Pal J. Kirkeby Hansen

Oslo University College, Oslo, Norway

European Meteorological Society, Education Committee

PalKirkeby.Hansen@lu.hio.no

The greenhouse effect and the effects of the ozone layer (GEEO) is one of 6 main topics in the subject Nature, Society and Environment (NSE, 30 ECTS credits) given to all third year teacher students at Oslo University College (OUC). The students are trained for primary and lower secondary education. As future teachers they will teach GEEO in the subject Science and the environment, grade 10 (age 15 years) – last grade in Norwegian compulsory school. GEEO was introduced in teacher education in 1993. Since then the lecturers at OUC has developed a set of teaching strategies which support the students' development of knowledge and teaching skills. With some light adjustments, the same strategies could be used in grade 10. During the academic year 2000/2001 a group of 52 students took a pre test at the start of the year, post test at the end of the GEEO period and written exam at the end of the year. Pre test confirms well-known features from other research: Many students have alternative conceptions ('life world' knowledge) about the two effects, changes in the effects, and consequences of the changes for nature and societies. Many confuse elements of explanation concerning greenhouse effect and ozone layer depletion. Post test and exam shows, however, that most of the students developed adequate knowledge ('scientific' knowledge) and teaching skills. They are well prepared for teaching GEEO at grade 10. Keywords for the strategies are activity based teaching methods in a social constructivist framework.

All nations have to meet the effects of climate change with adequate political actions. To do so, the governments need to have support from a well informed population for decades to come. The school have since Rio 1992, Agenda 21, been one agent in the struggle for sustainable development. In Norway the result is that education for environmental literacy is an overall goal in The curriculum for the 10-year compulsory school [C10] (1999) implemented in 1997. In grade 10 "pupils should have the opportunity to learn about the greenhouse effect and the effects of the ozone layer" (ibid.). Do Norwegian teacher students develop sufficient knowledge and teaching skills to teach that topic?

Boyes, Chambers and Stanisstreet (1995) did a study of 435 trainee primary teachers' ideas about the ozone layer. Most students seem well informed about the nature of the ozone layer and many are aware of health problems coming with increased UV radiation caused by ozone depletion. Many confuse ozone layer depletion with global warming. 49% are sure or think it is right that "Holes in the Ozone layer are made worse by the Greenhouse effect". Many agree in "If the holes in the Ozone Layer get worse the Greenhouse Effect will get worse [89% and] … there will be more flooding in the world [51%]". Year 1 and 4 students are on same level, but the last are less confident.

Boyes et al. point out some reasons for this and other misconceptions: Learning in this area cannot be experimental. Ozone layer is a dynamic structure with normal differences in concentration in different regions. Therefore an overall change is difficult to envisage. Issues concerning the ozone layer and other global environmental problems are often presented in popular media and other informal sources. Children and students may gain ideas, perhaps erroneous from these media. Some textbooks group together discussions of ozone layer depletion and global warming since both are consequences of atmospheric pollution. We at OUC think another reason could be that the holders of this misconception think 'logical': A thinner ozone layer allows more sunbeams to reach the ground, which will cause increased heating. The students lack basic information that that UV radiation is a minor (1-2%) part of energy from the sun, and even before any ozone depletion almost all UVA (320< λ<400nm) passes through the ozone layer.

Students with art-based background (a majority of primary teachers) were less sure of some of the issues surrounding a major environmental problem. Boyes et al. recommend that the major large-scale environmental issues should be addressed during the training of all teachers. The course should aim to consider the complexity of more 'abstract' global problems like global warming and ozone depletion, as well as provide students with hands-on experience of teaching more tangible, local environmental issues.

Dove's (1996) study of 60 student teacher's understanding of the greenhouse effect and ozone layer depletion concludes that before instruction the students reveal familiarity with the term 'greenhouse effect', but little understanding of the concepts involved. 46% of the students disagreed in the statement "if there was no greenhouse effect non of us would be here", 37% agreed, but with few able to provide reasons for their views. Almost all students have clear understanding that the ozone layer protects the Earth from harmful radiation and that it is currently destroyed by chlorine fluorine carbons (CFC) pollution. Dove think that ozone depletion are better understood than greenhouse effect because the ozone depletion is linked to one cause CFCs pollution, and that this cause is accepted as a fact, while uncertainty still surrounds global warming. CFCs are involved in both cases. Greenhouse effect and global warming are more complicated. Like Boyes et al. Dove reports that the most revealing finding is the widespread misconception that greenhouse effect was result of holes in ozone layer (68%), and this had set up a false chain of reasoning. Dove recommends:

Student teachers must train to explain concepts a novel way. They have to be familiar with and do some own research into children's misconceptions. Student teachers must be aware that knowledge about the greenhouse effect is constantly revised.

