.5

what happens during a normal weather event?

• trade winds over Pacific push warms waters towards western pacific - australia

• warm air rises - over coast of australia

• cools + condenses = rainfall

• east pacific = air descends = high pressure

• colder water - near surface bc warm water moves west

• good conditions for fishing

2.3.5

what happens during the el nino weather event

• trade winds weaken, stop or reverse in west pacific

• accumulated water in australia - moves back towards east pacific → 30cm sea level rise in peru

• prevents cold water from rising + reduces fish stocks

• increase in water temp in peru - rising warm water, low pressure, more rainfall → risk of flood

• descending air over australia - high pressure dominates - stable, dry conditions → droughts

2.3.5

what happens during the la nina weather event

• happens usually after el nino

• more exaggerated version of normal event

• australia - flooding

• sea temp - cold around peru

2.3.5

what are tropical storms

• low-pressure system in tropics

• with winds - move in a spiral around a central point (eye of the storm)

• winds = powerful

• rain = heavy

• develop into tropical cyclone

2.3.5

where do tropical storms occur

• 5 & 15’N and S of equator

• temp of ocean surface = more than 26.5’C

• ocean depth = 50-60m

• 500km away from equator - coriolis effect can make weather system rotate

2.3.5

explain some causes of tropical storms

LOW LATITUDE - 5 - 30’N, S of Equator

• temperatures - higher here - air is heated more quickly, rises = low pressure system

• Coriolis effect - system can rotate and spin

OCEAN TEMP = 26.5’C - depth - 60m

• provides heat + moisture - warm air rises rapidly

LOW WIND SHEAR

• wind is constant, so clouds can rise to high altitudes without being torn apart

2.3.5

explain the formation of tropical storms

1. Air = heated above the surface warm tropical oceans → rises rapidly under low-pressure conditions

2. rising air draws up more airing large volumes of moisture from the ocean = strong winds. 

3. Coriolis effect → the air to spin upwards around a calm central eye of the storm. 

4. As the air rises, it cools and condenses to form large, towering cumulonimbus clouds = generate heavy rainfall

5. Heat is given off = the air cools + powers the tropical storm. 

6. Cool air sinks into the eye → there is no cloud → drier, clear and much calmer. 

7. tropical storm travels across the ocean bc of prevailing wind. 

8. When the tropical storm meets land = no longer fuelled by the source of the moisture and heat from the ocean → loses power and weakens.

2.3.5

frequency of tropical storms over time

• 80 per year

• most powerful = western pacific

• june to nov - northern hemisphere

• nov to april - southern hemisphere

• energy released by hurricane - increased by 70% in last 30yrs

• during el nino = less hurricanes in atlantic, more tropical cyclone in east of south pacific

2.3.5

what are droughts

• prolonged period of time - unusually low rainfall

• not enough rainfall to support people or crops

2.3.5

where do droughts occur

• sahel region of Africa

• middle east - affected by war + conflict

• regions that are already dry - australia, parts of us, china

2.3.5

what is intertropical convergence belt

• low pressure belt - encircles the earth around equator

• where the trade winds from northeast and southeast meet

• earth tilts - cause ICTZ to migrate between tropics of cancer + capricorn

2.3.5

physical factors that cause drought

• dry, high-pressure weather system

• el nino = descending air + high pressure over Australasia → drought

• global temp increase - more water is lost from surface by evaporation

• ITCZ may not move s far north/south as usual - depriving regions (africa) of rainfall

2.3.5

human factors that cause droughts

• excessive irrigation

• deforestation - reducing transpiration

• overgrazing - exposing soil to wind erosion

• dam building - regions downstream of water

• intensive farming

2.3.5

frequency of droughts over time

• met office predicts - extrme drought once in decade for UK

• 2013 report from NASA - warmer global temp = less rainfall , more droughts

2.3.6 - case study

intro for drought in australia

• 2002 - 2009

• worst drought in 125 years

• big dry

2.3.6 - case study

causes for the drought in australia

• geographical location - subtropical area - experiences dry, sinking air → clear skies + little rain

• 2006 - rainfall - 40-60% below normal - over most of Australia south - Tropic of Capricorn

• el nino - rainfall decrease - drier than normal

• murray-darling river basin = 2 million people - lot of pressure to supply water to residents + agricultural

2.3.6 - case study

social consequences of drought in australia

• People in rural areas with a lack of water and opportunity move to the cities, putting greater pressure on the population of cities.

• Rural suicide rates soared, especially among young men.

2.3.6 - case study

responses to drought in australia

INDIVIDUAL

• recycling waste water - shower, bath

• farmer - claim financial assistance for $400-$600 per fortnight

LOCAL GOV

• subsidising rainwater - storage tank for home

• legislation to ban car washing + limit showers to 4 min

NATIONAL GOV

• multimillion-dollar desalination plant built in Sydney

• paying out 1.7 mill a day in drought relief to farmer

SCIENTISTS + ENVIRONMENTALIST

• more efficient irrigation system

• calculating sustainable amount of water - to create a limit that could be traded across states

2.3.6 - case study

economic consequences of drought in australia

Farmers sold cattle and sheep as they could not afford to feed them. 50% of dairy farms were lost.

Food prices rose as Australia became more dependent on imports.

Water bills rose 20% in 2008.

Tourism was negatively affected.

10,000 people directly employed by the cotton-growing industry were affected as the crop failed.

The number of dairy farms reduced by more than half.

2.3.6 - case study

environmental consequences of drought in australia

• Loss of vegetation, wildlife and biodiversity. Drought is killing eucalyptus trees, which are the main source of food for koalas so this affected koala numbers as well. 

• Soil erosion. As the soil dries out, it becomes looser and it is easier for the wind to blow it away with knock-on effects on soil fertility and ecosystems. Grassland turned to scrubland. 

• Devastating bush fires as the dry vegetation burns easily and there is little water to put fires out. This destroys wildlife habitat and may have killed millions of animals. 

• Energy from HEP was reduced leading to more air pollution as Australia resorted to the use of fossil fuels. 

• Water quality reduced as toxic algal outbreaks occurred in depleted rivers, dams and lakes.