Greenhouse effect (global warming)
Env sci p6-13
Gaia atlas P110 -13
3.4.1. Describe the role of greehouse gases in maintaining mean (average) global temperature.
- The gases in the atmosphere are natural, for example swamp gas or methane comes from swamps , cows etc as it has done for many years, unfortunatley there is more and more of this gas produced leading to global warming. These gases are what keeps the planet at a farily constant temperature since in space there is a very large diurnal range varying from freezing to extremely warm in such a way as to prevent life.
Greenhouse - glass alows UV in but prevents IR getting out
IR = heat therefore greehouse is hotter
Incoming UV radiation
- passes through the atmosphere
- heats up the Earth surface
heat is given off by earth as IR but it is trapped by gases in the atmosphere e.g. carbon dioxide
if no atmosphere then 32°C lower
now average = 15°C
problem - enhancement of the greenhouse effect.
200 PPM = 0.02
355 PPM = 0.036
How much warmer
Since 1900 - 0.8°C
3.4.2 Describe 4 ways in which humans activities add to greehouse gases, and discuss 4 ways in which global emissions of greenhouse gases can be reduced.
UV - High energy (short wave)
IR - lower energy (long wave)
1) Deforestation/burning of fossil fuels.
- both affect carbon dioxide levels.
- CO2 contributes most to the enhancment of the greenhpouse effect.
- Carbon cycle - sinks/resevoirs - oceans
- vegetation e.g. tree
- Carbonate rocks e.g. limestone/chalk
- fossil fuels (Coal, oil, Natural gas)
Major CO2 releases
1) burning coal, oil, gas
2) deforestation- burn trees- release carbon dioxide
- stops trees absorbing Carbon Dioxide
3) Motor vehicle exhausts - produce carbon dioxide
(petrol/diesel burned - from fossil fuels)
1700's industrial revolution
we add 7 billion tonnes every year to the atmoshpere
2/3 - burning fossil fuels
1/3 - deforestation
CO causes 50% of global warming
Cattle farming,/rice fields
- produced by anaerobic bacteria (respire without using oxygen)
- found in bogs, swamps, marshes, paddy fields, (rice)
- digestive systems of ruminants
- cows, sheep, camels
(bacteria help to digest cellulose)
- large rotting rubbish tips
How much Methane?
Co- 355 PPM
Methane - 1.7 ppm
accounts for fifteen percent of global warming
25 times better than carbon dioxide at absorbing infra red radiation
increasing at a rate of 0-6 to 1 percent a year
Major contributor = India (cows (200 litres/paddy fields)
-burning fossil fuels eg. Fumes from car exhausts
- burning coal, oil in power stations and boilers
- de-nytrifying bacteria can convert nitrate fertilizers to nitrous oxides.
Account for 6% global warming/greenhouse effect.
4) CFC's - chlorofluorocarbons
sources - propellants in aerosol cans.
- coolants in refrigerator
- expanders in plastic insulating from e.g. Burger King boxes
cfc's are 100,000 timesworse than Carbon dioxide as greenhouse gases
account for 22% of global warming.
Montreal protocol - CFC's banned
But very long "residence time"
6) Water vapour - very important greenhouse gas but not affected by man
4 ways of reducing global emissions of greenhouse gases
1 - reduce use of fossil fuels
-implies renewable energy sources should be used.
- geo thermal
- biomass (fuelwood)
alternative - nuclear (environmental problems)
2) Energy efficiency
- use more efficiency machines
e.g. better cars, more fuel efficient
- building insulation
e.g. buildings insulation keep the heat in
- power stations
e.g. increase their energy efficiency of energy transfer
+ use more efficient electricity transmission systems
3) Increase the use of public transportation
e.g. trams, trains, buses.
- uses less energy
- less pollution (use electricity)
- environmental benefits - traffic, noise, road building
use of raw materials e.g. steal
- make it economically, "better sense" (expensive cars, cheap trains, expensive road taxes, expensive fuel)
- use carbon and nitrogen filters in power stations
- remove the plluting gases
5) CFC's use- reduce it (ref. To ozone problem)
6) Collect all the methane that leaks from land fill sites
(use it as fuel? - if you collect the carbon dioxide)
7) stop deoforestation
i burning wood releases carbon dioxide
II trees remove carbon dioxide from air by photosynthesis
8) Ban cars/trucks that have catalytic converters - clean up the car exhaust fumes.
Discuss qualitatively the effects of increased mean global temperature on the planetary distribution of biomes and consequently on global agriculture.
By 2100 it is guessed it will rise from 1.5°C to 4°C, average 2.5°C
Since 1940 it's gone up by 0.6°C
Increase in evaporation which will lead to increase in watour vapour in atmosphere.
Leads to more clouds and rain
Water vapour aborbs infra red radiation implying that the greenhouse effect will be in a cycle or positive feedback.
2) Temperature rise leads to a change in plant and animal distribution
e.g. spread of malarial parasite northwards
3) Increased numbers of storms, cyclones.
Cold area may get colder and hot areas may get hotter.
Where rainfall is already scarce there is no rain therefore the crops fail.
North American grain belt - conditions get drier therefore less productive shift to N of Agriculutral zones so that there is an increased amount of crop growth in the north.
4) Increased sea levels, predictions for increased sea levels vary from 40cm by 2100 while another says by 200 centimeters i.e. 1-2 cm a year
why? - melting of polar ice caps.
- thermal expansion of water - hot water takes up more space
problems? - drowned cities,
- drowned estuaries, deltas, agricultural land
- salt contaminated natural water
5) Extinctions - pace of change of temp. rise is very rapid therefore species can't keep up.
Shrinking tundra implying a drecreasing habitat for penguins, walruses, polar bears and other such creatures.
6) temperature rise: increased photosynthesis co2 goes down and greenhouse effect slows down and retreats.
7) Melting ice caps - release of methane trapped in ice
= greenhouse effect rise
= positive feedback
8) Increased rate of decomposition = bacteria + funghi work faster.
= increased methane + CO2 release (positive feedback)
9) tree line will move northwards 100-150 km by every one degree rise
Scandinavia, Russia, Canada, - boreal forest will replace the tundra biome.
Southern extent of the treeline may move north due to competition with grasses.
10) Possibly the gulf stream may stop
Prevention of global warming
1) Incoming radiation may fall due to volcainic eruptions, clouds and forest fires.
2) return of the ice age ~every 20,000 years
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