topic 6- environmental threats to our planet - Coggle Diagram
topic 6- environmental threats to our planet
global circulation of the atmosphere
There are three large-scale circular movements of air in each hemisphere of the Earth’s surface.
Hemisphere- northern an southern halves split by the equator, eastern and western split by lines of latitude.
These circular movements, or ‘cells’, take air from the Equator and move it towards the poles.
The cells have a role to play in creating the climate zones on Earth.
The cells are:
The largest cell
Extends from the Equator to 30°North and South
Winds meet near the Equator and the warm air rises, causing thunderstorms
The drier air then flows out towards 30°, before sinking over subtropical areas
The middle cell
From the edge of the Hadley cell at 30°to 60°in the North and South
Air in this cell joins the air at the edge of the Hadley cell
It travels across mid-latitude regions until the air rises along the border of cold air with the Polar cell
The smallest and weakest cell
Occurs from the edge of the Ferrel cell to the poles at 90°
The air sinks over higher latitudes at the poles and flows towards the mid-latitudes
The air then meets the Ferrel cell and rises
Atmospheric air pressure
Low pressure is created where two Hadley cells meet and air rises. (air raising warms up = low pressure on surface)
Low pressure causes warm air to rise, then it cools and condenses forming clouds.
Moisture falls from the atmosphere as rain, sleet, snow or hail (precipitation).
Same temp day and night as the cloud cover reflects solar radiation during the day and traps it at night.
High pressure is created where Hadley and Ferrel cells meet and the air descends.(air sinking cools = high pressure on surface)
air cools becoming denser as it moves towards the surface causing high pressure.
heavy rainfall at the equator means the clouds are moisture less when they reach the subtropics.
high pressure causes clear skies and dry hot weather.
Trade winds- winds which blow from the tropical regions towards the equator. usually travel in an Easterly direction
main climate zones of the world
At the poles 90°North and South of the Equator
cold air from the polar cell sinks at the poles producing high pressure. dry icy winds from the spin of the earth. In Antarctica.
Mid-latitudes 50°to 60°North and South of the Equator
warm Ferrel cell and cold Polar cell meet going up. low pressure created as cold and warm meet at a weather front. frequent rainfall ie in the UK
30°North and South of the Equator
Hadley and Ferrel cells meet sinking. creates dry clear weather like in the Sahara in North Africa and Namib in south Africa. temperature exceeds 40 degrees.
At the Equator,0°line of latitude
low pressure where Hadley cells meet and air rises. regular heavy rainfall and thunderstorms. ie Malaysia- south east Asia and Northern Brazil in South America.
extreme weather conditions- natural weather hazards
El Nino weather
it was once thought to be caused by the sea floor heating up from volcanic activity, however this is unlikely.
They may be caused by small changes in sea temperature
The most likely cause is tropical storms which trigger the water to move in a different direction to normal
Temperatures cool very quickly making tall clouds from high amounts of condensation.
winds near the ocean surface blowing from different directions joining up and causing air to rise and storm clouds to form
Arrival of warm, moist air from tropical oceans with sea surface temperatures being quite warm.
winds are similar height and speed - known as low wind shear. This allows the storm clouds to rise vertically to high levels.
water vapour from warm water forms heavy, low clouds
The winds reach the top of the
where they are deflected outwards by the
effect making the storm rotate.
Troposphere- a certain height in the atmosphere about 16km high where weather takes place
Coriolis effect- effect of the earths rotation on weather and ocean currents- makes southern hemisphere storms turn clockwise and northern hemisphere storms turn anticlockwise.
Trade winds weaken, stop or even reverse in the western Pacific.
Higher sea levels normally found in Australia move over towards the eastern pacific- reduces the normally high fish stocks in Peru.
Increased water temperatures in Peru, leading to warm air, low pressure and high rainfall- increased risk of flooding.
High pressure in Australia as air descends, dryness can lead to droughts.
La Nina often happens after an El Nino event, it is a more exaggerated version of a normal year.
Australia can experience flooding
Sea temperatures are cold around Peru
trade winds over pacific push warm water to the west, near Australia
warm air raises over warm water in Eastern Australia, Then cools bringing rainfall.
In the Eastern pacific, near Peru air descends causing high pressure. Surface water is cold,
an area of low pressure with powerful winds spiraling around a clam central eye, heavy rainfall too.
come from the tropics and develop into cyclones when winds reach 119 km/h
known as hurricanes or typhoons in different areas
found around the equator although at least 500km away so that Coriolis effect can take place
prolonged period of low rainfall, can't support people or crops.
They occur in arid (dry) climates with low levels of rainfall- Australia and USA (California).
The most droughts occur around the tropics of Capricorn and Cancer and the Equator
Physical causes of droughts
Dry, high pressure climate/ weather
El Nino events bringing high pressure
Increasing global temperatures- water lost from surfaces
Intertropical convergence zone may not move as far as usual one season depriving regions of rainfall.
ITCZ- low- pressure belt around equator where trade winds from Northeast and Southeast meet. the earth is tilted when orbiting the sun causing it to move between tropic of cancer and Capricorn with the seasons. woowww that was a long explanation.
