Hazardous Earth

• The equator separates the northern hemisphere and the southern hemisphere.
• The equator is a line of latitude.
• High pressure is when cool air sinks as it is more dense. No clouds are formed in high pressure.
• Low pressure is when hot air rises. It causes cloudy wet weather.
• Temperature varies across the globe, this is because different parts of the earth receive different amounts of the sun's energy (solar radiation). The sun's energy received at the equator is very intense because this is where sunlight strikes the earth directly, but is very dispersed at the poles. Therefore, the climate is hot at the equator and cooler at the poles.
• On land, dark surfaces absorb sunlight quickly and heat up. When it heats up, the air above it will rise and clouds will form. In summer, areas of low pressure form over land. The sea reflects some sunlight but will absorb some energy up to 30 m deep. Therefore it takes longer to heat but also longer to cool. In summer, over the sea areas remain cool, so the air will sink. Differences in air pressure will cause air to move, from high to low pressure, creating wind, which moves in a circular motion due to the Earth's rotation.
• The Global Circulation Model (GACM) is a simplified version of how air currents in the atmosphere move, it is used to help explain weather patterns and climactic regions. The Hadley Cell is part of GACM.
• The Inter Tropical Convergence Zone (ITCZ) is a low pressure belt encircling the Earth near the equator. It is a zone of convergence where the trade winds meet, it is a zone where pressures meet.
• In the summer months, the Hadley cell creates low pressure over North Africa and high pressure further south. Wind blows from high pressure to low pressure, taking moisture inland, this causes rainy seasons. In the northern hemisphere, the Hadley cell is stronger in winter, creating low pressure over North Africa, while Southern Africa is enjoying warmer temperatures and low pressure. Trade winds blow from high pressure to low pressure, taking dry air from the Sahara over West Africa and causing its dry season.
• The ITCZ is a band of low pressure. It moves because the thermal equator moves due to the tilt of the earth. In September and March the ICTZ is over the equator, bringing rainfall. Whereas in June it is over North Africa and in December it is over South Africa.
• Climate change is the long term change in the Earth's climate. A change due to the increase in the average atmospheric temperature. Climate is the weather over 30 or more years.
• Evidence of climate change is found through:

  • Tree rings
  • Ice cores
  • Historical evidence
  • Temperature records
• Evidence of climate change includes:

  • tree rings
  • ice cores
  • historical evidence
  • temperature records
• Tree ring evidence for climate change is found as trees form a new ring each year, these rings are thicker in warmer climates. This extends back 5000 years ago for living trees, however can be longer for fossilised rings. This is beneficial because it gives us a global understanding, however the trees are killed process.
• Ice sheets are made up of layers of ice, one layer is formed each year. Scientists can analyse the gases trapped in each layer of a core and can work out what the temperature was, this is known as an ice core and is used as evidence for the existence of climate change. This extends back to the quaternary period (2.6 million years ago). This is beneficial because it is very long term and reliable, however, it is very expensive.
• Historical evidence of climate change can give us information such as the number of days of rain or snow, and dates of harvest. It can also give us visual evidence. This is beneficial because it gives us a visual representation, however it doesn't give us specifics and can be inaccurate. It extends back as long as human existence (5000 years ago, approximately).
• Temperature records are recorded using thermometers, they extend back to the past 150 years. This is beneficial because it completely accurate, however it is a very short record.
• Causes of past climate change include:

  • the sun spot theory
  • asteroid collisions
  • the orbital theory
  • volcanic eruptions
• The Sun Spot Theory

  • Black spots on the sun are the hottest areas where the most solar radiation is released.
  • This causes rises in temperature as the number of sun spots changes, causing more areas with more intense solar radiation emissions.
  • It is a eustatic impact.
• Asteroid collisions cause climate change because when an asteroid hits the earth, the atmosphere changes, dust and particles of debris find their way into the upper atmosphere, this blocks the sun. It can last up to 5 - 10 years. It is an isostatic and eustatic impact.
• The Orbital Theory.

  • The orbital theory causes climate change because the Earth's orbit can be circular or oval shaped and every 100,000 years it switches
  • This causes the tilt of the Earth to change and the axis wobbles
  • When the Earth has an oval shaped circuit, it causes an ice age
  • This is a eustatic impact that lasts 100,000 years
• Volcanic eruptions cause climate change as the volcanic ash released into the atmosphere during an eruption, temporarily block the sun, it also releases sulphur dioxide, causing cooling. This is a short term isostatic impact.
• Interglacial means a warm period.
• Glacial means a cool period.
• The enhanced greenhouse effect is a result of human actions.
• The greenhouse effect is a process that occurs when gases in the Earth's atmosphere trap the Earth's heat.
• The Enhanced Greenhouse Effect is the disruption to the Earth's climate equilibrium caused by increased concentration of greenhouse gases, that have led to an increase in the global average surface temperatures.
• Global temperature is rising. This can lead to ice melting, increased risk of disease and droughts.
• The amounts of ice in the sea are decreasing. This can lead to flooding, risk of extinction and destruction of habitats.
• Extreme weather events are increasing. This can lead to loss of homes and damage to infrastructure.
• The ocean temperature is rising. This can lead to habitat destruction, for example the coral reefs may bleach.
• Sea levels are rising, which can lead to flooding.
• There are three main causes of uncertainty on our fossil fuel usage for the future:

  • we dont know the future population
  • people may change their lifestyles
  • there may be a shift to clean energy, rather than fossil fuels.
• Tropical cyclones are rotating low pressure systems that form over warm tropical waters. They are known as hurricanes, cyclones or typhoons. Tropical cyclones bring: intense rainfall, strong winds and storm surges.
• Cyclones are only found 5 degrees North or South from the equator.
• Tropical cyclones form in tropical areas where high temperatures cause air to rise away from the ocean surface. The rising warm air creates low air pressure at the ocean surface. Winds then converge at the ocean surface and due to the Coriolis effect, the storm begins to spin. Tropical cyclones have seasonal distribution due to needing ocean temperatures at 26.5 degrees Celsius to be able to form. Tropical cyclones move in curved lines and are then tracked to make future predictions. They do not occur at the equator because the Coriolis effect is weak or non-existant.
• For a cyclone to form there needs to be:

  • strong winds
  • large, still, warm water at 26.5 degrees Celsius
  • the Coriolis effect
• The Coriolis effect causes rising air to rotate and is strongest at 5 - 30 degrees Celsius. Not found at the equator.
• The Saffir Simpson Hurricane Wind Scale measures the wind speed of hurricanes. It is measured from 1 to 5.
• The Geographical Information System (GIS) is used to track cyclones.