6.2 The greenhouse effect and global warming

Question 1

EXAM QUESTION

Clearing the forests and burning the vegetation affects the carbon dioxide concentration in the atmosphere.
Describe how and explain why (4)

Answer 1

1. Carbon dioxide concentration increases;
   Clearing
2. No/Less vegetation so no/less photosynthesis /
   photosynthetic organisms;
3. No/Less carbon dioxide removed (from the atmosphere);
   Burning
4. Burning/combustion releases / produces carbon dioxide;

Question 2

EXAM QUESTION

Climate change has resulted in an increase in the concentration of salt (salinity) in soil water in some parts of the world. Crop plants do not grow when soil salinity is 2% or higher.

Suggest how climate change could cause an increase in soil salinity (2)

Explain why crop plants do not grow when soil salinity is 2% or higher. (2)

Answer 2

1. Increase in temperature / (global)
   warming;
2. Evaporation (of water from the soil) /
   flooding by sea water / less rainfall;

1. Soil has reduced/low(er) water
potential / crop/plant/roots have
higher water potential;
2. Osmosis from plant / diffusion of
water from plant;

Question 3

Greenhouse gases:

Define greenhouse gases

Carbon dioxide (3)

Methane (2)

Answer 3

Gases that cause more heat energy to be trapped in the atmosphere, raising the temperature of the Earth’s surface (e.g. carbon, methane)

Main greenhouse gas
Remains in atmosphere for very long time
Increasing due to human activities

Produced in:
Decomposition by microorganisms
Digestion by microorganisms

Question 4

The greenhouse effect:

Describe it
Caused by solar radiation…(4)

Answer 4

Continuous process that maintains warm temperature of Earth (17 degrees)

Some reflected back to space
Some absorbed by atmosphere
Some reaches Earth’s surface
-Radiated back by clouds and greenhouse gases

Question 5

Global warming:

Global temperature is… due to…and…
Support (2)
Against (1)

Answer 5

Global temperature is increasing due to human activities and increased CO2 concentration

CO2 concentration increased since industrial revolution
CO2 = greenhouse gas

Always been fluctuations in temperature

Question 6

Consequences of global warming:

Effects? (4)

Negatives? (3)

Positives? (3)

Answer 6

Increased temperature
Increased rainfall
Increased frequency of extreme events - storms, flood, drought
Altered seasons

Polar ice caps melting - extinction
Rise in sea level - floods cause increased land salinity (hard to cultivate)
Altered niches - migration/distribution (e.g. only xerophytes)

Fill reservoirs
Allow crops to be grown in areas presently too cold
Increased rate of photosynthesis - double harvest