Human causes of droughts
Too much irrigation as water from supplies is used for crops and runs out and intensive farming too.
Deforestation reduces transpiration therefore rain
Overgrazing, exposing soil to wind erosion
Dam building- deprives regions downstream of water
Frequency of Tropical storms
Most powerful and frequent ones occur in western pacific
occur from June to November in northern hemisphere and November till April in the southern Hemisphere
energy released by hurricanes over last 30yrs has increased lots
In El Nino there are fewer hurricanes in the Atlantic and more tropical cyclones in the eastern part of the South Pacific
scientists don't think climate change effects tropical storms
CASE STUDY- Drought In Australia
What caused it?
From 2002 to 2009, Australia had worst drought in many years- in the south- east mainly.
It was caused by El Nino event
Australia has changeable rainfall patterns and its geography allows it to dry up easily
Australia is located in a sub-tropical area with dry sinking air leading to clear skies and little rain.
When El Nino is in action chances of rainfall decrease becoming drier especially in the East.
Trade winds over Pacific Ocean (normally bring warm water) weaken, water cools and rainfall stops
Causes for stress
Australia cannot give enough access to water with its growing population.
Murray- Darling river basin - Eastern Australia- home to 2 million people with not enough water for residents and agriculture.
What were the consequences?
people left rural areas due to lack of water, increased pressure on cities.
Streams dried up- birds and fish lost habitat and food supply decreased.
Increased use of fossil fuels as HEP energy was reduced- more pollution.
soil erosion and loss of vegetation
Grasslands turned to scrub land
Food prices rose and Australia became more reliant on imports
Cattle had to be sold, and cotton growing industry left a lot of people with no jobs
Tourism at Murray area decreased
Water bills rose 20% in 2008
number of dairy farms reduced by half
What were the responses?
recycled waste water
farmers claimed financial assistance per a fortnight
provided rainwater storage tanks for homes
received legislation to ban car washing and limit showers to 4 minuets.
Built a new multi- million de-salination system in Sydney
payed out $1.7 million a day drought relief to farmers
Scientists and environmentalists
found more efficient irrigation systems
calculated the amount of water that could be used sustainably by a state to create a limit.
Climate change from the start of the Quaternary period
Climate changes from the start of the Quaternary period
Climate change since 1000AD
It was followed by the 'Little Ice Age' from 1300 to 1870. Rivers and seas around the UK froze.
In comparison to temperatures from 1901-2000, average global temperatures have increased.
The Medieval Warming Period lasted from 950 to 1250AD. Where overall temperatures were lower than today.
Periods of warming and cooling since 1000AD.
Evidence for climate change
Scientists drill deep in the ice (in Antarctic/GL) to extract ice that is thousands of years old.
Data is considered reliable.
Oxygen, carbon dioxide & methane in ice cores can help estimate past temperatures by comparing it to present levels.
Narrow rings indicate coloer drier past climate conditions.
Wider rings indicate warmer and wetter past climate conditions.
Each tree ring present a year of growth.
Global temperature data
But weather station are not evenly distributed, especially Africa, so reliability is questioned.
Computer programmes used to produce global temperature maps don't make them reliable & data only goes back to 1880
Average global temperature have increased by 0.6oC since 1950 & 0.85 since 1880.
NASA use over 1000 ground weather station and satellite information to map global temperature.
Painting and diaries
Artist captured cold winter landscapes in Europe and North America in the 17th century.
Cave paintings of animals in France and Spain drawn between 11,000 and 40,000 year ago show significant climate change.
Price increase in grain in Europe - Sea ice preventing ships from landing in Iceland - People emigrating due to crop failures - Winter 'Frost Fairs' held on the frozen River Thames.
It is difficult to date cave painting accurately and personal accounts are art are subjective viewpoints.
Diaries and written observations can suggest evidence of climate change at the time.
Since 1914, Met Office have recorded reliable climate change data - using weather stations, satellites, weather balloons, radar and ocean buoys.
They have found - an increase in air temperature by 1oC over the last 100 years, the warmest ocean temperatures since 1850, an average rise in sea levels of 20 cm since 1900.
Climate changes since the Quaternary period
Climate change during quaternary period
There have been cold 'spikes'/glacial episodes. In between each spike there is a warmer inter-glacial episode.
We live in an inter-glacial episode with temperature higher than in most of the Quaternary period.
Temperatures have fluctuated, overall gradually cooled.
Climate change in the last 400,000 years.
Glacial episodes last approx. 100,000 years; thick ice expands, covering vast areas.
Temperatures have remained stable and warmer for longer
Inter-glacial episode last approx. 10,000 years.
Often called the ice age
A period of time that stretches' from 2.6 million years ago to today is called the Quaternary period.
Climate change - changes in long term temperature and precipitation patterns that can natural or linked to humans.
Inter-glacial episodes - historic warm periods between glacial periods.
Ice age - glacial episode characterised by lower than average global temperatures and ice covered most of the earth surface.
