Conceptions of the Greenhouse Effect and Global Warming among Elementary Students from Diverse Languages and Cultures

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1 Conceptions of the and Global Warming among Elementary from Diverse Languages and Cultures Okhee Lee Benjamin T. Lester Li Ma Julie Lambert Melissa Jean-Baptiste ABSTRACT As part of a large-scale intervention, this study examined conceptions of the greenhouse effect and global warming among elementary students from diverse languages and cultures in the U.S. To make science relevant and meaningful for diverse student groups, the intervention emphasized the integration of (a) scientific understanding and inquiry, (b) English language and literacy, and (c) students' home language and culture. The study involved 5th grade students from five elementary schools of varying demographic makeup in a large urban school district. The intervention's effectiveness was measured by student responses on a writing prompt addressing this topic in the beginning and at the completion of instruction over the school year. The results indicate that students overall demonstrated more scientific conceptual understandings after instruction. Furthermore, all demographic subgroups in terms of gender, ethnicity, socioeconomic status, English proficiency, and home language demonstrated statistically significant improvements after instruction, with the exceptions of African-American and Haitian students showing little or no gain. INTRODUCTION AND BACKGROUND There exists much debate on the nature, cause, and resolution to the problem of global warming in the U.S. and abroad. ' alternative conceptions interfere with their understanding of scientific conceptions of the greenhouse effect and global warming (Boyes and Stanisstreet, 1993, 1998). Furthermore, these phenomena are so complex that students continue to express alternative conceptions and experience difficulties even after educational interventions (Mason and Santi, 1998; Rye et al., 1997). This study examined scientific and alternative conceptions of the greenhouse effect and global warming among 5th grade students from diverse languages and cultures in the U.S. The study was conducted as part of an instructional intervention (consisting of an inquiry-based science curriculum and teacher professional development) that was aimed at promoting elementary students' understanding of Earth and its characteristics and processes. To make science relevant and meaningful for diverse student groups, the intervention emphasized the integration of (a) scientific understanding and inquiry, (b) English language and literacy, and (c) home language and culture. It was not a primary goal of the research to examine students' School of Education, University of Miami, P.O. Box , Coral Gables, FL School of Education, University of Miami, P.O. Box , Coral Gables, FL School of Education, University of Miami, P.O. Box , Coral Gables, FL Florida Atlantic University, 777 Glades Road, P.O. Box 3091, Boca Raton, FL School of Education, University of Miami, P.O. Box , Coral Gables, FL conceptions about every lesson topic. However, the prevalence of students' alternative conceptions regarding the greenhouse effect and global warming within their writing samples led us to a more systematic investigation. Prior to and following the intervention over the school year, students responded to a writing prompt on the greenhouse effect and global warming. Thus, students' written responses constitute the core dataset used to examine change in their scientific and alternative conceptions of this topic. LITERATURE REVIEW The greenhouse effect is "the result of chemical compounds found in the Earth's atmosphere acting as greenhouse gases, trapping outgoing terrestrial radiation and warming Earth's atmosphere" (Environmental Protection Agency, 2002, p. 2). These primary greenhouse gases-water vapor, carbon dioxide, and methane-occur naturally. However, human activity, particularly since the late 19th century, has contributed to an increase in the amount of certain atmospheric gases (i.e., carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons) (American Geophysical Union, 2003; Environmental Protection Agency, 2002; Intergovernmental Panel on Climate Change, 2001). Thus, the greenhouse effect is a naturally occurring phenomenon, whereas an intensified greenhouse effect refers to the acceleration or magnification of this phenomenon as a result of human activity. Global warming refers to an increase in global average temperature, and is hypothesized to result from an intensified greenhouse effect. coneptions of the greenhouse effect and global warming - The literature addressing students' conceptions about the greenhouse effect and global warming can be organized into two categories: (a) without an educational intervention and (b) in the context of an educational intervention. Studies involve students ranging from late elementary to secondary school, and to first- and second-year student teachers. ' conceptions without an educational intervention - Boyes and Stanisstreet (1993) investigated conceptions of the greenhouse effect (i.e., causes, consequences, and possible cures of global warming). In all, 861 secondary school students (ages between 11 and 16) in the U.K. completed the questionnaire, and 60 randomly selected students participated in semi-structured interviews. The majority of students correctly noted that an intensified greenhouse effect Lee et al. - Conceptions of the and Global Warming 117