Boyes et al. and Dove's research methodology and conclusions seems to be based on a personal constructivist learning theory. Fisher (1998a, b, 2001) have conducted research in the same area on pupils aged 11 to 17+. Fisher's expressed basis is Solomon's (1993) theory of social construction of children's scientific knowledge. This accords with our ideas about learning in science at OUC. We think that concepts and ideas, especially in media focused issues like GEEO, are developed in social settings in or out of school. That is why Fisher's methodology is used in this study. The first research hypothesis is based on Boyes et al. and Dove's findings and our impressions from many years teaching GEEO:

1. Before starting the NSE studies, teacher students are on the same knowledge level in GEEO as pupils in lower secondary school.

The GEEO subject have at OUC for years been planned and taught as if this hypothesis was true. Now it will be tested! If the hypothesis is falsified, we have to adjust practice. We like to start from what the students already know. Regardless of falsification, we like students to be active in their learning process in the college. Our common experience with GEEO teaching is that activities are good starting points for dialogues and discussions which we believe generate good learning. That is background for the second hypothesis:

2. The activity based teaching programme helps the students to develop knowledge and teaching skills in GEEO sufficient for teaching that topic in compulsory school.

Many activities will be described later. The activities will be supported by ordinary lectures, the students work with the literature and with a web site for the subject.

At start of the academic year 2000/2001 the population of third year teacher students was 201 at OUC. The main subject at third year is NSE, stipulated to occupy half the time of the students' work. A random sample of 52 students formed the team which is object in this study. They have taken a pre test at the start of the year, a post test at the end of GEEO period and a written exam at the end of the academic year. This quasi-experimental design limits the external validity of this study. Pre test and post test were carried through in connection with ordinary lectures. The lectures in NSE are not obligatory. That is why fare from all 52 students are present on the tests. This fact decreases the validity further. The exam have higher external validity since all students in the sample are present and 45 of them chose (among two options) to answer the exam set of questions where 'global warming' was the red thread. The choice indicates that DEEO is a popular topic.

Fisher's open-form questions (in Norwegian translation) have been used in the pre and post test. Fisher have developed them from Boyes and Stanisstreet's (1992, 1993) pilot. They used an open-form questionnaire with six questions given to 60 students in order to get a variety of pupils' ideas about the greenhouse effect. From the answers they design the closed questionnaire with 36 statements about the greenhouse effect. Fisher reduced the six questions to four, and supplied four about the ozone hole. "Rather like the interview situation, this provides the respondents with more than one chance to give elements of explanation." (Fisher 2001:5.5.1). The questions are:

(Fisher's questions were translated to Norwegian.)

The questions are open to the students interpretation. 'The greenhouse effect' could be both the normal effect and the increased effect. 'The ozone hole' could be interpreted literary as the Antarctic spring ozone hole (more than 50% temporary depletion) or as the general worldwide small ozone depletion.

Like Fisher, the analyses of the students' answers are formed by Solomon's (1993) theory of social construction of children's scientific knowledge. She argues that the process by which children construct notions for explaining the meaning of events in their daily life is more social than personal. That is why she sorts pupils ideas (about energy) in two categories:

Table 1 shows Solomon's characterizations of her two worlds of knowledge and is supplied by Fisher.

Having four questions on each topic, student's interpretation of the concepts will be cross checked. The categories in the analysis represent authentic student answers from the first reading through. Only the most frequent categories (≥10) on pre or post test are put in tables 2-5.

37 students were present at pre test. 65% write that the greenhouse effect causes warming or causes global warming. Only 22% differentiate explicit between increased and normal greenhouse effect and/or write that the greenhouse effect is essential for life on earth. 57% write that the greenhouse effect is caused by gasses like CO₂ and water vapour or gasses from burning fossil fuel. Life-world knowledge elements are also numerous present: 32% think that the greenhouse effect is caused by a greenhouse layer, an unspecified layer or layer made of CO₂ or pollution blocking the heat rays from letting out. 27% think the layer reflects the heat rays back.

Many students mix elements of scientific knowledge and life-world knowledge in their explanations. The most frequent (≥3) combinations are 3-3, 4-3 and 4-4 scientific and life-world elements respectively. This clustering counts all together only 27%. The variation in the sample is great. Only 11% have combinations with 0 life-world elements. 70% have scientific elements combined with 2 or more life-world elements. The average is 3,11 scientific elements and 2,51 life-world elements.

