Human environment systems
Marjorie Henry, Contributor

I have been discussing the questions given under Section D of the June 2008 question paper, the human-environment systems, for several weeks. In today's lesson, I will begin a discussion on Question 10, the last in this section. The entire question is not given here. However, I would like to state that it is testing the following objectives, as outlined in the syllabus:

• Describe the long-term changes in global temperatures.
• Explain the causes and consequences of global warming, coral reef destruction and deforestation.
• Explain measures used to reduce the emission of greenhouse gases, coral reef degradation and deforestation.

Here is part (a) of Question 10.

(i) Determine the difference in average annual temperature from the 1900 average in

a) 2000

b) 1910

(2 marks)

(ii) During which quarter (1900-1925, 1925-1950, 1950-1975 or 1975-2000) was the change in average annual temperature

a) fastest?

b) smallest?

(2 marks)

Figure 3. Difference in average annual temperature, 1900 - 2000

You have been given a temperature graph as stimulus material. Please note that the unit of measurement is Celsius (written to the left of the graph). I have specifically highlighted this since failure to indicate the unit of measurement in your answer will cause you to lose marks. As you calculate the answer, try to do so as accurately as possible. Use your ruler to help you find the answer. If you did just that, you would have noticed that the squares are 1cm. This makes the job of determining the average annual temperature quite easy.

Here are the expected answers:

(i) (a) The difference in average annual temperature from the 1900 average in 2000 is 0.65¡C. (Note that any answer between 0.65¡C to 0.7¡C would be acceptable).

(b) The difference in average annual temperature from the 1900 average in 1910 is 0.12¡C. (Again, please note that any answer between 0.12¡C and 0.14¡C would be acceptable)

(ii) (a) The change in average annual temperature was fastest during the quarter of 1975-2000.

(b) The change in average annual temperature was smallest during the quarter of 1950-1975.

I will now go on to part (b) of the question.

(b) Describe the process which produces the greenhouse effect.

(4 marks)

The raising of surface temperatures as a result of counter radiation from the atmosphere is known as the greenhouse effect. Energy in the form of light from the sun can pass freely through the covering glass of a greenhouse. When this light energy strikes the enclosed Earth, it is changed to heat energy, which, because of a difference in wavelength, cannot easily pass back through the glass and so is trapped within the structure. As with the glass of a greenhouse, the atmosphere tends to allow solar short-wave radiation in, but partly stops terrestrial long-wave radiation from being lost again to space. Gases in the atmosphere, particularly water vapour and carbon dioxide, act in the same way as the greenhouse glass, letting light pass but obstructing heat.

(Sources: The Atmospheric System by Greg O'Hare et al; Geographic Fundamentals by W. G. Stone et al)

The discussion will continue in the next lesson.

Past student of Montego Bay High School, Pauline Chambers (left), is presented with a gift of orchids by Karee Parkinson for her constant support to the school at the school's annual prize- giving ceremony, last year in the school's auditorium.