2 would result in the Earth getting hotter (i.e., global warming) leading to changes in weather patterns. The most prevalent alternative conception involved was the chain of ideas-the depletion of ozone layer allows a higher penetration of solar ultraviolet (UV) rays to the Earth, which causes the Earth to get warmer and an increase in skin cancer. Frances et al. (1993) replicated the Boyes and Stanisstreet study (1993) with 563 elementary school students between the ages of 8 and 11 in the U.K. This study focused specifically on actions to reduce global warming. identified a range of actions, correctly or incorrectly, to reduce global warming. confused two major environmental problems-global warming by an intensified greenhouse effect and ozone layer depletion. Dove (1996) studied how well university students understood both the greenhouse effect and ozone layer depletion. The study involved 60 first- and second-year student teachers in the U.K., who completed paper-and-pencil tasks including some open-ended questions. The results mirrored the outcomes of previous studies including elementary and secondary school students. The abstract subtleties of complex environmental phenomena, such as global warming and ozone layer depletion, were difficult to distinguish and comprehend even for adults. Given the prevalence of the fusion of global warming and ozone layer depletion found in previous research, Boyes, Stanisstreet, and colleagues conducted a series of studies to examine students' conceptions of these two environmental issues. Boyes and Stanisstreet (1997, 1998) studied 13 and 14 year-old high school U.K. students, and Boyes et al. (1999) included Greek high school students between the ages of 11 and 16. The results of these studies indicate consistent patterns in students' conceptions. The majority of students correctly believed the ozone layer was the primary mechanism for allowing UV rays to reach the Earth. However, many students incorrectly believed an intensified greenhouse effect was the reason for increase in UV rays. Many also incorrectly identified the increase of the Earth's temperatures (i.e., global warming) as a cause of skin cancer. Koulaidis and Christidou (1998) investigated models of Greek students' conceptions of the greenhouse effect. The study involved 40 elementary students at grades 5 and 6 (11 to 12 years of age) using semi-structured interviews to examine their views of the causes, processes and mechanisms, and consequences of the greenhouse effect. ' views were categorized based on three criteria, including issues of greenhouse gases, the connection between the greenhouse effect and ozone layer depletion, and the connection between types of radiation and the greenhouse effect. Children's models involved a common core of beliefs-the greenhouse effect is due to solar radiation that heats up the earth and the atmosphere, while getting trapped by certain atmospheric gases, and severely changes the climate, melts the polar ice, and raises the sea level. Andersson and Wallin (2000) investigated Swedish students' understanding of the greenhouse effect, the societal consequences of reducing CO2 emissions, and the problem of ozone layer depletion. Data were collected by administering open-ended written tasks to 423 students in grade 9 (15-16 years old) and grade 12 (18-19 years old). In addition to the difficulties understanding the greenhouse effect, students did not fully understand the magnitude of societal change as a result of aggressively reducing CO2 emissions and confused ozone layer depletion with the greenhouse effect. ' conceptions in the context of an educational intervention - Mason and Santi (1998) investigated Italian elementary students' conceptions of the causes, consequences, and remediation of the greenhouse effect and global warming. The researchers used socio-cognitive interactions (i.e., support for verbal explanations and critical evaluations of different points of view) to promote conceptual change learning with 22 fifth grade students, between 10 and 11 years of age, during the implementation of an environmental education curriculum unit throughout a school year. All the lessons were audio-recorded and transcribed, and each student was interviewed prior to and after completion of curriculum implementation. The researchers concluded that as a result of collaborative discourse and reasoning, students were able to "build new knowledge based on revision of their personal conceptions and beliefs" (p. 82). Rye et al. (1997) studied conceptions of global warming held by 24 American middle school students, grades 6 through 8, following their completion of a global warming unit based on the sciencetechnology-society (STS) approach. Standardized open-ended interviews were conducted with the students after completion of the unit; however, pre-instruction interviews were not conducted. Based on the analysis of students' concept maps, about one-half of the students maintained the alternative conceptions that ozone layer depletion is a key cause of global warming and that carbon dioxide destroys the ozone layer. Summary - Based on consistent results about alternative conceptions of the greenhouse effect and global warming from elementary to college students primarily in European countries, Koulaidis and Christidou (1998) concisely summarize the results as follows: These common elements