For comparison: Fisher's (2001:5.5) English pupils age 15/16 (n=31) had average 2,3 scientific elements and 3,2 life-world elements. Pupils age 17+ (n=17) had respectively 3,2 and 2,3 which are quite similar to OUC teacher students. (Test for significance is impossible since Fisher does not give the standard deviation). Fisher's pupils have had no formal teaching in the subject since it was removed from National Curriculum in 1995 (ibid.:4.2). Norwegian teacher students have been taught something about GEEO in science and geography at upper secondary school more then five years ago.

Most (84%) students think of the ozone hole as missing ozone or as ozone depletion. No students link the ozone hole to the South Pole or Antarctic. Most (86%) students can tell correct about some problems coming with an ozone hole (depletion). Only 38% specify CFC pollution as cause of the ozone hole. Life-world knowledge elements are also present: All together 37% use knowledge elements showing that they more or less think that hole in ozone layer causes the greenhouse effect and/or global warming. 35% think that CO₂ pollution alone or together with other effects causes the depletion of the ozone layer or causes ozone hole. This confusion is not on the same level as Boyes et al. (89%, 1995) and Dove's (68%, 1996) teacher students before instruction. That could be due to more general information and awareness about global warming in media the last years in Norway and different experiences in upper secondary school in Norway and England.

Many students mix elements of scientific knowledge and life-world knowledge in their explanations. The most frequent (≥4) combinations are 3-1, 3-2, 3-3, 4-1, 4-2 scientific and life-world elements respectively. This clustering counts all together 62%. The variation is less than in greenhouse effect. Only 16% have combinations with 0 life-world elements. 54% have scientific elements combined with 2 or more life-world elements. The average is 3,24 scientific and 1,59 life-world elements.

Fisher's pupils age 15/16 (n=24) had average 2,3 scientific elements and 2,0 life-world elements. Pupils age 17+ (n=16) had respectively 3,8 and 1,2 which, like the greenhouse effect, are quite similar to OUC teacher students' pre test.

Most students mix elements of scientific knowledge and life-world knowledge in their explanations both about greenhouse effect and the effect of the ozone layer. Many confuse the two effects. Interpreted in a the theory of social construction of scientific knowledge (Solomon 1993) this findings show that the students have tried to use perhaps rudimentary knowledge elements recalled from secondary education and information elements absorbed from media and discussions in social settings to give explanations to the pre test questions. The number of life-world knowledge elements about the greenhouse effect are significant higher than about the ozone hole (t-test better than 0,5%-level). Like Dove (1996) we think this is because of the more uncertainty and complexity of the theory of greenhouse effect and global warming than ozone depletion and ozone hole. Dove's other idea for explanation (that the students link cause of ozone depletion to one single fact CFCs pollution) are more doubtful. Only 38% specify CFC pollution as cause of the ozone hole. In any case there is a great need for well designed instructions according to Boyes et al.(1995) and Dove's (1996) recommendations: We teach the two effects apart, and we try to engage in dialogue with our students to find out reasons for the life-world elements of knowledge (misconceptions).

It is difficult to find adequate information to make a comparison between OUC teacher students' knowledge on pre test with Norwegian lower secondary pupils (age 15/16). PISA (Programme for International Student Assessment, 2000) the last big international research projects with some relevant questions, used other test batteries. Pupils age 15 got an ozone question with 4 items. Pupils from United Kingdom scored significant better than the Norwegian on all four. This fact and the fact that the OUC teacher students score almost similar to Fisher's (2001) English 17+ on the same test, give some indication to the conclusion. The data give no support for rejection of the first hypothesis that before instruction our teacher students are on the same knowledge level as pupils in lower secondary school. We have to design our instruction programme accordingly.

The main curriculum goals for GEEO at OUC are to develop fundamental knowledge about greenhouse effect, climate, ozone problems and international environmental politics. Many students confused the two effects at pre test. That is why the two effects are "dissected and teased apart" (Boyes et al. 1995). The students got the instructions about radiation from the sun, the ozone layer, ozone depletion and ozone hole, human and biological problems from increased UV radiation and tropospheric ozone before Easter when Norwegian media are focused on ozone depletion, ozone hole, UV radiation, skin cancer, UV-filters, sun protection etc. Many Norwegian are skiing in the high mountains during Easter, with risking to be sun burned if not being aware of thin ozone layer and use of sun protection. 10 days later when returning to the College after Easter, the students started instructions about the greenhouse effect, climate, risk of climate change from global warming, national and international environmental politics.

