Essential Lens: Analyzing Photographs Across the Curriculum

Classroom Resources > Essential Lens: Analyzing Photographs Across the Curriculum > 9. Earth, Climate, and Change: Observing Human Impact

Education English Language Arts Mathematics Science Social Studies & History

6-8, 9-12, College/Adult

Earth, Climate, and Change: Observing Human Impact

Introduction

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Climate change means the unusually rapid warming of the atmosphere and its scientifically documented effects around the world. The warming is measurable: although annual local weather patterns vary, the average global temperature has increased by nearly 0.8ºC (1.5º F) in the last 100 years. This might not sound like much, but even small temperature changes occurring worldwide have a noticeable effect on the climate, which affects habitats for all organisms, including humans. In addition, the pace of change is increasing: most of the rise in average global temperature has occurred in the last few decades.

Climate change and the human contribution to this change is sometimes denied or depicted as an uncertainty. However, according to the American Association for the Advancement of Science (see References and Further Reading), climate change is not controversial: 97 percent of climate scientists are certain that human-caused climate change is occurring. Climate research is continuing, with scientists and engineers working to predict the consequences of climate change and finding ways to overcome its negative impact.

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People around the world, in cities and in rural areas, are experiencing more extreme temperatures, stronger storms, and loss of land from rising sea levels. Some of the most dramatic effects of climate change are related to water: either too much water that results in flooding or too little that results in droughts and wildfires.

For example, even slightly increased temperatures that result from climate change will melt sea ice. Both melting sea ice and higher temperatures increase the volume of the ocean. Greater ocean volume means higher levels of water along coastal areas, which adds to erosion of these areas. In addition, melting sea ice can lead to global changes in water circulation: water from the melted ice forms a layer at the sea surface that is less dense than the underlying water because it is less salty, potentially preventing the patterns of deep ocean currents from rising to the surface. Melting sea ice also speeds up the warming of the Arctic because water absorbs 80 percent of sunlight, which is about the amount of sunlight that a cover of sea ice reflects.

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In this collection, students will use photographs as data to observe and identify changes over time in water-related features such as coastlines or glaciers. They will use photographs to prompt discussions on the consequences of climate change to humans and habitats. They might even use photographs as motivation to explore how they can be citizen scientists and engineers in studying climate change and mitigating its negative effects in their own communities.

Note: The term “weather” refers to short-term atmospheric features such as precipitation, wind, and temperature. “Climate” means the long-term weather patterns of an area; for example, average temperatures over many years.

Older references might use the term “global warming” to refer to climate change. Global warming refers to the heating effect of greenhouse gases accumulating in the atmosphere. Scientists study more than just how temperature is affected by human activity, however. To emphasize that human activity does more than just influence temperature, the more common term for rising average global temperatures and its effect is “climate change.”

Curriculum Snapshot

Using photographs and satellite imagery to identify and observe changes in the Earth’s features over time that indicate climate change
Using photographs and satellite imagery to prompt discussions on the relationship between the water cycle, weather, and climate, especially the contribution of oceans

Key Learning Targets

Students will:

Observe how living organisms alter Earth’s processes and structures over time.
Consider how human activity changes the atmosphere, hydrosphere, and biosphere over time.
Discuss the interactions between processes on the Earth’s surface and human activities.

Essential Questions

These big ideas or essential questions organize the content and topics.

What evidence have scientists found about the impact of climate change?
How do the movements of water affect the Earth and its systems?

Prerequisite Knowledge

Before doing these activities, especially the third activity (Where Does the Water Go? A Global Journey), students should be familiar with the water cycle.

Activating Students’ Prior Knowledge
Middle & High School
Earth and Space Science, Environmental Studies, Physical Science, Social Studies

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In pairs or small groups, give students one or more of the photographs. Ask students to first talk about their overall impressions of the image, what they see, and what they think the image is of and/or trying to portray. Then have the groups write their observations about evidence they see of effects on habitats, signs of human activity, or the impact of humans.