include: (a) the tendency to confuse the greenhouse effect with the ozone depletion, or to causally attribute the former to the latter; (b) the tendency to understand and interpret the greenhouse effect exclusively as an environmental problem, ignoring the fact that it is the result of a natural mechanism; (c) the tendency to attribute the greenhouse effect to specific gases over others; or (d) the reference to specific consequences of the man-made greenhouse effect, such as an increase in the planet's mean temperature and sea level. (p ) Much of the existing literature examines students' conceptions without an educational intervention. Whereas most of the studies have been conducted in European countries, there is little research involving U.S. students (Rye et al., 1997). Additionally, no study examining students' conceptions among demographic subgroups is found in the literature. Thus, there is a need to design effective interventions to help students from diverse backgrounds change their alternative conceptions into more scientifically accepted conceptions. Purpose of the study - This study examined 5th grade U.S. students' responses to a writing prompt about the greenhouse effect and global warming. The prompt 118 Journal of Geoscience Education, v. 55, n. 2, March, 2007, p

3 Figure 1. Map of concepts related to the greenhouse effect and global warming asked students to write about the problem, cause, and effect. While responding to the prompt, students volunteered solutions to the problem, though this was not explicitly requested in the prompt. Comparing students' conceptions prior to and following our intervention over the school year, the study examined three research questions: (1) What were students' conceptions regarding the greenhouse effect and global warming? (2) Did students' conceptions change after participating in the intervention? and (3) Were there differences among demographic subgroups based on gender, ethnicity, socioeconomic status (SES), English to Speakers of Other Languages (ESOL), and home language? METHOD Research context and participants - The study was conducted in a large urban school district in the southeastern U.S. with a highly diverse student population. During the school year the ethnic makeup of the student population was 59% Hispanic, 29% Black (including 7.4% Haitian according to the district data on students' home language), 10% Non-Hispanic White, and 2% Asian or Native American. Within the school district, 70% of the elementary students participated in free or reduced price lunch programs and 24% were designated as limited English proficient (LEP), which is the term used by the state. This study involved 611 fifth grade students at five elementary schools. Two schools served predominantly Hispanic students (94% and 89% respectively). Many of the students at the first school were newly arrived or first-generation immigrants (45% LEP) and from low-ses homes (81% of students received free or reduced price lunch), while most of the students at the second school were U.S. born (15% LEP) and from low to middle-ses homes (50% free or reduced price lunch). The third school served predominately Haitian and African-American students (90%), with 22% of students designated as LEP and most from low-ses homes (99% free or reduced price lunch). At the two remaining schools, most of the students were native English speakers (4% and 3% LEP) of White, Hispanic, or African-American descent and were from middle-ses homes (20% and 21% free or reduced price lunch). Instructional intervention - The overall goal of the larger research was to articulate academic disciplines (e.g., science) with students' linguistic and cultural experiences to make the academic content and practices accessible, meaningful, and relevant to all students (Lee, 2004; Lee and Fradd, 1998). This integration served as a conceptual and practical guideline for instructional materials development, teacher professional development, and classroom practices. Curriculum unit - The Living Planet unit was developed by scientists as well as educators with expertise in students' home languages and cultures to make the unit relevant and meaningful for students from diverse backgrounds (for details, see Lambert et al., in press). The unit provides students with an introduction to the Earth as a planet of different interacting cycles and systems (atmosphere, biosphere, geosphere, and hydrosphere). Major topics included in the 12 lessons in Lee et al. - Conceptions of the and Global Warming 119

4 the unit are the solar system, Earth's seasons and climate, plate tectonics, the rock cycle, ocean currents, ecosystems, Earth's resources, and endangered species. Many of the lessons include having students view an eco-public service announcement. As a culminating lesson and assessment on the unit, students present a plan for developing an imaginary island at a specific location on Earth. In the lesson on the greenhouse effect and global warming, students investigate the relationship between carbon dioxide in the atmosphere and a planet's surface temperature through a simple activity. place sand and a thermometer in each of two plastic containers. After heating both containers with a lamp, one of the containers is covered to represent a planet with an atmosphere of carbon dioxide and the other is left uncovered to represent a planet without an atmosphere. record the temperature in each container as it cools. The