Boyes et al. (1995) thought learning in this area could not be experimental. At OUC we think they are partly wrong. Our GEEO instructions are activity based – also with some experiments - developed and conducted in a social constructivist framework. Activities give us many opportunities to go into dialogue with our students "to find out reasons for the misconceptions and how best such ideas might be displaced." (Dove 1996). We think our activity based programme show what Leach and Scott (2002) wrote one year later:

'good teaching' will have certain characteristics

• teaching goals in a given topic area will be identified based upon an analyses of the learning demands of that topic;
• the classroom discourse will be lead and developed by the teachers in such a way that scientific knowledge is made available to students on the social plane of the classroom, and students are supported in reaching a personal understanding of that content (Leach and Scott 2002)

When the GEEO period started, we wanted each student to be aware of her/his own ideas and knowledge and the general confuse about greenhouse effect and ozone hole found on the pre test. To do that, the students got a condensed version of the answers on pre test. They were asked to during the period to mark out 'scientific knowledge' elements and decide how they could meet pupils with 'life-world knowledge' elements. At the end of the period we discussed with the students the knowledge elements from pre test which they thought were difficult to categorise.

During the period the students tried out a lot of other activities (many reported at last EWOC, Hansen 1999). 1.The activities are designed by the lecturers at OUC over years from "an analyses of the learning demands of that topic" (Leach and Scott 2002). Every single activity is a starting point of "the classroom discourse … lead and developed by the teachers" (ibid.). 2.The activities should be easy to adjust for use in compulsory school.

Like pupils in lover secondary school, some of our former students have had problems to keep the sources and effects of different gas pollution apart. Therefore the students from day one of the period should fill in a gas table with 'dangerous' gases one by one when they appeared in the instructions or texts. They should find out where the gas come from, the impact on the atmosphere, global/regional efforts against pollution, what could be done locally and how the pupils in compulsory school (and teacher students) could contribute themselves. All information was put together in a table:

The use of models and metaphors are well known in science and science teaching. The greenhouse effect is a metaphor first used in 1824 by the famous French mathematician and physicist Jean-Baptiste-Joseph de Fourier (1768-1830) to tell his science fellows what all is about. From our own teaching and research we know that pupils and students often have great problems with common used scientific models and metaphors. At pre test some take 'greenhouse' more ore less literary: "There is a greenhouse layer up in the atmosphere. The layer is like the glass roof of the greenhouse: Let the sunbeams come through and stop warmth [heat rays] from reaching out." (translation of typical answer). They have heard about the ozone layer and the effects from it, and perhaps think there also must be a layer making the greenhouse effect. In our instructions we tell our students: "Use your head! Your head is the earth. A knit cap is model when teaching about greenhouse effect and global warming. Sunglasses are models for the ozone layer. You see the difference?" The greenhouse effect take place from the ground and up – like the warming of the head from the cap. The ozone layer is fare from the head – like the sunglasses.

Experiments have long traditions in school science and in science teacher education. The rational for doing experiments have changed with changing learning theories. We do no longer think that pupils can learn very much science from imitation of scientific experiments or can prove scientific laws and theories. The theory of social construction of scientific knowledge implies:

An experiment is an opportunity for students to talk science together and for the lecturers to discuss that topic with them.

1.We have experienced from previous years that our students (like in media) often confuse reflection and absorption when talking about the greenhouse effect and the effects of the ozone layer. Perhaps the problem partly comes from missing conceptualisation of emission of heat (infra red radiation, IR) from bodies with normal temperatures. In order to avoid confusion, the students have to observe or do some very simple experiments showing the basic concepts of radiation:

Reflection: The lecturer demonstrates the reflection law with a mirror and a light (laser) beam. Afterwards the students check if the colours of the clothes of the neighbour student change when looking at her through a hand mirror. Conclusion: Reflection does not change colour (wavelength) of a light beam - only direction.

Absorption: The lecturer demonstrates absorption by piling clear glass plates or foils one by one on the overhead projector. When the students have observed the effect of absorption, we discuss where to find the light energy absorbed. Afterwards we use glass plates or foils in different colours. Conclusion: Absorption 'steels' light (energy) - the absorbent is warmed. (Later they experience how energy is absorbed by molecules and that some absorbent goes into chemical reactions.)

After these experiments, the students have to use the concepts 'reflection' and 'absorption' active when discussing the different colours of landscapes, oceans, clouds etc. on a satellite images of the earth.

