Global Climate Change

Topic 5: Global Climate Change Scientific evidence shows that our climate is changing is not hard to find – there have been major climatic changes throughout the earth’s history. The graph below shows the last 150 years in detail.

Causes of Global Warming Physical Causes: These causes have always been here and have been responsible for the periodic heating and cooling of the earth’s temperature. – Volcanic eruptions release huge amounts of gas into the atmosphere therefore more scattering takes place of the insolation. The most marked example is the global cooling, which took place after the Krakatoa eruption of – Cycles of sun spot activity appear to increase temperature when there are more sunspots. – Orbital variations – wobble, tilt and roll theory suggests that the tilt and orbit of the earth vary slightly in cycles but these are very long term changes (possibly leading to ice ages) and unlikely to cause short term changes. – Over a long period of time oceanic alteration and/or continental drift can cause climate change

Causes of Global Warming Human Causes:

Causes of Global Warming Human Causes: These causes have increased in the last years. Greenhouse gases such as CO 2, CFCs and methane absorb terrestrial radiation and hold onto it for longer than other gases. The more of these gases in our atmosphere – the warmer it will become. – CO 2 is the least dangerous – but exists in the largest quantity and has been increasing due to: the industrial revolution which saw dramatic increases in the burning of fossil fuels such as oil and gas. the deforestation of the rainforests and their subsequent burning. the lack of trees reduces the amount of CO 2 recycled into O 2.

Causes of Global Warming Methane – expelled from the digestive system of cattle – which are increasing to cope with world population increase. – emitted from padi fields during rice cultivation – again to cope with the demand for food. Rice is a staple crop grown in south and East Asia – where population is growing the fastest. – Produced from fossil fuel exploration. – Emitted from landfill sites – a fast growing land-use in MEDCs due to the consumer society. – Emitted from natural wetlands – which will increase as the Artic tundra melts – catch 22.

Causes of Global Warming Chlorofluorocarbons (CFCs) are the most dangerous greenhouse gas. They are produced by: – Fridges – Aerosols

Causes of Global Warming Although legislation in many MEDCs has reduced their production, they are still produced by LEDCs who cannot afford new technology. All of these contribute to The Greenhouse Effect – heat is trapped in the Earth’s atmosphere causing a rise in temperature. War may cause a slight lowering of global temperature as smoke released into the atmosphere from bombing can cause a fall in temperature.

Possible Consequences of Global Warming Melting of the ice sheets/glaciers A rise in sea level with subsequent migration as islands and coastal areas are submerged. Loss of plant and animal habitats in these areas e.g. impact on polar bears which could lead to a loss of tourism/more problems in settlements as the bears scavenge instead of hunting on the ice. New transportation routes across the Arctic Ocean i.e. the North West Passage with resulting benefits to trade in previously ice bound coastal settlements. Extension of mineral exploitation into the Arctic with positive and negative consequences.

Possible Consequences of Global Warming Changing rainfall/temperature patterns Higher or lower rainfall/temperature and maybe more extreme weather depending on where you are with resulting increasing/decreasing crop yields, more floods/drought/hurricanes/tornadoes etc. Extension or retreat of vegetation (and associated wildlife) by altitude as well as latitude – growing vines/sunflowers in Scotland, spread of malaria, the loss of the Cairngorm Arctic habitat etc. Change in ocean currents (El Nino/La Nina). Change to the Atlantic Conveyor – disruption of the thermohaline circulation.

Possible Consequences of Global Warming