The major anthropogenic sources of greenhouse gases
- Carbon dioxide
- Methane
- Oxides of nitrogen
- Chlorofluorocarbons (CFCs)
- Tropospheric ozone
Carbon dioxide - human activity
Combustion of fossil fuels, deforestation (Deforestation –>tropical rainforests => stops photosynthesis occurring, so that less atmospheric carbon dioxide is fixed into organic material, + likely to be more organic material being burned or decomposed –> + CO2 is being released into the air
Methane - human activity
Anaerobic bacteria in paddy fields, landfill sites and the intestines of livestock. Methane is produced during the formation of fossil fuels and released by the ventilation of coal mines, leaks from natural gas field and pipelines
Oxides of nitrogen - human activity
Oxygen and nitrogen from the air react at high temperatures a in vehicle engines and power stations. They are then released into the atmosphere in the exhaust gases
Chlorofluorocarbons (CFCs) -human activity
CFCs were used as aerosol propellants, fire extinguishers, refrigerants, solvents and in expanded foam plastics
Tropospheric ozone - human activity
Produced by the photochemical breakdown of NO2 and subsequent reaction with oxygen
Carbon dioxide - approximate relative effect per molecule
1
Methane - approximate relative effect per molecule
25
Oxides of nitrogen - approximate relative effect per molecule
2000
CFCs - approximate relative effect per molecule
5600
Tropospheric ozone - approximate relative effect per molecule
25000
Consequences of global climate change
- sea level rise (thermal expansion + melting land ice)
- changes in climate ( wind patterns + precipitation)
- Ocean current changes (el niño + La niña (+ the North Atlantic Conveyor))
- Ecological changes (temperatures + etc)
Explain what temperature rise may cause to plants
Temperature rise may cause plants to grow faster. This could provide more food for herbivores such as butterflies and moth caterpillars. But many plants produce toxins that build up in their leaves to protect them from being eaten. If plants growth begin earlier in the year, the toxins may build up sooner, which could kill the caterpillars.
Explain what could happen to plants in drier period
Plants with shallow roots may cope less well with drier periods than those with deeper roots.
Explain how ecological changes , such as changes in temperatures, could affect hibernating animals
Species that hibernate may benefit by being able to feed for more of the year, or suffer by being disturbed more frequently when they should be asleep
Precipitation changes may cause wetland habitats to…
Enlargement or shrink
What may happen to dormouse hibernation?
Dormouse hibernation may be disturbed by warmer winters, causing them use up stored fat. They may starve before spring arrives, when they could start feeding again.
What could happen to oak trees in drier period?
Oak trees have deep roots and will be able to survive droughts better than shallow- rooted beech trees,whose actually dry leaves may die during dry weather.
Explain how geese migration may changes
Geese that breed in Arctic areas during the summer may not need to migrate so far south if winters become warmer
What could happen to coastal salt marsh habitats if sea levels rise?
A rise in sea level would flood the coastal salt- marsh habitats needed by many wading birds, such as dunlin
The distribution of species may change as conditions change and they colonise areas that have become suitable. For some species this may not be possible for the following reasons
- they may colonise new areas more slowly than they disappear from their old range, this is very likely for species that grow slowly, such as trees
- suitable areas may not be available
- human land use may block movement
- species live in interdependent communities of species. All the species will not be able to move at the same speed
Say a few reasons why it is difficult to predict climate change
- difficult to tell whether an event is caused by human actions or not
- difficult to identify trends are there may be limited historical data (some cannot be trusted)
- many natural effect are interconnected so one change may have unexpected effects
- somme changes are very slow
- may occur at different locations at different times
- we do not fully understand how all the Earth’s climate systems work
Say 5 positive feedback mechanism about raised temperatures
- increase the rate of composition
- reduce size the area of ice and snow –> less sunlight is reflected
- methane can eventually be released from methane hydrate in marine sediments
- melting permafrost releases methane gas bubbles that were trapped in ice
- forest + areas with peat soils to become drier -> fires more often and loger
2 negative feedback mechanism for raised temperatures
- increased rate of photosynthesis –> store more carbon in biomass
- increase evaporation –> formations of low level clouds –> increase albedo
