IB Diploma Environmental Systems and Societies

1. Topic 6
Atmospheric Systems and Societies
6.1 Introduction to the Atmosphere

2. Composition of Air
nitrogen; 78.1%
oxygen; 20.9%
carbon dioxide;
0.038%
argon; 0.93%
other gases, 0%

3. Structure of the Atmosphere
• It is a mixture of solids, liquids
and gases held in place by the
Earth’s gravity
• Close to the surface (first 10 km
the troposphere), the
composition is fairly constant. It
changes at higher altitudes
• Certain gases are characteristic
of different altitudes
• A layer of ozone occurs at an
altitude of 10 – 50 km (this is
called the stratosphere)
Altitude
(km)
Most
Significant
Gas
10 - 50 ozone
100 - 200 nitrogen
200 - 1100 oxygen
1100 - 3500 helium
> 3500 hydrogen

4. Structure of the Atmosphere
Pressure(mb)
OZONE
LAYER
Mount Everest

5. The Atmospheric System
• It has inputs and outputs (of energy and
matter), processes and feedback mechanisms
– It can therefore be referred to as an OPEN SYSTEM
• It is also dynamic (changing)
– Atmospheric conditions have changed over time
and change with location around the planet and
altitude

6. The Atmospheric System

7. The Troposphere
• The atmosphere is split into 5 layers
– The troposphere (from tropein – to change/mix)
– The stratosphere (from stratus – spread out)
– The mesosphere (from meso –middle)
– The thermosphere (from thermo – heat)
– The exosphere (which makes up the boundary with space)
• Although the biosphere encompasses the whole atmosphere, most living
systems are restricted to the troposphere (up to about 10km above sea
level)
• Since we live on the lithosphere, most human effects on the atmosphere
largely affect the troposphere and extend up to the stratosphere (about 10 -
50km above sea level)

8. The Troposphere
• The troposphere contains about 75% of the entire
mass of the atmosphere, 99% of its water vapour and
most of the dust
• For these reasons most clouds form in the troposphere
• These play an important role in creating the Earth’s
albedo
• It is where weather occurs

9. The Troposphere
• Many gaseous pollutants are disposed of into
the atmosphere and much of them stay in the
troposphere where they are particularly
damaging to human health (e.g. tropospheric
ozone which causes smog)
• Waste CO2 spreads throughout the entire
atmosphere and contributes to global
warming

10. Global Warming

11. Questions
1. Describe the composition of the atmosphere
2. Produce a systems diagram of the
atmosphere
3. Explain why the troposphere is of particular
interest in the study of Environmental
Systems and Societies