Emission: The students look at visible light from a light bulb in a dark room, and feel invisible heat rays (IR) from a black hotplate by holding a hand one decimetre apart. Conclusion: 'Everything' emits radiation - even black bodies.

Now the students are able to discuss how land and ocean absorb some colours of visible light, get warmer and emit heat (IR) back. They have got the key to understand the greenhouse effect: The greenhouse gasses absorb the heat rays from the earth, get warmer and emit some energy back again (and some out to space).

The other small radiation experiments are note that adequate for this topic, but are done in order to complete the picture of the physics of electromagnetic radiation:

Refraction: The lecturer makes a spectrum of white light with a glass prism, and talk with the students about the colours in white light and sunrays. This is an opportunity to talk more about the electromagnetic spectrum as an energy spectrum from IR to ultra violet (UV) and introduce the idea of photons as energy packages.

Scattering: Could easily be demonstrated by dripping some milk into a glass of water. The students observe the 'clouds' and discuss why clouds are white or grey. Then stir and set a light bulb behind the glass. When using skim milk they can see 'the blue sky' and 'a red sunset'.

If the students later in the GEEO course are using the basic concepts in a wrong way, we can refer to the experiments. The following experiments are intended to illustrate some special phenomenon or effects. Some experiments could be done by students in pairs. Some experiments are better demonstrated by the lecturer.

2.Pour soda water in two test tubes. Set one in a hot bath (hot tap water) and the other in a cold bath. Watch what happen to the soda water.

This experiment illustrates that warmer oceans will release more dissolved carbon dioxide to the atmosphere than cold oceans do. This is an opportunity to discuss what could happen if we are getting a warmer climate with warmer oceans. What about the carbon cycle? What about feedback on the greenhouse effect if releasing more carbon dioxide to the atmosphere or less uptake in the oceans?

3.Put an ice block in a water bath. Let the students make hypothesis about the water level when it melts. Ask: "Will it be higher, lower or steady state?"

This experiment shows that melting ocean ice does not change ocean level. Since the ice is floating, the water from melted ice fits perfect into the 'hole' the ice made in the ocean (Archimedes'). Many students tell that they made a false hypothesis. In the media they have noticed catastrophic scenarios from raising sea level caused by melting ice from the Poles, but have not understood that it is a great difference between the North Pole's ocean ice and the South Pole's ice cap. This experiment is also an opportunity to discuss with the students if a melting ice cap in Antarctic is a plausible scenario. A warmer climate would accelerate the water cycle in general. This might cause more snow in Antarctic with an increasing ice cap and sinking ocean level as result.

4.Examine thermal expansion: Fill a test tube with coloured water. Put on a rubber cap with a glass tube. Place it in a hot bath. The question is again: "What do you think are going to happen?"

This time the students' hypothesis was better. This experiment should illustrate that a warmer climate will result in warmer oceans and thereby thermal expansion causing ocean level rise. Now we discuss with the students who will suffer from this effect, and what could be done to mitigate the problems. This could also be a place to discuss who are going to pay the cost of mitigation: the countries threatened by raising ocean level, the industrialised nations responsible for the release greenhouse gases or the international community?

5. Examine the real greenhouse effect: Look at the sun through a glass sheet. Then hold the glass sheet between a hotplate and your hand.

The experiment shows that visible light from the sun passes through glass, but heat rays (IR) are absorbed by glass in the greenhouse - like greenhouse gases do in the atmosphere. This illustration of the physical basis of the metaphor 'greenhouse effect' is the opportunity to once again repeat: there is no 'greenhouse layer' up in the atmosphere like the glass roof in the greenhouse. The greenhouse gasses are mixed into the atmosphere from the ground and up.

6. Water molecules (H₂O) and other greenhouse gas molecules in the atmosphere are set in rotation or vibration by absorbing IR rays i.e. absorbing the energy in a IR photon. The energy is spread around by collision between air molecules. This increasing kinetic energy on micro level is a warmer atmosphere on macro level. This micro level process could be demonstrated by students' acting in a role-play: one O-student hold one H-students in each hand. They start rotating or vibrating if they get an 'IR-flash' (IR photon) from the lecturer.

