Causes of global climate change

Energy processes in the atmosphere

• Incoming and outgoing solar energy is in a state of dynamic equilibrium

• Wavelengths of electromagnetic radiation, ultraviolet (UV), visible light and infrared

• This energy drives and controls the climate, ocean currents, hydrological cycle and distribution of species

• Earth is a closed system: energy can come in and out but matter can’t escape or enter

  • open system: energy and matter can’t come and go

  • Isolated: energy and matter can’t escape or enter

Energy budget in the atmosphere

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The natural greenhouse effect

Important atmospheric process that warms troposphere

1) Visible light passes through the atmosphere and is absorbed by the Earths surface which warms up

2) The warm earths surface emits IR radiation which can’t pass through the atmosphere and instead is absorbed by greenhouse gases

Greenhouse gases: gases that are good at absorbing IR, e.g. carbon dioxide, water vapour, methane, oxides of nitrogen, CFCs and tropospheric ozone

• With no NGE, Earth would have a mean temp 33 degrees lower

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Enhanced greenhouse effect

• Changes to the composition of the atmosphere that alter energy processes, the climate and physical/ biological processes they control

• Human activity change: anthropogenic

• Anthropogenic activities are increasing concentration of greenhouse gases

  • Some of these gases naturally occur but humans increase frequency of release

  • Some gases only released by human activities

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Oxides of nitrogen

• Oxygen and nitrogen from the air react at high tempos in locations such as vehicle engine and power stations. Released into atmosphere in exhaust gases. Fertiliser can increase emissions

• Wasn’t present before humans

• Natural sources: lighting, forest fires

• Relative effects per molecule: 160

Carbon dioxide

• Combustion of fossil fuels and wood, ploughing of soils, drainage of marshes and bog

• Was present before humans

• Natural sources: volcanoes, oceans,

• Relative effects per molecules: 1

Tropospheric ozone

• Produced by the photochemical breakdown of NO2 and subsequent reactions with oxygen

• Wasn’t present before humans

• There aren’t any natural sources

• Relative effects per molecule: 2000

CFCs

• Used in aerosol propellants, fire extinguishers, refrigerators, solvents and in expanded foam plastics

• Wasn’t present before humans

• There are no natural sources

• Relative effects per molecule: 25000

Methane

• Anaerobic respiration by microbes in paid fields, landfill sites and the intestines of livestock. Also produced during the formation of fossil fuels and released by the ventilation of coal mines, leaks from natural gas fields and pipelines

• Was present before humans

• Natural source: anaerobic decomposition

• Relative effects per molecule 25