Weather hazards and climate change (Atmospheric circulation (The main idea…
Weather hazards and climate change
The main idea is the Hadley cells
Intense heating at the equator means that air rises. As it does so it cools, condenses and it rains either side of the equator - rainforests produced.
Air moves towards the poles, cools and sinks. Sinks around 30 degrees North and South.
Sinking air – permanent high pressure created and this creates deserts.
Also Ferrel Cells and Polar Cells – see diagram.
Air moves from high pressure to low pressure – along the surface of the earth – known as trade winds (key for tropical storm).
Jet streams - fast moving bands of air in the upper atmosphere.
They can move weather systems around the world.
There are warm and cold ocean currents
They move around the world re-distributing heat.
Main one for the UK is the North Atlantic Drift – this keeps the UK warmer than places at comparable latitude. E.g. UK is much warmer than parts of Canada in winter at the same latitude.
Quaternary period and Natural causes of climate change
3 causes of natural climate change
Sun spots (solar variation) - These dark patches on the sun. When there are more of these, Then temperatures on earth are higher
Volcanism - Volcanic eruptions emit Sulphur Dioxide - This reacts with water in the atmosphere to form sulphuric acid. This is an aerosol and reflects energy back from the sun. Ash also blocks out sunlight.
Milankovitch cycle - 3 cycles
Eccentricity – This is where the earth’s orbit varies from circular to elliptical and back again – takes around 100,000 years. Means that when the earth is furthest from the sun – colder temperatures – glacial period.
Precession – this is where the earth axis wobbles and this can ‘push’ the earth further away from the sun. When this happens – cooler periods on earth.
Axial tilt – When the earth’s axis is at a larger angle the earth is further away from the sun and colder temperatures found on earth.
These have changed climate over the Quaternary period which is the last 1.6 million years.
Evidence of Climate change in the past
Ice cores: taken from polar regions. Tell us about past climates. Ice is in layers – the thickness of the layer provides information on the amount of precipitation that fell in a year. Gas is trapped in bubbles in the ice – the amount of Co2 tells us whether it was a glacial period or interglacial. More CO2 in the ice during a glacial period. Pollen is trapped in the ice – more pollen in ice means temperatures were likely to be warmer/wetter.
Pollen records – pollen comes from plants – these grow more during interglacial periods when temperature/rainfall is greater.
Tree rings - width of the tree rings indicates the amount of growth of the tree that year
Human causes of climate change
Farming activities - these produce more methane e.g. more cows for greater demand for beef. Methane is around 30 times more effective at trapping heat when compared to carbon dioxide and so this is a big issue.
Tree Rings – width of the tree rings indicates the amount of growth of the tree that year.
Impacts of climate change – rising sea levels, changing patterns of crop production, retreating glaciers
Rising sea levels
Melting of ice which contributes to higher sea levels – melting of ice on Antarctica is significant for this as the ice is not currently taking up any space in the sea.
Thermal expansion which is where the sea is at a higher temperature and so takes up more volume and so sea level rises.
Due to higher temperatures some plants may not grow as effectively - may impact food supply.
Photosynthesis is not as effective at higher temperatures.
Problems of water supply in some regions e.g. Himalayas. Ice melting also adds to sea level rise as the water flows to the sea.
Variations in temperature and rainfall
Temperature warmer in the South, colder in the North. Due to latitude.
Air masses – 4 air masses influence the UK and these determine the weather that the UK gets.
Variations in rainfall – due to relief rainfall – Mountains on the West of the UK.
Rain shadow on the East of the UK.
Tropical Storm – Characteristics, Hazards and Formation
Only form in certain locations – source areas. They need the following:
Sea needs to be 27(degrees Celsius)
Winds converging at the surface – the trade winds
Around 8-20 degrees north/south (latitude) of the equator. There needs to be sufficient distance from the equator in order for the Coriolis force to have some impact. This provides the spin for a tropical storm.
Above 20 degrees north or south (latitude) - the sea is too cold for a storm to form
Low wind shear - Winds cannot vary much with height otherwise the storm won't form.
High winds – can produce flying debris which acts as a further hazard
Intense rainfall – flooding and landslides
Storm surges – Most deadly hazard – wall of water being washed inland due to strong winds.
Causes of drought
Meteorological – A lower than average amount of rainfall in an area.
Hydrological – Lower levels of stored water e.g. in reservoirs which is caused by a lack of rainfall. However, this lower level of stored water will mean less water in rivers.
Dams – Less water available downstream
Deforestation – Less transpiration and so less rainfall
Agriculture – Too much water removed from water sources for irrigation and so less water in rivers.
Why is drought a hazard
People are forced to use lower quality water sources which means the spread of water borne disease is more likely
Fires and dust storms are more likely
People able to produce less food and so famine and malnutrition more common