1.7 Maintaining our atmosphere
Unit 1, theme 1, My Wider World
quiz
• http://www.bbc.co.uk/schools/gcsebitesize/sc
ience/ocr_gateway_pre_2011/rocks_metals/6
_clean_air/quiz/q91424878/
Learning objectives
• What is the natural greenhouse effect?
• How do greenhouse gases help keep
temperatures stable and warm enough to
support life?
Earth’s atmosphere
• Made up mostly of
nitrogen (N2) and
oxygen (O2)
• Tiny amount of
carbon dioxide (CO2)
and water vapour
(H2O)
• Very tiny amount of
Argon – this is inactive
Nitrogen N2
• This gas makes up most
of the atmosphere
• Doesn’t easily react
with other chemicals
• Sometimes reacts with
oxygen to form nitrates
that are absorbed by
plants and used in
making proteins
Water vapour H2O
• Amount of water vapour varies a lot
depending on where you are.
• Usually between 1% and 4%
Carbon Dioxide CO2
• The tiny amount of carbon dioxide in the
atmosphere is enough for the all the plants in
the world to make the food they need to live.
• Photosynthesis
• Plants convert CO2 and water to glucose and
O2
Oxygen O2
• The gas living organisms use in respiration
• Not much life could exist without it
• When we burn something they react with
oxygen to form oxides
question
• Which gases in our atmosphere are used by
living organisms?
Greenhouse gases
•
•
•
•
•
Have a bad reputation
The greenhouse gas effect is often in the news
Global warming
Climate change
But without greenhouse gases there would be
very little life on earth
Video links
• http://www.telegraph.co.uk/earth/environment/
globalwarming/
• http://www.bbc.co.uk/learningzone/clips/globalwarming-threat-to-ski-industry/6007.html
• http://www.bbc.co.uk/learningzone/clips/eviden
ce-for-global-warming-sea-levelchange/1497.html
• http://www.bbc.co.uk/learningzone/clips/eviden
ce-for-global-warming-polar-ice-caps/2553.html
The sun
• Life could not exist on earth without the sun
• It provides the energy for photosynthesis
• It provides the energy which prevents the
planet from freezing
Heating of earth
• Energy is radiated by the sun as shortwave
radiation
• Mainly light energy
• Warms the surface of the earth
Greenhouse gases – carbon dioxide
and methane
• Earth radiates long radiation back into space
• Greenhouse gases let shortwave radiation
through but absorb longwave (infrared)
radiation
• This traps energy in the atmosphere, keeping
the planet warm
question
• How do greenhouse gases raise the earth’s
temperature?
• http://www.youtube.com/watch?v=Hi3ERes0
h84
• Without greenhouse gases earth would be 33o
colder
• Most of the planet would be encased in ice
Humans
• Are increasing the amount of greenhouse
gases in the atmosphere
• This is making the planet warmer
• Scientists argue this might make our climate
more extreme
• http://www.enwin.com/kids/conservation/gre
enhouse_effect.cfm
questions
• Why are greenhouse gases useful to have in
the atmosphere?
• What problems are caused by too much
greenhouse gas?
Carbon Dioxide
• The main
greenhouse gas
• Gets into the
atmosphere by
• Respiration of
living things
• Burning of fossil
fuels
Methane
• Another greenhouse gas
• Waste product of cattle and other livestock
• Its warming effect is 23 times greater the
carbon dioxide
• However there is a lot less of it
Water vapour
• Also acts as a greenhouse gas
Key points
• The earth’s atmosphere contains mostly nitrogen
and oxygen, with small amounts of carbon
dioxide, water vapour and argon
• Shortwave radiation (light) from the sun passes
through the atmosphere to warm the Earth
• Longwave radiation, emitted by the Earth, can be
absorbed by greenhouse gases. This natural
greenhouse gas effect keeps the Earth warm
enough to inhabit.
Useful websites
• http://www.bbc.co.uk/schools/gcsebitesize/sc
ience/ocr_gateway_pre_2011/rocks_metals/6
_clean_air1.shtml