Causes of climate change
Human activity contributing to global warming
Enhanced greenhouse effect
Thicker layer of green house gases means less of Suns energy is able to escape earths atmosphere, so temp increases more.
Scientists proved natural causes are responsible but they cant account for change in temperature.
Natural layer of greenhouse gas
Some heat trapped
Some heat reflected some trapped
Less heat able to escape.
Earths temp increases
Thicker layer of greenhouse gases.
Emitted from livestock & rice cultivation
Decay of organic waste in landfills
Agricultural and industrial processes
Burning fossil fuels (oil, gas, coal)
Suns infrared rays enter earths atmosphere.
Heat reflected from earths atmosphere.
Natural layer of greenhouse gases lets heat to reflect but some gets trapped. Keeps earth warm
Naturally occurring phenomenon keeps earth warm enough to exist.
Natural greenhouse effect - natural warming of planet, as some heat reflected by earth absorbed by liquids & gases in atmosphere, (carbon dioxide)
Exaggerated warming of atmosphere cause by human activities, resulting in natural greenhouse effect becoming more effective.
Global warming - a trend associated with climate change involving a warming trend.
Natural causes of climate change
Changes in the earths orbit
Earth spins on titled axis, & the angle changes due to the gravitational pull of the Moon.
When the angle tilt is greater, it's associated with a higher average temperature. The angle of tilt moves every 41,000 years.
Earth is not a perfect sphere so it as it spins it wobbles on it axis in a 26,000-year cycle.
Distribution of Suns energy on the Earth varies due to changes in Earth orbit. There are three Milankovitch cycles;
Earths orbit around the Sun isn't fixed & changes over time from being almost circular to mildly elliptical.
Cycle take 100,000 years - Colder periods occur when Earth's orbit is more circular and warmer periods when it is elliptical.
When sulfur dioxide mixes with water vapour it becomes a volcanic aerosol which reflects sunlight away, reducing global temperatures.
Wind carries material beyond where it was ejected so reduces temperatures elsewhere.
Eruptions throw huge quantities of ash, gases and liquids to the atmosphere.
Variation in energy from the sun
Scientists say that the more sunspots there are the more heat is given of by the sun.
But solar output from the sun has not changed much in the last 50 years, so it cant be responsible for the climate change seen since 1970s
Sunspots are caused by magnetic energy inside the sun & they increase from a minimum number to a maximum number in a sunspot cycle of every 11 years.
Sunspot - a spot or dark patch that appears from time to time on the surface of the sun; associated with an outburst of energy from the sun.
Milankovitch cycles; the cycle time periods that relate to the Earth's orbital changes around the sun.
Consequences of climate change
The global impact of climate change
Sea level rise
Transport infrastructure damaged by flood water
Investment in coastal defenses needed as currents one are under pressure
World cities (London) could be affected by flooding
Loss of income from tourisms as beaches eroded; hotel forced to shut.
Valuable agricultural land lost to sea or polluted by salt water.
Increase in environmental refugees due to flooding
Job losses in fishing or tourism so had to learn new skills
600 million in coastal areas less than 10 meters above sea level
Migration and overcrowding in low-risk areas dur to flooding
Mangrove forests, which are natural barriers to storms are damaged.
Fresh water sources polluted by salt water
Biodiversity lost due to damage by storms and bleaching in coral reefs
Adelie penguins may decline as ice retreats
IPCC says 33% of coastal land and wetlands could be lost in 100 years
Extreme weather events
Flood risk increases repair and insurance costs
Maize crop yields decrease up to 12% in South America; increase in northern Europe need more irrigation.
Skiing industry decline in Alps less snow
Increases investment in prediction and protection
Lower rainfall causes food shortages for orange-utans in Borneo
Forests experience more pests, disease and forest fires.
Flooding in South Asia increases rice yields.
Increased risk of diseases; skin cancer, heatstroke
Winter related deaths decrease cause mild winters
Increased drought, affecting farmland and water supplies
The impact of climate change on the UK
Impact on seasonal patterns
Big environmental impacts on behavior of wildlife and plants. Burd migration patterns will shift
Trees and plants will flower earlier. Wildlife could struggle to survive if season don't match up with food supply.
Impact on sea level
Salt marshes may become flooded and eroded; managed retreat could create new ones.
Cliff collapse may increase, houses at risk
Agricultural land may be lost due to managed retreat
Thames barriers need expensive upgrading due to risk of flooding.
Teesside industries on coastal mudflat will be vulnerable it.
Tourism industry affected by eroded beaches
Impact on weather patterns
New crops (oranges, peaches) could be cultivated in southern England.
Agricultural productivity may increase under warmer conditions need more irrigation.
Vegetation and ecosystems move north. Sitka spruce yield may increase in Scotland
Heating costs will reduce
Water shortages will happen
UK's elderly vulnerable during heat waves but suffer less cold-related deaths.
Cairngorms ski resort may be forced to close due to lack of snow. Reduce revenue.
Summer heat lead to growth in tourism in Lake district - more jobs, increased revenue.