container with the cover, on average, cools less. The activity provides a simple representation of an environment with and without a greenhouse effect. In the second activity, students compare the Earth's temperature and the amount of carbon dioxide in the atmosphere over the last century. are asked to graph the global average temperature for each decade and the amount of carbon dioxide in the atmosphere from 1910 to As a culminating activity of the lesson, students view "The Perfect Balance," an eco-public service announcement about global warming produced by the Earth Communications Office (oneearth.org). After viewing the announcement, students are asked to write a public service announcement to teach the public about global warming. A concept map illustrates the connections of the prerequisite concepts needed to understand the larger idea of global warming throughout the unit (see Figure 1). Teacher professional development - All teachers attended four full-day workshops on regular school days throughout the year. At the first three workshops, teachers engaged in all of the lessons. The topic of the greenhouse effect and global warming was included during the second workshop. At the final workshop, teachers shared examples of how they had modified specific lessons for use with their own students and incorporated English literacy development and students' home language and culture into science instruction. Using the lesson on the greenhouse effect and global warming described above, teachers learned the science content, engaged in inquiry activities, and shared ideas about teaching strategies. Additionally, teachers discussed how to draw upon students' cultural experiences and home language in science instruction. For example, students from South America were familiar with measuring temperature in degrees Celsius rather than degrees Fahrenheit. The eco-public service announcement about global warming showed how individuals are all connected to their communities and to one another in a global sense, and also encouraged discussion about students' cultural backgrounds and experiences. Classroom instruction - Participating students and teachers were provided with complete sets of materials, including teachers' guides, student booklets, science supplies, and trade books. Instruction started in mid-october, but there was a lull from January through mid-march due to preparation for the statewide assessments in reading and mathematics. Although duration of instruction varied across the classrooms, students completed the unit by the end of the school year. The specific lesson on the greenhouse effect and global warming took approximately two weeks of instruction, assuming two or three hours of science instruction per week. DATA COLLECTION AND ANALYSIS Data collection - were asked to respond to a writing prompt about the greenhouse effect and global warming prior to and after instruction of the unit. Many scientists believe that Earth's climate is warming due to an intensified greenhouse effect. Pretend you are a scientist and have been asked to write a radio announcement about your concerns. Describe to the listeners what an intensified greenhouse effect is, reasons that the amount of greenhouse gases in our atmosphere is increasing, and possible consequences of a warmer climate on Earth, especially for the region where you live. Teachers were asked to follow standard procedures for administration of the writing prompt. They were advised to read the prompt for students with reading difficulties and to translate it for ESOL students. ESOL students were allowed to write their answers in either English or in their home language, although only a small number of students wrote in Spanish (10) or Haitian Creole (3). There was no time restriction for completion of writing. Data analysis - Writing samples of those students who completed both pre- and post-instruction assessment were included for analysis, for a total of 420 students and 840 writing samples. All the writing samples were coded using the scoring rubrics for scientific and alternative conceptions (and the rubrics are available from the authors upon request). These rubrics were developed on the basis of two sources including (a) the instrument used by Boyes and Stanisstreet (1993) and (b) the science content on this topic presented in the unit. Both rubrics contained five components: (a) definition of the greenhouse effect, (b) definition of an intensified greenhouse effect, (c) cause of an intensified greenhouse effect, (d) consequences of an intensified greenhouse effect, and (e) actions to reduce global warming. It was relatively clear to determine students' scientific conceptions. In contrast, it was more difficult to identify students' alternative conceptions systematically because writing samples often included irrelevant or tangentially relevant responses. The ambiguity of coding student responses raised questions about reliability. Thus, quantitative analysis was conducted only with regard to scientific conceptions. With regard to alternative conceptions, students' writing samples were analyzed qualitatively in terms of major themes. In coding scientifically correct responses, each writing sample was used as the unit of analysis, i.e., when the same idea was repeated, it counted as one correct response. After inter-rater agreement between two raters (the second and third authors of this paper) was established at 90%, the raters completed coding independently. For each component, the total frequency of correct responses and the total number of students 120 Journal of Geoscience Education, v. 55, n. 2, March, 2007, p

