6 – the issue of global warming

Greenhouse gases
Maintain the average temperature by trapping a fraction of the outgoing heat radiationWater vapour, carbon dioxide, ozone, methane, nitrous oxide
Factors affecting CO2 concentration
Anthropogenic factors:Industrialization, burning fossil fuelsDeforestationoil and petrolNon-anthropogenic factors:Volcanic activity
Environmental effects of global warming
Retreat of polar icecapsIncrease in sea level and coastal floodingChange in biome and species distribution
The role of greenhouse gases in maintaining mean global temperature
Only 55% of solar energy is reaches the surface of the earth. 45% is absorbed or reflected by the gases in the atmosphere.Out of the 55%, 4% is reflected back to space.

51% is used for photosynthesis, heat, and evaporation.

What are the main greenhouse gases? How do human activities add to them?
Carbon dioxide (54.7%) – biggest contributor is the burning of fossil fuelsMethane (30%) – increasing by 1% per year due to human activities, cattle. Many developed countries capture methane and use it as a source of energyNitrous oxide (4.9%)Water vapour – largest effect in trapping heat energyChlorofluorocarbons – very high global warming potential GWP
chlorofluorocarbons (CFC)
chemicals made by humans which destroy the ozone layer when they reach the stratosphere, but acts as greenhouse gases in the troposphere.

Atmospheric layers
thermospheremesospherestratosphere (ozone layer)troposphere
Potential effects of increased mean global temperature
Rising sea levels – ice melting and water expanding – potential flooding – warm water absorbs less CO2, which misbalances the pHThe melting of glaciers could open up new trade routesMethane clathrate – a form of ice under the Artic ocean floor that traps methane. If it were to melt and reach the surface, the release of methane might trigger a rapid increase in temperatures. Methane can also be stored in tundra’s permafrost.A small increase in temperature can kill plankton, the basis of many marine food webs.

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Could decrease biodiversity in plants – unlike animals, plants may take too long to move to a cooler area. Possible extinction of polar species.Spread of tropical diseases.Reduced heating bills for households.Possibly – increased human migrationDrought may have a negative effect on national economiesIf rivers don’t freeze, hydroelectric power can be generated in higher altitudesAgricultural production may increase in higher altitudes but fall in the tropics

Pollution management strategies
International agreements, national actions, personal lifestyle changes