What do you know about the greenhouse effect?
This task can be completed with pencil and paper or online.
This task could be completed by individuals or as a small group discussion. Some items do not have a clear-cut right or wrong answer. This lends the activity to discussions that highlight the ongoing nature of science inquiries, the constructed nature of scientific scales and measures, and the uncertainties created when complex systems (weather, atmosphere) are changing. It also reinforces the "managing self" feature of the activity – that acknowledging when you do not know something is an important part of learning. Different parts of the task could be used in different lessons, as a quick self-review exercise.
| Y10 (08/2006) | ||||
| a) | They absorb reflected heat that would otherwise head back out into space (D) | moderate | ||
| b) |
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Atmospheric processes are very complex and several answers could be considered "correct", depending on how the question is interpreted:
The response rates suggest that students are most aware of the third of these ways of determining impact. However 39 percent of students either did not attempt an answer or gave an answer that was not the name of a gas from the table. |
very difficult very difficult difficult |
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| c) |
5. 6. 8. |
Effects about which there is broad consensus agreement in the science community (% who said yes): Sea levels will rise around our coast Violent storms will happen more often Our glaciers will shrink |
moderate moderate easy |
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3. 4. |
Effects mistakenly attributed to global warming: More people will get skin cancer (5% said no, 77% said yes) The air will get dirtier (20% said no, 46% said yes) |
very difficult moderate |
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1. 2. 7. |
Effects where likely regional differences mean one correct answer is not possible: New Zealand will be sunnier overall (45% yes, 30% no) New Zealand will have less rain overall (32% yes, 39% no) Winters will get colder in New Zealand (20% yes, 45% no) |
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Based on a representative sample of 244 Year 10 students in August 2006.
Question a): Interpreting the diagram
30 percent of students incorrectly chose option B. This could provide an opportunity to discuss the need to read the whole question against the possible answers. While the sun does provide the energy that keeps earth warm, it would do so regardless of greenhouse gases (albeit with much more drastic changes of temperature between day and night). Thus their main role is holding in at least some of the heat that would arrive, whether they were there or not, as long as the sun keeps shining. Some students may have chosen this option because they confused the greenhouse effect with the "hole" in the ozone layer. This is known to be a common misconception amongst school students.
Question b): Relative effect of greenhouse gases
Atmospheric systems are complex. There is no simple answer to the question of which greenhouse gas has the greatest effect. This question was more difficult than we intended it to be! However we have left it as part of this mini item-bank because of the systems-thinking discussions it could generate. Also, some people use the role of water vapour to argue that humans have not caused the greenhouse effect to increase at all (see for example http://www.geocraft.com/WVFossils/greenhouse_data.html).
In the event most students seem unaware that water vapour:
- is a greenhouse gas; and
- plays a large role in the global warming that keeps earth at a habitable temperature
Go to Further Resources for a list of websites that help unpack this complexity.
Question c): Impacts of global warming
Those students who appeared to answer part b) randomly seemed more likely to engage with this part as intended. This might be because the items more obviously link global warming to everyday issues and concerns. The overall pattern of responses is shown in the next table.
| Possible enhanced greenhouse effect |
Yes % |
No % |
Don't know % |
Missing/unclear % |
|
| 1. | New Zealand will be sunnier overall | 45 | 30 | 21 | 3 |
| 2. | New Zealand will have less rain overall | 32 | 39 | 27 | 3 |
| 3. | More people will get skin cancer | 77 | 5 | 15 | 3 |
| 4. | The air will get dirtier | 46 | 20 | 31 | 3 |
| 5. | Sea levels will rise around our coast | 57 | 21 | 20 | 3 |
| 6. | Violent storms will happen more often | 40 | 25 | 33 | 3 |
| 7. | Winters will get colder in New Zealand | 20 | 45 | 31 | 3 |
| 8. | Our glaciers will shrink | 72 | 5 | 21 | 3 |
It is interesting that 77 percent of students agreed that global warming could lead to increases in skin cancer. This appears to be related to a conflation of this issue with the ozone layer issue (see Illustrating the enhanced greenhouse effect). Similarly 46 percent agreed that the air will get dirtier, seemingly conflating global warming issues with air pollution in general. However more students were unsure about this item. Note that these misunderstandings could be predicted from the international science education research literature, so New Zealand students are not alone in thinking these things.
Many students also seem to think that warming will be pleasant for us, causing sunnier conditions (45 percent agreed). Congruent with this, 46 percent disagreed that winters could get colder and 25 percent disagreed that there could be an increase in violent storms. Two of these items were selected as "don't know" responses by nearly a third of the students. This could be read in one of two ways, because there is not necessarily one correct answer to weather-related effects, which will differ regionally. You might want to use this item "as is", to discuss this point about the limitations of very general questions, or you might want to alter the wording to say "our area will be…." if you want to find out whether students are aware of local effects.
Results of this trial suggest many students need to begin at the very beginning and find out about greenhouse gases – What are they? Where do they come from? Can we see them in the air? Why are they increasing? In what ways are they like/not like other types of "air pollution"? Go to Further resources for some helpful websites.
Later students could research and imaginatively represent the "life" of one specific greenhouse gas particle, to get a feel for the atmosphere as a system (in much the same way as younger students might be encouraged to think about "my life as a water particle").
You may want to clearly delineate between global warming, and to other commonly discussed atmospheric issues such as the ozone layer thinning. As part of this discussion you could clearly locate the increased risk of skin cancer as an ozone thinning problem rather than a global warming issue.
The idea that warmer temperatures equal nicer weather clearly needs to be critiqued. The impact of warm air masses on weather systems could be explored. Regional differences in effects (both locally and globally) could be investigated.
This task could be a springboard for developing the "nature of science" point that scales are human constructions. They often have an arbitrarily (but not irrationally) decided base point – in this case carbon dioxide is given a measure of 1 against which every other greenhouse gas's GWP is compared. A further important understanding for democratic decision-making is that different scales can be used to measure the same phenomenon in different ways.
Useful websites:
- http://en.wikipedia.org/wiki/Greenhouse_gas
- http://www.enviroliteracy.org/article.php/428.html
- http://www.geocraft.com/WVFossils/greenhouse_data.html ( for an example of the argument that humans have not caused the greenhouse effect to increase)