5 Component Pre-Instruction Post-Instruction Definition of the Explanation of an Intensified Causes of an Intensified Possible Consequences of an Intensified Human Actions to Reduce Gas Emissions giving correct responses, respectively, were obtained in the beginning and at the completion of instruction. To examine change in students' conceptions in the sample, the numbers of students giving correct responses between pre- and post-writing samples for each component were analyzed using Wilcoxon T tests for two matched samples. Similarly, to examine differences among demographic subgroups, the numbers of students giving correct responses between pre- and post-writing samples for all five components combined were analyzed using Wilcoxon T tests. Given the large sample size and the multiple tests, the significance level was set at <.01. RESULTS Correct Statement (Frequency) 1. gases trap heat (21) 2. Temperature balance (8) 1. Increase in Earth s temperature (26) 2. Bad for the Earth (5) 3. Trees burned or cut down (5) 1. Fossil fuels (17) 2. Generic pollution (10) 3. Trees burned or cut down (5) 1. People die (36) 2. Habitats and ecosystems change - plants die (35) 3. Weather or climate too hot/cold (28) 4. Animals could die (25) 1. Reduce pollution - burning of fossil fuels (12) 2. Reduce car use (7) 3. Save and plant trees (3) 4. Conserve/Save energy (3) Total Frequency The results are presented with regard to the three research questions: (a) students' conceptions, (b) changes in students' conceptions for the sample after the intervention, and (c) differences in students' conceptions among demographic subgroups. ' conceptions - Since the existing literature provides specific information about students' conceptions on this topic, the results here do not present detailed analysis of students' scientific or alternative conceptions. Instead, general patterns in students' conceptions are described below. Total Number of Scientific conceptions - The results regarding the total frequency of correct responses and the total number of students giving correct responses are presented in Table 1. Since each student could give one or more correct responses, the total frequency of responses would be higher than the total number of students. The results Correct Statement (Frequency) 1. gases trap heat (21) 2. Temperature balance (37) 1. Increase in Earth s Temperature (23) 2. Bad for the Earth (9) 3. Human activity (8) 1. Fossil fuels (61) 2. Generic pollution (42) 3. Trees burned or cut down (22) 1. Glaciers melt and sea levels rise (84) 2. Weather or climate too hot/cold (41) 3. People die (41) 4. Habitats and ecosystems change - plants die (33) 1. Save and plant trees (29) 2. Reduce pollution - burning of fossil fuels (19) 3. Reduce car use (13) 4. Recycle (13) Total Frequency Total Number of Total Table 1. Scientific conceptions: frequency of correct responses and number of students giving correct responses. Note the correct statements in this table indicate common responses, and do not represent an exhaustive list of responses. indicate three main patterns in student responses. First, common responses about the definitions of the greenhouse effect and an intensified greenhouse effect, as well as causes of an intensified greenhouse effect, were similar in the beginning and at the completion of instruction. At both points in time, students tended to give definitions in terms of greenhouse gases trapping heat and the Earth's temperature rising, which is caused by burning fossil fuels and depleting forests. In contrast, common student responses for the consequences of an intensified greenhouse effect and actions to reduce it were noticeably different. For example, in the beginning of instruction, students described the consequences in terms of people or plants dying, whereas they expressed more scientific understandings in terms of glaciers melting, sea levels rising, and climate changing after instruction. Second, the ratio of the total frequency of correct responses and the total number of students giving correct responses for each component indicates that, on average, one student gave one correct response, with the exception of consequences for which one student gave two correct responses. Overall, in the beginning of instruction, a total of 171 out of 420 students in the sample (41%) gave a total of 340 correct responses (2 correct responses per student). At the completion of instruction, a total of 286 out of 420 students in the sample (68%) gave a total of 730 correct responses (2.5 correct responses per student). Finally, the numbers of students indicating scientific conceptions varied among the five components. Even in the beginning of instruction, many students had a greater understanding of consequences, compared to the remaining four components. continued to have Lee et al. - Conceptions of the and Global Warming 121

