human impact

• Greenhouse effect:

  During the day, radiation is reflected by the Earth and atmosphere, or absorbed by the Earth's surface which warms. At night, some infrared radiation passes through the atmosphere but most is absorbed and re-emitted in all directions by greenhouse gas molecules, which warms the Earth's surface and atmosphere.
• Water vapour:

  • 36% for clear sky
  • 66% for clouds
  • 9 days residence time
  • amplifies the effects of other gases
• Carbon Dioxide:

  • 400 ppm
  • from burning fossil fuels, and deforestation
  • 62 years residence time
• Methane:

  • 1800 ppb
  • bacteria, bogs, landfill sites, guts of cattle
  • 12 year residence time
  • 25 more contributing than CO2
• Chlorofluorocarbons (CFCs):

  • 1863 ppt
  • old aerosols and refrigerators
  • up to 50 000 year residence time (variable)
  • efficient absorber of long wave radiation
• Urban heat island effect is when there are higher temperatures in urban areas than neighbouring rural areas.
• In cities, the sun's energy is absorbed by buildings, so the air is heated by buildings. This forms cumulus clouds as air rises, which causes convectional rain. There's more clouds as there's lots of dust which act as condensation nuclei.
• Urban wind is when wind is funnelled by tall buildings, so the wind can be 2-3 times stronger. There is a Canyon effect between tall buildings.
• High temperatures in urban areas:

  • high absorption of solar radiation e.g. concrete
  • car engines/exhausts
  • buildings with central heating or air conditioning
  • factories
  • greater surface area as walls and roofs create more space
  • parks decrease temperatures
• Ocean salinity is changing due to global warming. The poles have fresher water due to glacier melt and increased rainfall. The equator has saltier water due to increased evaporation. This will stop the Great Ocean Conveyor Belt, changing temperatures around the globe.
• Global warming is causing the ice caps to melt at a rate of 2.4% per decade.
• The sea levels are rising by 3.1 mm a year due to melting glaciers and thermal expansion, which is when water expands as it warms.
• The acidity of oceans have increased by 26% since 1750, changing the pH from 8.2 to 8.1, due to CO2 dissolving in the water to form carbonic acid.
• Biological indicators of global warming:

  • bee-eaters are found in the UK
  • malaria is increasing in southern Europe
  • bleaching of coral reefs due to increased acidity of oceans