7.The micro processes going on when 'building' O₃ (ozone) molecules in the atmosphere from 40km and upwards, could also be demonstrated through role play: O₂ (two bound O students) are split when absorbing a high energy UV photon ( λ<242,4nm). Each of the single O atoms reacts with an O₂. We become two O₃ made from three O₂ by absorbing UV. (Down to 12km the opposite process take place: O₃ molecules are split by UV and visible light into O and O₂. O reacts with one O₃ to two O₂. The processes of building and splitting ozone result in absorbing all UV λ<290nm (UVC) and a good portion of 290< λ<320nm (UVB) from the sun. The rest of UVB and UVA (320< λ<400nm) goes right through the atmosphere like visible rays do.) This role-play together with more information about the physical and chemical ozone processes in the stratosphere is start of the discussion of why the ozone layer is situated between 15km and 25km.

8.Make a fair test of sun-milks with different UV-filters. Rub different squares of a foil with different sun-milks. Pin it to the wall with a white sheet behind it. Blackout windows and dim the light. Use light from an UV-lamp at the foils. Look at different absorption in the sun-milks i.e. different blackening of the white sheet.

After concluding the experiment, we discuss why skin cancer are increasing in Norway? Is it because of ozone depletion, less use of UV-protection, our life style or …. ?

During the GEEO instruction period the students had to make a written documentation and evaluation of one of the experiments they have done.

Project-based learning of atmospheric pollution, using all sorts of sources and presentations, happens to be successful. It is labour-intensive, but could develop deep knowledge in a wide context. The project method was not used in GEEO, but in another topic.

When the greenhouse effect and the effects of the ozone layer are on the agenda media give a lot of information, but of variable quality. The students collected newspaper articles for the 'class library' from start of the academic year. These articles have been used in the instructions and discussions. TV programs have also been used same way. Goals for the work are both to develop deeper understanding of GEEO and critical attitudes towards media information.

The second written report was evaluation of a newspaper article, an Internet site, a TV program or other relevant media information.

On the Internet the two effects are always on the agenda. The findings was used in the same way as media stuff. The students could use our special resource site for GEEO with many links or they could browse on the web.

Formerly our students used a PC-program based on a simple climate model where they could simulate release of greenhouse gasses from different agents and look at global warming as effect. This program look old fashion and was not used this time. We hope to have more modern PC or CD programs where the technology from PC-plays is used to make good simulations and decision programs.

The students made a "Panel-debate on TV". The agenda was "Global warming and a hole in the ozone layer. What to do?" The students worked in groups of 7-8, all given the same general written briefing. Each members of every group made deeper specialist briefing for their role: Chairperson, Greenhouse-expert, Ozone-layer-expert, Environment-activists promoting "action-now" and Politicians or Businessmen promoting "wait-and-see". At the end of the period one group by draw acted in plenum as a panel and the rest of the students acted as an audience asking questions. The role play is a powerful method to couple factual knowledge with development of interests and values in conflicting problems.

An optional ending of the GEEO period has often been quiz. Each student works out many questions and answers. Groups of 3 or 4 fight against each other in a cup system ending up with the final and a winning group.

The students' assessment of the activities is all over positive. They mean that teachers could use the activities, with small adjustments, in grade 10 compulsory school where the relevant goal in science is: "Pupils should have the opportunity to learn about the greenhouse effect and the effects of the ozone layer" (C10 1999)

The post test questions are similar to the pre test which the students have had opportunity to work with during the hole DEEO period as a learning activity. Some have done, other have not, but nobody knew that they were going take a post test the last day i.e. nobody could prepare themselves specially for the post test.

Only 22 students were present at post test. All 22 students distinguish between increased and normal greenhouse effect and/or write that the greenhouse effect is essential for life on earth. Everyone can name one or more greenhouse gas and 68% explain the greenhouse effect in detail. Life-world elements of knowledge are very rare.

Few students (table 2,3) mix elements of scientific knowledge and life-world knowledge. The most frequent (≥3) combinations are 5-0, 5-1 and 6-0 scientific and life-world elements respectively. This clustering counts all together 55%. The variation is lower than at the pre test. 64% students have 0 life-world elements. 2 life-world elements are the highest number (only 5%). The average is 5,73 scientific and 0,41 life-world elements.

The increase from average 3,11 to 5,73 scientific knowledge elements and the decrease from 2,51 to 0,41 life world elements are both significant (t-test better than 0,5%-level). In statistical theory t-test for significance shall only be used on random samples, so the results must only be taken as a strong indication of improvement.

All students think the ozone hole is harmful. Now most (86%) students link the ozone hole to the South Pole or Antarctic. In spite of that fact all but one mention one or more effect of increased UV radiation that hardly can happen in Antarctic for instance skin cancer (sunbath is very rare there). They have returned to talk about effects of the worldwide ozone depletion. No students have elements showing that they think that hole in ozone layer causes the greenhouse effect and/or global warming. Only 9% think that CO₂ pollution of the atmosphere more or less causes the depletion of the ozone layer or the ozone hole.