6 Component Pre-Instruction Post-Instruction Definition of the Explanation of an Intensified Causes of an Intensified Possible Consequences of an Intensified Human Actions to Reduce Gas Emissions (in the literal sense) The greenhouse effect is the ozone layer When the ozone layer is getting worse Oxygen traps sunrays Earth is getting closer to the Sun Increase in plants Holes in the ozone layer Skin cancer Bad sunburn Not enough oxygen Volcanoes and earthquakes Turns on the AC Use suntan lotion (in the literal sense) The greenhouse effect is the ozone layer When the ozone layer is getting worse Oxygen traps sunrays Holes in the ozone layer Skin cancer Bad sunburn Not enough oxygen Volcanoes and earthquakes Turn on the AC Stop building greenhouses Use suntan lotion Table 2. Alternative conceptions: major themes in student responses. Note This table presents common responses which account for over 80% of responses for each component. Component Definition of the Explanation of an Intensified Causes of an Intensified Possible Consequences of an Intensified Human Actions to Reduce Gas Emissions Number of Pre-Instruction Percentage of Number of Post-Instruction Percentage of Wilcoxon T * * * * P Table 3. Change in scientific conceptions for student sample (n = 420). * p <.01. difficulty with the explanation of an intensified greenhouse effect even after instruction. Alternative conceptions - Major themes indicating alternative conceptions are presented in Table 2. These alternative conceptions for each component represented over 80% of student responses for that component. Common responses across the five components were similar in the beginning and at the completion of instruction. Two major patterns emerged. First, students erroneously equated Earth's greenhouse effect with the literal definition of a greenhouse. Based on this misunderstanding, they often identified causes, consequences, and actions in terms of inadequate amounts of oxygen and the need to stop building greenhouses. Second, students erroneously equated the greenhouse effect with the ozone layer. Based on this misunderstanding, they identified causes, consequences, and actions in terms of aerosols and air conditioners causing holes in the ozone layer, which, in turn, cause more cases of skin cancer. did not indicate that chlorofluorocarbons in older aerosols and air conditioners are greenhouse gases; instead, they indicated that these caused deterioration of the ozone layer. Change in ' Conceptions after Intervention The results about the total number of students who gave correct responses and the percentage of these students in the sample for each of the five components are presented in Table 3. demonstrated statistically significant improvements in understanding scientific conceptions for four of the components. However, they failed to demonstrate a significant improvement for the explanation of an intensified greenhouse effect and continued to have the most difficulty even after instruction. Representative writing samples illustrate the quantitative results described above. In the writing samples below, scientific conceptions are indicated in italics within brackets at the end of each response. All the writing samples are presented in verbatim and in their entirety. A relatively small number of students demonstrated improvements in changing their alternative conceptions in the beginning of instruction to scientific conceptions after instruction. In the following example, a student (male, Hispanic, middle SES, ESOL exited, and Spanish home language) did not demonstrate an understanding of scientific conceptions before instruction. After completion of instruction, the student showed 122 Journal of Geoscience Education, v. 55, n. 2, March, 2007, p

7 understanding of scientific conceptions across multiple components. Pre-instruction writing - "Many, but many things harm the world around us cause pollution, but greenhouses are extraordinarily dangerous. It has been proven true that many dangerous animals are attracked to the cheamicals that plants give off, also the smell and sounds we can't hear attrackt caterpillar that give off smoke fumes, so powerful it can make a hole in the atmosphere. Therefore, all of the reasons why greenhouses are evil is because the animals (caterpillars) give off fumes because the plants in greenhouses have an odor that relaxes them, causing a fume that comes out, as the caterpillars get closers, the fumes get stronger, and a hole form in the atmosphere poulluting the planet. The second reason why they are bad is because they give an odor back that makes people faint and die!. Furthermore, destroy all green houses"!!!!! Post-instruction writing - My name is XXX. I'm a respected Scientist that has been studying the effect for quite a while now. The effect for those who don't know is when a layer of gasses surrounding the Earth that absorbs the suns ultra infrared, especially CO2 (carbon dioxide) warming the earth <partially correct definition of the greenhouse effect>, with the increasing pollution and increasing carbon dioxide, global warming might happen <cause of an intensified greenhouse effect>, this will melt the poles and cause a global Flood <consequence of an intensified greenhouse effect>, we must reduce pollution and start using wisely our natural and unnatural resources <action to reduce greenhouse gas emissions>. often expressed scientific conceptions while also maintaining alternative conceptions at the completion of instruction. A prevalent alternative conception involved the confusion between the analogy of the greenhouse effect to a literal greenhouse. In the following example, a student (female, Hispanic, low SES, ESOL exited, and Spanish home language) thought that the greenhouse effect is the same as a greenhouse before instruction (see the first paragraph in the