1. GREENHOUSE EFFECT
Eylül Baylaz
12-C

2. The Greenhouse Effect is basically, the trapping of heat in the atmosphere.
It was discovered by Joseph Fourier in and first investigated quantitatively by Svante Arrhenius in 1896.
In the absence of the greenhouse effect the Earth's average surface temperature would be about -19 °C, but now it is about 16 °C, which is the optimum temperature for organisms to live.
Greenhouse Effect

3. Greenhouse Effect Process
The electromagnetic radiation from the Sun, is reflected as infrared radiation from the Earth’s surface.
Some of this infrared radiation is absorbed by the greenhouse gases in the atmosphere.
The absorbed energy in the atmosphere reradiates and warms up the surface of Earth.
Greenhouse Effect Process

7. Greenhouse Effect Process
In other words, the greenhouse effect allows visible and UV light of short wavelength to pass through the atmosphere, to heat the air and the Earth, but it traps the longer wavelength infrared heat rays, emitted from the warm soil and air, therefore raising the temperature of the atmosphere.
The rate of this process is increasing as more than neccessary greenhouse gases are being produced.
Greenhouse Effect Process

8. The reason why the rate of greenhouse effect process increases, is that the gases that absorbs the radiated energy from the Earth’s surface increases.
The major greenhouse gases are:
Methane CH4
Water Vapour H2O
Carbondioxide CO2
Dinitrogen Monoxide N2O
Ozone O3
Chlorflourocarbons CFCs
Greenhouese Gases

9. Atmospheric concentrations of the greenhouse gases have increased significantly since the industrial revolution: CO2 increased 25%, CH4 increased over 145% and N2O around 15%.
The usage of CFCs are in decline as the usage is being controlled by legislation.
However not all the gases have the same ability to trap infrared radiation. Their atmospheric concentrations and atmospheric lifetimes differ from one another.
Greenhouse Gases

10. Greenhouse Gases, Sources and Effectiveness

12. Global Warming
Global warming is the increase in the average temperature of the Earth's near-surface air and oceans. It is caused by the increase in the greenhouse effect.
Mean surface temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980
Global mean surface temperature anomaly relative to 1961–1990

13. Global Warming
The rate of change in the temperature is increasing significantly nowadays than any other changes observed in the last 10,000 years.
Ice cores provide evidence to the increase the in the concentration of greenhouse gases over the past 800,000 years. Both CO2 and CH4 vary between glacial and interglacial phases, and concentrations of these gases correlate strongly with temperature, i.e. Directly proportional.

14. Effects of Global Warming
The effects of Global Warming over the last century have resulted in:
An increase in temperature by about half a degree centigrade,
About cm worldwide rise in sea levels resulting from the partial melting of glaciers and polar ice-caps and the physical expansion of ocean water caused by warmer temperatures.

15. What Can Be Done To Prevent Global Warming From Progressing?
We should avoid the excess usage of air conditioners, deodorants, etc.
We should lead people to use public transport.
We should limit the usage of fossil fuels.
We should prevent forest fires.
We should increase afforestation.

16. Questions Appeared in the IB Exams
The natural greenhouse effect can be summarised in these steps.
I. About half of the radiation entering the Earth’s atmosphere is absorbed by the Earth’s surface.
II. This absorbed radiation is re- radiated from the Earth’s surface.
III. Greenhouse gases in the atmosphere absorb the radiation from the Earth’s surface and re-radiate it back to the Earth’s surface.
One predicted consequence of the enhanced greenhouse effect is rising sea levels. Outline two different ways in which this could happen.
(Total 2 marks)
Global warming is thought to be partly caused by the increasing concentration of carbon dioxide in the atmosphere. Discuss the effects of global warming.
(Total 3 marks)
Large-scale combustion of fossil fuels has been a major source of increased levels of CO2 in the atmosphere.
(a) Describe a possible effect of higher levels of CO2 in the atmosphere.
(1)
(b) Explain how the effect in (a) is caused by the interaction between CO2 and different types of radiation in the atmosphere.
(2)

17. (a) List two gases which contribute to the greenhouse effect.
(1)
(b) Explain how greenhouse gases cause global warming.
(c) State one man-made source of particulates and outline the effect of particulates on the Earth’s surface temperature.
(2)
(Total 6 marks)

18. The natural greenhouse effect can be summarised in these steps.
I. About half of the radiation entering the Earth’s atmosphere is absorbed by the Earth’s surface.
II. This absorbed radiation is re-radiated from the Earth’s surface.
III. Greenhouse gases in the atmosphere absorb the radiation from the Earth’s surface and re-radiate it back to the Earth’s surface.
(a) (i) Identify the part of the spectrum from which most of the absorbed radiation in step I comes.
(1)
(ii) Identify the part of the spectrum from which most of the radiation in step II comes.
(iii) Explain on a molecular level, how greenhouse gases absorb the radiation in step III.
(iv) The term enhanced greenhouse effect is sometimes used to describe the increasing effect of human activity on the natural effect.
Explain why, with reference to one of the steps above, the greenhouse effect may be increasing.
(2)
(b) “Carbon dioxide is the most significant greenhouse gas.”
“Methane is a more important greenhouse gas than carbon dioxide.”
Explain how both these statements can be considered correct.
(Total 7 marks)

19. The term greenhouse effect is used to describe a natural process for keeping the average temperature of the Earth’s surface nearly constant.
(a) Describe the greenhouse effect in terms of radiations of different wavelengths.
(4)
(b) Water vapour acts as a greenhouse gas. State the main natural and man-made sources of water vapour in the atmosphere.
(2)
Natural source
Man-made source
(c) Two students disagreed about whether carbon dioxide or methane was more important as a greenhouse gas.
(i) State one reason why carbon dioxide could be considered more important than methane as a greenhouse gas.
(1)
(ii) State one reason why methane could be considered more important than carbon dioxide as a greenhouse gas.
(d) Discuss the effects of global warming on the Earth.
(Total 12 marks)