Greenhouse Effect (Lecture 14)

Basic Climatology
BCE 22012
Greenhouse Effect
1
At the end of this session you will be able to;
1. Describe reasons for unbalanced energy budget.
2. Explain the greenhouse effect.
3. Define greenhouse gases.
4. Deliberate sources of emission of greenhouse gases.
5. Discuss the current measures to minimize the affect of

human activities on greenhouse effect.
2
Energy cycle
• Moves back and forth between spheres.
• Plants use solar energy to make food.
• Animals eat plants for energy.
• Solar energy.
• Drives winds and weather.

Earth’s Energy
• Most comes from the sun.
• A tiny fraction from
✓ Ocean tides
✓ Geothermal
✓ Lava or magma
• Not created or destroyed.
• Transferred between spheres.

Energy Budget
5
Energy budget
• A way to keep track of energy transfers into and
out of earth’s system.
Unbalanced energy budget

• Can increase or decrease earth’s temperatures.
• Increasing greenhouse gases in the atmosphere

global warming can occur due to changes in
energy budget.
Greenhouse Effect
Step 1: Solar radiation reaches the Earth's atmosphere some of
this is reflected back into space.
Step 2: The rest of the sun's energy is absorbed by the land
and the oceans, heating the Earth.
Step 3: Heat radiates from Earth towards space.
Step 4: Some of this heat is trapped by greenhouse gases in
the atmosphere, keeping the Earth warm enough to
sustain life.
• Step 5: Human activities such as burning fossil fuels,
agriculture and land clearing are increasing the amount of
greenhouse gases released into the atmosphere.
Step 6: This is trapping extra heat, and causing the Earth's
temperature to rise.
Greenhouse Effect
• is the term that refers to a natural process work out by the
earth’s atmosphere.
• If the Earth had no atmosphere, its average surface

temperature would be very low of about -18℃
rather than the comfortable 15℃ found today.
• is due to a group of gases called greenhouse gases which

affect the overall energy balance of the earth's system by
controlling the energy radiation.
Greenhouse Effect
• Since the incoming light is at different frequencies than the
outgoing light, some outgoing light can be Preferentially
absorbed by various “Green House Gases”.
Natural Greenhouse Effect
• Due to green house gases, the atmosphere absorbs
more infrared energy than it re-radiates to space,
resulting net warming of the earth
atmosphere system and of surface temperature.
Enhanced Greenhouse Effect

• With more greenhouse gases released to the
atmosphere due to human activity more infrared
radiation will be trapped in the Earth’s surface which
contributes to increase natural green house effect.
Greenhouse gases
• Comprise less than 1% of the atmosphere.
• Their levels are determined by a balance between

“sources” and “sinks”.
• Sources and sinks are processes that generate and

destroy greenhouse gases respectively.
• Human affect greenhouse gas levels by introducing

new sources or by interfering with natural sinks.
Greenhouse gases
• Are relatively transparent to incoming solar radiation
but they absorb outgoing infrared radiation emitted
from Earth's surface.
• The most abundant greenhouse gases in the

atmosphere are;
Water vapor (H2O)
Carbon dioxide (CO2)
Methane (CH4)
Nitrous oxide (N2O)
Ozone (O3)
Chlorofluorocarbons (CFCs)
Hydrofluorocarbons (HFCs)
Contribution to Greenhouse Effect
Non-gas contributors
• Clouds, also absorb and emit infrared radiation and
thus have an effect on greenhouse gas radiative
properties.
• The major non-gas contributor to Earth's greenhouse

effect.
Sources of emission of greenhouse gases
• Burning of fossil fuels and deforestation leading to higher CO2
concentrations in the air.
• Livestock enteric fermentation and manure management, paddy
rice farming, land use and wetland changes leading to higher
methane atmospheric concentrations.
• Use of chlorofluorocarbons (CFCs) in refrigeration systems, and
use of CFCs and halons in fire suppression systems and
manufacturing processes.
• Agricultural activities, including the use of fertilizers, that lead to
higher nitrous oxide (N2O) concentrations.

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Basic Climatology

1. Describe reasons for unbalanced energy budget.

2. Explain the greenhouse effect.

3. Define greenhouse gases.

4. Deliberate sources of emission of greenhouse gases.

5. Discuss the current measures to minimize the affect of

• Plants use solar energy to make food.

• Animals eat plants for energy.

• Drives winds and weather.

• A tiny fraction from

• Not created or destroyed.

• Transferred between spheres.

Unbalanced energy budget

• Increasing greenhouse gases in the atmosphere

• If the Earth had no atmosphere, its average surface

• is due to a group of gases called greenhouse gases which

Enhanced Greenhouse Effect

• Their levels are determined by a balance between

• Sources and sinks are processes that generate and

• Human affect greenhouse gas levels by introducing

• The most abundant greenhouse gases in the

• The major non-gas contributor to Earth's greenhouse

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