pre-instruction writing). Even after instruction, she held on to this alternative conception (see the fourth and fifth sentences in the post-instruction writing). Pre-instruction writing - I was a scientist one time I went on the radio to tell the people that they are intensified greenhouse is I would tell them don't get out of the house because it is almost around the whole earth so please be careful! Another reason why I would go to the radio is because there is 75% percent atmosphere is increasing in the earth. Also another reason why I would go to the radio because the consequences that the plants will die and trees will too <consequence of an intensified greenhouse effect>. That's my reasons why I was a scientist. Post-instruction writing - Ladies and gentlemens here's annoucement that I'm going to say about Earth. How Earth's climate is warming? The Earth's climate is warming because of the greenhouse effect and how does it effect the Earth's climate changing. There's this house that's called greenhouse effect that has plants all over the house. This house has plants all over to absorb earth's heat. The amount of greenhouse gases in our atmosphere is increasing because of the heat. The possible consequences is damaging the earth by hotter, floods, hurricanes, tornado, and maybe some people could die <consequence of an intensified greenhouse effect>. This is the annoucements about Earth. Another prevalent alternative conception involved the confusion between the greenhouse effect and the ozone layer. In the following example, before instruction, a student (female, White, middle SES, and English home language) equated the ozone layer with global warming leading to sun burn (see the first four sentences in the pre-instruction writing sample). After instruction, she maintained basically the same ideas, although more elaborate. She equated the ozone layer with the greenhouse effect and global warming (see the second and third sentences in the post-instruction writing) leading to skin cancer (see the third sentence from the last). Pre-instruction writing - I am concerned because the harmful sun rays are hitting our ozone layer. Making holes in it, once too many holes are made the sun rays can hit earth and affect us. This is a global warming. If they do get to hit Earth than you couldn't go outside because you would sun burned easily. It is because of all the different chemicals and gases affect our atmosphere that are made by us the humans < cause of an intensified greenhouse effect>. They affect us really really badly. It affects us by having to stay inside and not being able to go outside. Kids wouldn't be able to play games or have physical education. This is how it affects us so we have to try to stop making the chemicals and gases <action to reduce greenhouse gas emissions>. Post-instruction writing - Hello, my name is XXX and I have some very important news for you. Here on Earth we are having a greenhouse effect. This is when the ozone layer is getting many little holes that will eventually turn into big holes when this happends we will be affected because the Earth will catch the sunrays and it will be very hot. Especially in Florida, because it is already hot there and if the people get hotter they will dehydrate and eventually die. For the people up North where it snows it will be a big change, because there will be no more snow it will be very Lee et al. - Conceptions of the and Global Warming 123

8 Gender SES Ethnicity Home Language English Proficiency Subgroup Pre % of Post % of Wilcoxon T P % Gain Male (n=204) * 23 Female (n=201) * 29 Middle (n=171) * 25 Low (n=234) * 26 African-American (n=36) Hispanic (n=248) * 34 White (n=77) * 22 Haitian (n=30) Haitian-creole (n=30) English (n=135) * 24 Spanish (n=197) * 33 English/Spanish (n=35) * 46 ESOL (n=38) * 16 Exited ESOL (n=171) Non-ESOL (n=196) * * 23 Table 4. Differences in scientific conceptions among demographic subgroups (n = 420). * p <.01. hot <consequence of an intensified greenhouse effect>. This will all happen in a few years. As you might have noticed that in some places it is already hotter than it used to be a couple of years. Like some companies that polute the air with their chemicals of the gasses, cars, companies, and fires all polute <cause of an intensified greenhouse effect>. The animals in wildlife will also be affected, they might loose their homes because it might be too hot <consequence of an intensified greenhouse effect>. If people go out side they might get skin cancer. They will use much energy especially air conditioning. So remember save your Earth. Differences among demographic subgroups - The results about the percentage of students giving correct responses for each demographic subgroup across all the five components combined are presented in Table 4. Wilcoxon T test results show statistically significant improvements after instruction with all demographic subgroups, with the exceptions of African-American and Haitian students. Male students showed 23% gain, compared to 29% gain by female students. from middle- and low-ses backgrounds showed comparable gains (25% and 26%, respectively). With regard to ethnicity, Hispanic students showed the most gain (34%) followed by White students (22%), whereas African-American and Haitian students showed no or little gain (0% and 4%, respectively). Similar results were found with regard to home language, in that English/Spanish bilingual students showed the