What causes anticyclones to form?

1. Rossby waves (as they turn away from poles).2. Dense, cool air in winter over large continental areas.3. Semi permanent areas of high pressure associated with the global atmospheric circulation e.g. subtropical high pressure zone.

• The ‘heat equator’ is the region of the Earth directly underneath the sun.• The heat equator receives the most amount solar energy.• The heat equator migrates between the tropics of cancer and capricorn.

• As the heat equator migrates, so does the zone and period of heaviest rainfall.

Short term climate change

Short term climate change operates over periods of up to a 1000 years. El Niño is an example of very short-term widespread climatic disruption.

Key words:• El Niño - a warm ocean current that occurs in the eastern Pacific off the coast of Peru in December. It occurs with a periodicity of 3-7 years and has a huge impact on the world’s normal weather systems.

• La Niña - colder than average sea surface temperatures in the central and eastern equatorial Pacific. La Niña usually occurs just before or just after El Niño.

• Southern oscillation - the see-saw like change (switch) in atmospheric pressure over the eastern and western equatorial Pacific regions.

• ENSO - (El Niño-southern oscillation) the tern used to refer to the full range of events, i.e. both the changes in the ocean temperature and atmospheric circulation.

• Teleconnections - the link between climate and weather systems over large distances.

• Thermocline - the sharp and deep

boundary between cold, deep ocean water

and a warmer upper layer.

How does the ENSO work? A normal year.

How does the ENSO work? An El Niño year.

How does the ENSO work? A La Niña year.

Global Warming: TRUE or FALSE

1. Gases in the Earth’s atmosphere keep the Earth warm by absorbing longwave radiation leaving the Earth’s surface. This naturally occurring effect is called the greenhouse effect.

2. Without the Greenhouse effect the Earth would be about 10 °C colder.

3. The main greenhouse gases are: carbon dioxide, methane, helium and nitrogen oxide.

TRUE

FALSE

FALSE

4. The concentration of greenhouse gases has decreased over the last 100 years.

5. The Earth’s average temperature has increased by about 0.5 °C over the last 100 years due to an enhanced greenhouse effect.

6. The main causes of global warming are an increase in transportation by vehicles, greater use of electricity by homes and industry and clearing forests for farming.

FALSE

TRUE

TRUE

7. The Earth’s climate does not change naturally.

8. Global warming will increase the number of extreme weather events like floods and hurricanes.

9. Global warming will cause sea-level to fall because warmer temperatures mean more evaporation of water from the sea.

10. Global warming will cause ecosystems and habitats to move towards the poles.

FALSE

TRUE

FALSE

TRUE

• Short term climate change operates over periods up to 1000 years.

• An example of short term climate change is the current global warming.

• The greenhouse effect is the natural mechanism by which some of the heat escaping from the Earth’s surface as long-wave radiation is absorbed and reflected back to Earth by certain gases in the atmosphere.

Global Warming

• The enhanced greenhouse effect is the impact of people increasing the greenhouse effect by human activities, notably the use of fossil fuels and deforestation.

• Global warming is the consequence of an enhanced greenhouse effect. The planet will continue to warm until a new equilibrium is reached between the input of energy from the sun and the heat lost by Earth into space.

Thenaturalgreenhouseeffect

Theenhancedgreenhouseeffect