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. Students' 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 rnaxe 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' 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.
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 Earths 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 Cnange, 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. …