20

The earth has a variety of climatic pat-terns, which consist of different conditionsof temperature, precipitation, humidity,wind, air pressure, and other atmosphericphenomena. These result from a varietyof factors. Climate and changes in climatehave influenced in the past and will continue to influence what kinds of lifeforms are able to exist. Understandingthe basic principles that contribute tomaintaining and causing changes inweather and climate increases our abilityto forecast and moderate the effects ofweather and to make informed decisionsabout human activities that may contributeto climate change.

The map is organized around fourstrands—temperature and winds, watercycle, atmosphere, and climate change.The progression of understanding beginsin the elementary grades with observationsabout heat transfer, changes in waterfrom one state to another, and changes in weather over the course of a day andover the course of seasons. By middleschool, the focus is on the water cycle,patterns of change in temperature, andthe notion of climate change. In highschool, seasons and winds and the watercycle are related to gravity and the earth’srotation, and climate change is related tonatural causes and human activities.

Benchmarks in this map about temper-ature and winds draw on ideas about heattransfer and transformation in the ENERGY

TRANSFORMATIONS map. Benchmarks inthe climate change strand are also relatedto the SCIENCE AND SOCIETY map. Thewidespread use of climate models toimprove our understanding of the earth’sclimate system and climate change sug-gests a connection to benchmarks in theMODELS map as well.

NOTES

The left-hand side of the temperature andwinds strand presents a progression ofunderstanding of seasons. The explanation ofthe seasons in terms of the tilt of the earthrequires students to engage in fairly complexspatial reasoning. For this reason, althoughthe idea is introduced at the 6-8 grade levelin Benchmarks, the map places it (4B/H3) at the 9-12 level.

Benchmarks related to the heating of materi-als and the transfer of thermal energy lay theconceptual groundwork for understandingsolar heating, global circulation, seasonalweather patterns and climate, and the effectof greenhouse gases. To understand howthermal energy moves in both oceanic andatmospheric systems, students need to knowthat convective currents are an essentialmechanism that aids in that movement. Inmiddle school, understanding of convectioncurrents is linked to experiences with rele-vant phenomena. Understanding convectionin terms of gravity, buoyant forces, and pres-sure is not expected until high school. It isnot necessary for students to have a molecu-lar comprehension of thermal energy to beable to understand atmospheric and oceaniccirculation patterns and their role in climate.

Several lines of conceptual development con-verge in the new 9-12 benchmark that begins“Climatic conditions result from….” Theseinclude an understanding of temperature pat-terns over the earth, atmospheric andoceanic circulation patterns, and the watercycle. A double-headed arrow between thisbenchmark and another new benchmark(4B/H6) on climate change indicates thatthey are closely related but that neither isconceptually dependent on the other.

R E S E A R C H I N B E N C H M A R K S

Students of all ages (including college students and adults)have difficulty understanding what causes the seasons.Students may not be able to understand explanations of theseasons before they reasonably understand the relative size,motion, and distance of the sun and the earth (Sadler, 1987;Vosniadou, 1991). Many students before and after instructionin earth science think that winter is colder than summerbecause the earth is farther from the sun in winter (Atwood& Atwood, 1996; Dove, 1998; Philips, 1991; Sadler, 1998).This idea is often related to the belief that the earth orbitsthe sun in an elongated elliptical path (Galili & Lavrik, 1998;Sadler, 1998). Other students, especially after instruction,think that the distance between the northern hemisphereand the sun changes because the earth leans toward the sunin the summer and away from the sun in winter (Galili & Lavrik,1998; Sadler, 1998). Students’ ideas about how light travelsand about the earth-sun relationship, including the shape ofthe earth’s orbit, the period of the earth’s revolution aroundthe sun, and the period of the earth’s rotation around its axis,may interfere with students’ understanding of the seasons(Galili & Lavrik, 1998; Salierno, Edelson, & Sherin, 2005). Forexample, some students believe that the side of the sun notfacing the earth experiences winter, indicating a confusionbetween the daily rotation of the earth and its yearly revolutionaround the sun (Salierno, Edelson, & Sherin, 2005).

Although upper elementary students may identify air asexisting even in static situations and recognize that it takesspace, recognizing that air has weight may be challengingeven for high-school students (Sere, 1985; Driver et al.,1994a; Krnel, Watson, & Glazar, 1998). Students of all ages(including college students) may believe that air exerts forceor pressure only when it is moving and only downwards(Driver et al., 1994a; Sere, 1985; Henriques, 2002; Nelson,Aron, & Francek, 1992). Only a few middle-school studentsuse the idea of pressure differences between regions of theatmosphere to account for wind; instead, they may accountfor winds in terms of visible moving objects or the movementof the earth (Driver et al., 1994a).

Before students understand that water is converted to aninvisible form, they may initially believe that when waterevaporates it ceases to exist, or that it changes location butremains a liquid, or that it is transformed into some otherperceptible form (fog, steam, droplets, etc.) (Bar, 1989;Russell, Harlen, & Watt, 1989; Russell & Watt, 1990; Krnel,Watson, & Glazar, 1998). With special instruction, somestudents in 5th grade may be able to identify the air as thefinal location of evaporating water (Russell & Watt, 1990),but they must first accept air as a permanent substance (Bar,1989). For many students, difficulty understanding theexistence of water vapor in the atmosphere persists in middleschool years (Lee et al., 1993; Johnson, 1998). Students canunderstand rainfall in terms of gravity once they attributeweight to little drops of water (typically in upper elementarygrades), but the mechanism through which condensationoccurs may not be understood until high school (Bar, 1989).

Students of all ages may confuse the ozone layer with thegreenhouse effect, and may have a tendency to imagine thatall environmentally friendly actions help to solve all environ-mental problems (for example, that the use of unleaded petrolreduces the risk of global warming) (Andersson & Wallin, 2000;Koulaidis & Christidou, 1998; Meadows & Wiesenmayer, 1999;Rye, Rubba, & Wiesenmayer, 1997). Students have difficultylinking relevant elements of knowledge when explaining thegreenhouse effect and may confuse the natural greenhouseeffect with the enhancement of that effect (Andersson &Wallin, 2000).

See ENERGY RESOURCES and ENERGY TRANSFORMATIONS

for additional research.

THE PHYSICAL SETTING

WEATHER AND CLIMATE (4B)

21

WEATHER AND CLIMATE 4T H E P H Y S I C A L S E T T I N G