This ThinkTV segment demonstrates the complex relationships between the land and Earth's climate system. It emphasizes five land factors that influence climate: latitude, elevation, topography, surface reflectivity, and land use.
When first thinking about land masses and climate, it makes sense to remember the wisdom of real estate agents: think location, location, location! The effects of land on the atmosphere and its energy balance depend on the location of the land mass on the globe, especially its latitude—how far north or south it is from the equator. At the equator, the Sun’s rays strike the surface of Earth at right angles (90°) and the energy is concentrated. Land at higher latitudes receives less concentrated solar radiation due to the smaller angle at which the Sun’s rays arrive at the surface. This makes their climates generally cooler than land near the equator.
Whether a land mass is located in the Northern Hemisphere or the Southern Hemisphere also affects its climate. The Southern Hemisphere has more ocean area than the North, and ocean water stores large quantities of heat. As a result, climate conditions over land in the Southern Hemisphere may be more moderate than similar latitudes in the Northern Hemisphere.
An increase in the elevation, or altitude, of a land mass also makes for a cooler climate. Increases in altitude mean thinner air, which makes the atmosphere less able to absorb and retain heat. There are other important climate factors besides location. Surface properties of land masses play a role in how land and climate influence each other. Properties such as surface reflectivity, or albedo, roughness, water-holding capacity, and plant life all affect surface temperatures across a land mass. Surfaces with high albedo, often caused by snow or ice, reflect more sunlight energy than dark surfaces—a cooling influence on climate. The removal of forests, deforestation, increases soil temperatures by exposing soils to sunlight which increases their release of carbon dioxide—a greenhouse gas and a warming influence on climate.
Changes to the land surface also affect how water moves, and whether it evaporates from the soil surface, drains through the soil, or is absorbed by the roots of plants. This is called surface water balance, and affects local humidity. This affects local climate, since moist air retains heat longer than dry air.
Changes to the carbon cycle or the nitrogen cycle caused by human activities such as burning forests or using nitrogen fertilizers also affect climate conditions.
As scientists increase their ability to monitor land masses, especially by using data from satellites, they will improve their understanding of the role that land plays in Earth's climate system.
Here are suggested ways to engage students with this video and with activities related to this topic.
Viewing the video:
Before: Location matters when it comes to a land mass and its local climate. Why does location on Earth make so much difference? Name three cities whose different locations give them different climates.
During: See if you can spot some natural ways and some human-caused ways in which land affects local climate conditions.
After: How many effects of land masses on local climate conditions can you name?
Taking a stand: Have students take a side (or assign them to a side) on the following issue: In order to reduce their impact on global climate conditions, farmers in Brazil should be required to reduce the burning of rainforest to clear land. Ask students to research information on their chosen side, then come to class prepared to support their argument in a debate or submit it as a writing assignment.
Connecting to subject areas—math: Have students determine the percentage of land versus ocean in the Northern Hemisphere and in the Southern Hemisphere. Water stores more heat energy than land, and releases it more slowly. [Water has a higher specific heat than land.] Does the difference in this ratio support the statement that the Southern Hemisphere has a more moderate climate than locations in the Northern Hemisphere at the same latitude?
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www.pbsstudents.org and enter the Assignment Code, or click on the Assignment URL to share the assignment as a link.