most gain (46%), followed by Spanish-dominant students (33%) and monolingual English-speaking students (24%), and little gain by Haitian Creole-speaking students (4%). With regard to English proficiency, students who exited ESOL programs showed the most gain (31%), followed by students who were not ESOL students (23%) and students who were currently in ESOL programs (16%). CONCLUSIONS AND IMPLICATIONS This study contributes to the existing literature in several ways. First, it was based on a large-scale intervention at several elementary schools in an urban school district, compared to limited intervention efforts on a small scale in previous research (Mason and Santi, 1998; Rye et al., 1997). Second, it examined differences in students' conceptions among demographic subgroups, whereas studies examining student diversity were largely absent in the literature. Third, involvement of U.S. students in this study contributes to the literature largely based on students in European countries. Finally, it used students' writing samples as the data source, whereas most previous studies used questionnaires or interviews. Prior to their participation in the intervention, the 5th grade students in this study had limited understanding of the greenhouse effect and global warming, except for some understanding of the consequences of an intensified greenhouse effect. The instructional intervention was partially effective in developing scientific understanding of the definition of the greenhouse effect, causes and consequences of an intensified greenhouse effect, and actions that they could take to solve this problem. However, students continued to have difficulty differentiating between the greenhouse effect and an intensified greenhouse effect. Two major patterns emerged, which point out shortcomings in our intervention. First, conceptual confusion between an intensified greenhouse effect and ozone layer depletion was widespread even after instruction. Unfortunately, since this study was undertaken after the intervention had been completed, the concept of the ozone layer was not addressed directly. Second, students were often confused by the analogy of the greenhouse effect and a greenhouse in the literal sense. It is possible that students from diverse backgrounds, especially those learning English as a new language or those with limited experience in school science, might face linguistic difficulty with the analogous and literal meanings of the greenhouse effect. It is also possible that the simplicity of 124 Journal of Geoscience Education, v. 55, n. 2, March, 2007, p

9 the experiment, in which students compared the temperature of two containers (one covered with plastic and the other uncovered), confused the students and led them to continue to literally equate the greenhouse effect with a greenhouse. Additionally, it is possible that the writing prompt was not clearly written and that students did not understand an "intensified greenhouse effect." Asking students to differentiate between the greenhouse effect and global warming may actually have been a more effective way of identifying their alternative conceptions. from nonmainstream backgroundsstudents of color, students learning English as a new language, students from immigrant or low-income families-showed significant improvements after instruction. Hispanic, English/Spanish bilingual, and ESOL-exited students showed the highest gains. The exception involved African-American and Haitian students showing little or no gain. Many of these students came from one inner-city school, which was the lowest performing of the five elementary schools in the study. The results suggest the need for more extensive intervention with teachers and students in low performing, inner-city schools through improved science curriculum and teacher professional development efforts. The results also suggest consideration of constraints and challenges facing inner-city schools, including limited resources and funding, high teacher attrition, disproportionate numbers of beginning or inexperienced teachers, and consequences of poor academic performance on accountability measures (Hewson et al., 2001; Knapp and Plecki, 2001). The results suggest that students' alternative conceptions and learning difficulties should be incorporated into curriculum materials and teacher professional development. Had students' alternative conceptions of the greenhouse effect and global warming been addressed directly in our intervention, students from diverse backgrounds might have gained even greater understanding. A comparison group of students who are taught using different approaches would add to our understanding of how complex ideas, such as the greenhouse effect and global warming, are learned. Perhaps focusing on the related but individual concepts within the national and state standards is first necessary to scaffold students toward an understanding of this complex environmental and societal problem that involves many science concepts (see Figure 1). ACKNOWLEDGEMENTS This work is supported by the National Science Foundation, U.S. Department of Education, and National Institute of Health (Grant No. REC ). Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the position, policy, or endorsement of the funding agencies. The authors acknowledge the generous support from Marisa Collett Burke, Cory Buxton, Peggy Cuevas, and Jane Sinagub. 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