Hazardous Earth

• the atmosphere transfers heat around the earth in a global circulation system which creates areas of high and low pressure explaininv why the earth has areas with high rainfall (low pressure) and arid areas (high pressure)
• Uv heat energy from dun is most intense at equator, powering a huge circle of air movement called a circulation cell. Hot air rises 15km at the equator creating low pressure, the air cools and travels N and S of the equator 30° where it sinks creating high pressure. where cells meet, energy is transferred
• rising air at the equator (under lower pressure) cannot hold as much moisture, so precipitation is higher at the equator. Cooler air falling at 30° of latitude creates high pressure with clear skies and little precipitation. This is why these areas are often arid.
• 3. Ocean currents also transfer heat around the globe. Some are powered by wind resulting from circulation cells. Other are powered by differences in water temperature and salinity.
• Asteroids hitting the Earth can cause huge fires that release large amounts of Carbon dioxide which has a warming effect.
• Climate change has happened due to natural causes many times in the Earth's history, on timescales ranging from hundreds to millions of years.
• These are long-term temperature changes.
• We can obtain data about temperature changes from ice cores.
• Ice cores are cylinders of ice obtained by drilling through glaciers of ice up to 500000 years old.
• Asteroid collisions can cause cooling, as material blocks the Sun.
• The Earth's orbit changes a small amount once every 100 000 years, called a Milankovitch cycle.
• Volcanic eruptions pump ash into the atmosphere, which has a cooling effect.
• Ocean current changes can cause cooling and warming.
• The amount of energy radiated by the Sun changes over an 11-year cycle.
• When UV rays from the Sun reach the Earth's atmosphere, the land and oceans absorb the heat and radiate infrared heat back into the atmosphere.
• Greenhouse gases in the atmosphere trap some of the heat.
• Human activity, including industry, transport, energy production and farming, increases greenhouse gases, leading to more warming.
• Evidence of how human activity is causing climate change includes sea levels rising, global temperatures rising, Arctic ice declining and extreme weather events becoming more frequent.
• Because natural events are hard to predict and the atmosphere and oceans are highly complex systems, projections for future changes may not be accurate.
• Possible consequences of global warming include more destruction from more frequent extreme weather events, more coastal flooding from rising sea levels, and changes in farming which could affect food supplies.
• Low Pressure - warm, moist air rises through the atmosphere, sucking more air behind it
• Rotation - the Earth's spin helps the rising air to spiral and drags in strong winds.
• Structure-tropical cyclones form a cylinder of rising, spiralling air around an eye of descending, high-pressure air.
• Tropical cyclones occur in the tropics, starting between 5° and 30° of latitude
• Tropical cyclones only form where seawater is above 26.5°C, so they happen in summer and late autumn when the seawater is warmest.
• Tropical cyclones start in the tropics and move westward, because winds blow from the east around the equator.
• Some tropical cyclones reach a belt of winds blowing from the west, which makes them change direction.
• Tropical cyclones can travel 600km in a day.
• Global circulation

  Heat being most intense at the equator causes the air above the earth to get hot, hot air rises causing low pressure, warm air rises cools condenses forms rain, low pressure means rainfall, hot air spreads out either side of the equator, drops back down over the tropics causing high pressure, high pressure leads to dry conditions
• ITCZ (Inter Tropical Convergence Zone)


  A band of rain at the equator that moves due to the Earth's rotation around the sun and its tilt, causing rainy seasons in regions like West Africa
• Hadley cell


  A circulation model where hot air rises at the equator, cools, condenses, spreads out, drops back down, and rises again, causing wet conditions at the equator and dry conditions on either side
• Ferrel cell


  Another circulation model where warm air rises, causes low pressure, leads to rainfall, spreads out, drops back down, and some of it goes towards the poles
• Global circulation cell includes the Hadley cell and the polar cell
• Ocean currents move heat through the water from the equator to the poles
• Reasons for West African rainy season

  • Tilt of the Earth
  • Movement around the sun
• High pressure deserts

  • Hadley cell (tropics)
  • Polar cell (poles)
• Warm air rises, condenses, drops, spreads out, and drops back down


  Forms the Hadley cell, some goes up to the North Pole, drops back down causing high pressure, forms the polar cell
• Rain falls in areas of low pressure
• Pressure systems

  • Hadley cell
  • Polar cell
• Air always moves from high pressure to low pressure