the atmosphere

composition of the atmosphere

nitrogen = 78

oxygen 21

co2 = 0.04

rare gases = 1

ozone = 0.000007

how the atmosphere supports life

dynamic equilibrium = natural processes are in a state of balance which maintains the average composition of the atmosphere so that it only changes over very long timescales

gases for natural processes - needed to make biological molecules used by living organisms

absorption of electromagnetic radiation from the sun - most of the UV rays that pass through the upper atmosphere is prevented from reaching the earths surface by various forms of oxygen present in the stratosphere
gases absorb UV light - producing a dynamic equilibrium of chemic reactions which form and destroy ozone

1 oxygen - monatomic

3 oxygen - triatomic

delaying the escape of infrared energy - incoming visible light is absorbed, converted to heat, and re-emitted as infrared energy. occurring atmospheric gases absorb this infrared energy, convert it to heat and increase the temp of earth

heat distribution - most energy from the sun, absorbed at the earths surface, is absorbed in tropical regions - warm surface heats the atmosphere above and this heat is distributed to high latitudes by warm winds

ocean currents - wind blowing over oceans create currents that distribute heat by carrying warm water from tropical areas to higher latitudes

transport of water vapour - winds transport water vapour to areas that would otherwise get little or no precipitation

atmospheric pressure - controls the ease with which water molecules can evaporate and escape from the water surface, if atmospheric pressure was much lower there would be no liquid water on earth

altitude - affects the composition and physical features of the atmosphere resulting in a series of layers, of which the troposphere and the stratosphere are the most significant . is is these layers that are affected by human activities

2 oxygen - diatomic

human activities = anthropogenic changes

natural greenhouse effect

atmospheric processes that warm the troposphere

visible light passes through the atmosphere easily and is absorbed by the earth surface which warms it up

warm earths surface emits infrared radiation which cannot pass through the atmosphere as easily as visible light because it is absorbed by gases in the atmosphere (the greenhouse gases)

greenhouses gases are any gases that are better at absorbing infrared than the average for the atmosphere

the most important natural greenhouse gases are co2 and water vapour

if there was no natural greenhouse effect, the mean temp of earths surface would be 33 degree colder

enhanced greenhouse effect and global climate change

co2 - combustion - ploughing- 1 relative effects

methane - anaerobic respiration - formation of fossil fuels and released by ventilation of coalmines

oxides of nitrogen - oxygen and nitrogen from the air react at high temp in locations such as vehicle engines and power stations - fertiliser use

chlorofluorocarbons (CFC's) - aerosol - fire extinguishers - refrigerants

tropospheric ozone - photochemical breakdown of NO2 and subsequent reactions of oxygen

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ecological changes due to climate change

species - temp change affect species they rely on or changes to natural processes

plants - temp rise plants grow faster = more food for herbivores such as butterflies

precipitation changes may cause wetland habitats to enlarge or shrink

deep root trees (oak trees) able to survive in droughts better than shallow roots (beech trees)

dormouse hibernation may be disturbed by warmer winters, causing them to use up stored fat - starvation

timing of ecological events such as flowering, migration and nesting may change

distribution of species may change as conditions have changed and they colonise areas that have become more suitable