Very few students (table 4, 5) mix elements of scientific knowledge and life-world knowledge. The most frequent (≥3) combinations are 5-0, 6-0, 7-0 scientific and life-world elements respectively. This clustering counts all together 55%. The variation is lower than at the pre test. 64% have 0 life-world elements. 3 life-world elements are the highest number (only 9%). The average is 5,32 scientific and 0,5 life-world elements.

The increase from average 3,24 to 5,32 scientific knowledge elements and the decrease from 1,59 to 0,55 life world elements are a strong indication of improvement (significant, t-test better than 0,5%-level).

Only 22 students were present at the post test. We also have to keep in mind that the test was taken the last day of the period, not two - three weeks later which is normal in this test design. I.e. the external validity could have been much better. There seems, however, to be strong indications for improvement of knowledge and facts from pre test (figure 1). The confuse of greenhouse effect and ozone hole is reduced to zero. Everyone differentiate between increased greenhouse effect that might cause global warming and normal greenhouse effect which is essential for life on earth. Most students give a scientific explanation with some details of both effects, change in the effects caused by anthropogenic pollutions, and the influence on earth and life. The improved knowledge is due to a combination of participating in activities, instructions, lectures and the students' work with the literature and web sites. Some students have followed every lecture, activity and instruction, while others were hardly seen during the period – and perhaps not on the tests.

The exam was three weeks after post test. 45 students chose to answer the exam set of questions where greenhouse effect was the red thread. The time limit was 4 hours.

Question 1a

All 45 students gave a satisfactory explanation of the greenhouse effect and made a broad discussion of the anthropogenic carbon dioxide (CO₂) pollution. The more peripheral aspects are often forgotten (or unknown). This could be due to the exam situation and open-form questions. Such questions put the students in the position to recall and chose adequate knowledge among all knowledge and facts. 58% knew that human activities like some special industries and leakage from old refrigerators could result in chlorine fluorine carbon (CFC) pollution. Only 33% discussed the more obvious methane (CH₄) pollution from for instance coal mining, oil industry, garbage heaps, waist disposal sites and rice fields. 7% mentioned dinitrogen-oxide (laughing gas, N₂O) pollution from use of artificial fertilisers. 4% mentioned how nitrogen oxides (NOXs) exhausted from combustion engines could result in formation of ozone (O₃) in the troposphere. The most important greenhouse gas water vapour (H₂O) was discussed by 40% who did not forget to emphasize that human activity give very little contribution to atmospheric vapour level compared to evaporation from the oceans.

Average score is 54,7% (full score 100%) and standard deviation is 9,6.

Question 1b

All students could describe some changes in oceans caused by global warming. Most write about the worldwide ocean level raise caused by thermal expansion. They remember that sea ice can melt without direct influence on the ocean level – only on salinity. Some tell that the oceans' ability to take up carbon dioxide decrease with increasing temperature with a positive feedback as result. Some write that the ocean currents and thermohaline formation of the deep ocean water can be influenced due to change in temperature and salinity ("may the Gulf Stream stop?"). Some students remember that some of the changes could result in new ecological conditions, that warmer oceans cause changes in the hydrological cycle, etc.

Average score is 53,0% and standard deviation is 19,3. The variation in the sample is much greater than on 1a, perhaps because of many different and complex subjects to recall under exam stress.

Question 2

All students knew something about one or more environmental negative consequence like drought, heat waves, increased precipitation, dramatic weather episodes, flooding etc. in regions with developing countries.

Average score is 47,7% and standard deviation is 14,1. The great variation reflects different ability to remember many consequences and to discuss them which is more then just mention them.

In the next part they should focus on negative consequences for the people and the whole society in developing countries. Most students could to some degree discuss how changed environmental conditions could influence on occupations like agriculture and fisheries, and on buildings, infrastructure etc.

Average score is 50,0% and standard deviation is 6,4.

The students' ability to take in developing theories (strategies, models etc.) in the discussion is not a part of this investigation.

Question 3.

All students could point out one particular conflict subject. The chosen examples of teaching strategies used to raise pupils awareness in such perspectives reflects what the students have experienced themselves in the instructions in GEEO or other NSE subjects: group work, project work, debate, role play like 'climate conference', consensus conference (Kolstoe 2000), investigation with questionnaire, information from extern specialist etc.

Average score is 63,0% and standard deviation is 14,6. On this question many answers are very good and above the average standard on exams. Very few have significant shortcomings. The score is better than on Question 1 and 2. This is not surprising since another main subject on the teacher programme is Educational Theory and Practice (30 credits).

The exam questions are fare more complex than the pre and post test questions. Most students are able to use scientific knowledge when they explain why human activity can cause global warming, describe changes in the oceans and discuss negative consequences for environment and people in developing countries. All students could give a scientific explanation of the greenhouse effect, a fact that confirms the conclusions from post test. Only one of 45 students failed to pass the exam.

A weakness of this study is the reduced external validity caused by low and not random participation on pre test and in particular on post test. The results of the investigations are, however, so clear that it seems like neither of the research hypothesis have been falsified. Before starting the Nature, Society and Environment studies at Oslo University College many student teachers seem to be at almost the same knowledge level about the greenhouse effect and the effects of the ozone layer as pupils in lower secondary school. They use perhaps more 'scientific' knowledge elements and less 'life-world' knowledge elements in their answers, but like pupils the student teachers mix elements of the 'two worlds of knowledge' together. Some even confuse greenhouse effect and ozone depletion. The lecturers at the College have for years tried to analyse the learning demands based upon students' 'pre knowledge' and the teaching goals in our curriculum in a social construct framework. From the analysis we have designed an activity based teaching programme with many opportunities to go into dialogue or discussions in small and bigger groups. The learning from activities are supported by ordinary lectures. Post test after the instructions indicates that most students have decreased substantially the mix of knowledge elements in favour of an increased number of 'scientific' knowledge elements. This is confirmed in the more valid exam which also shows that all students have developed a broad spectre of knowledge about the global warming problem for environment, people and societies. Most students show general good ability to use such knowledge in different contexts. Their teaching skills are not fully realistically tested on exam, but their ability to plan teaching seems to be reassuring. To conclude: there are good indications that the majority of our teacher students are well prepared for teaching about the greenhouse effect and the effects of the ozone layer in compulsory school.

Boyes, Edward and Martin Stanisstreet (1992): Students' Perceptions of Global Warming. International Journal of Environmental Studies, vol.42

Boyes, Edward and Martin Stanisstreet (1993): The 'Greenhouse Effect': children's perceptions of causes, consequences an cures. International Journal of Science Education, Vol.15, No.5

Boyes, Edward, William Chambers and Martin Stanisstreet (1995): Trainee Primary Teachers' Ideas about the Ozone Layer. Environmental Education Research, vol.1, no.2

Cicerone (2001): De fattigste rammes hardest av klimaendringer [Climate change is worst for the poor]. Center for International Climate and Environment Research (CIERO) nr.1 mars 2001. www.cicero.uio.no

Dove, Jane (1996): Student Teacher Understanding of the Greenhouse Effect, Ozone Layer Depletion and Acid Rain. Environmental Education Research, vol.2, no.1

Fisher, Brian W. (1998a): There's a hole in my greenhouse effect. School Science Review, vol.79, no.288

Fisher, Brian (1998b): Australian students' appreciation of the greenhouse effect and the ozone hole. Australian Science Teachers' Journal, vol.44, no.3

Fisher, Brian (2001): The Study of the Atmosphere in Science Education. Dissertation, Meteorological Publications. www.brian.fisher.btinternet.co.uk/

Hansen, Pal J. Kirkeby (1999): Greenhouse effect and the effect of the ozone layer. I 5^th International Conference on School and Popular Meteorological and Oceanographic Education. Preprint volume, Australian Meteorological and Oceanographic Society, p.66f + 6 posters presented at the conference Education: Weather, Ocean, Climate (EWOC), Ballarat and Melbourne 5-9 July 1999

Kolstoe, Stein Dankert (2000): Consensus projects: teaching science for citizenship. International Journal of Science Education, vol.22, no.6

Leach, John and Phil Scott (2002): Individual and sociocultural views of learning in science education. Accepted for publication to Science and Education.

PISA (2000): Programme for International Student Assessment. www.pisa.oecd.org/

Solomon, Joan (1993): The social construction of children's scientific knowledge. In Paul J. Black and Arthur M. Lucas (red.): Children's informal ideas in science. Routledge, London

The curriculum for the 10-year compulsory school (C10 1999), The Royal Ministry of Education, Research and Church Affairs, Oslo. http://www.ls.no/L97/L97_eng/

WMO (2001): The IPCC Third Assessment. World Climate News, World Meteorological Organization. June 2001 No.19, 7-10. www.wmo.ch