(Students might or might not see any or all of these features in their photographs. For example, although they can’t see the dam in 3506, they can figure out where it is, hypothesize that the dramatic change in the water is the result of human activity, and brainstorm about its effects on habitats. Although they can’t see how climate change increases coastal erosion, they can begin to hypothesize about its impact on habitats, including for humans.)

In groups or as a class, discuss how any activity or impacts they see might be affecting or have affected communities of organisms, including humans. Emphasize that at this point, no questions or ideas are considered right or wrong.

Note: Frequently asked questions by students about sea level are: What causes sea levels to rise? What is the impact? Changes in sea level can be caused by several factors:

Exchange of water stored on land in glaciers and ice sheets with ocean water
Water expansion as the ocean warms
Storm surges affected by alterations in surface and deep ocean circulation
Changes in terrestrial water storage, such as extraction of groundwater, building of reservoirs, and runoff
Subsidence (caving or sinking of land) in river delta regions, land movements, and tectonic displacements

Impacts of rising sea level include shoreline erosion, effects on wetlands and coral reefs, and loss of habitats and land near coasts or rising rivers and streams.

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Note: Students might ask about permafrost. Permafrost is soil that is permanently frozen. When the permafrost melts, the soil is more susceptible to erosion. (In addition, permafrost stores carbon. When the ice melts, the stored carbon is released as greenhouse gases such as carbon dioxide, which further contributes to climate change.)

The term hurricane is used for high wind, cyclonic storms in the Atlantic and Northeast Pacific. The same storm is a typhoon in the Northwest (Asian) Pacific, and a cyclone in the South Pacific and Indian Ocean. Monsoon is the term for a seasonal wind in Southeast Asia. Some monsoons bring heavy rain.

Also, see the Habitable Planet resources, which have potential discussion topics and common student misconceptions, such as the possibility of a technological fix or the impossibility of human extinction.

What Is the Evidence?
Middle & High School
Earth and Space Science, Environmental Studies, Physical Science, Social Studies

Background

Weather changes and overall climate can vary between warm and cool periods; however, average global temperatures have unquestionably risen in the last 100 years. Photographs can record how the effects of small changes in temperature will, over time, result in dramatic changes in oceans, coastlines, and other habitats. Photographs are essential for recording these changes because they might occur slowly, with variation over months or years that obscures a definite overall trend. For example, because coral reefs grow slowly, changes to their structure or composition are difficult to observe day to day. The same slow alterations occur to polar caps, glaciers, and sea level. Over time, however, these small changes add up to a noticeable difference. In this activity, students will use photos taken of a single location at different times to look for evidence of climate change.

LEARNING TARGETS

I can use photographs to observe changes over time and make inferences on the effects of these changes.
I can ask questions about the evidence of change that is altering the global climate.

#3518 Drought Conditions in California

Climate scientists have overwhelming evidence that human activities are affecting our climate, mainly through increased production of greenhouse gases such as methane and carbon dioxide (CH₄ and CO₂). Many sources generate these gases, including normal metabolism. Humans exhale CO₂, and several types of bacteria generate CH₄. Burning fossil fuels also generates greenhouse gases, however, and our use of petroleum-based fuels and the amount of greenhouse gases in the atmosphere have increased dramatically since the nineteenth century. Greenhouse gases re-radiate heat, raising atmospheric temperatures. Higher temperatures increase the amount of water that evaporates from oceans into the air. This affects land conditions as precipitation patterns change, potentially leading to floods or droughts.

Although we sometimes think of climate change as affecting only summer temperatures, in many ecosystems, warming winters also severely affect plants, animals, and humans. For example, increased atmospheric moisture makes snowstorms more severe. A lack of freezing days can cause infestations of insects that would normally be killed by freezing temperatures.

Another consequence of climate change is rising sea levels because of several factors, including higher water temperatures, and increased volume as water that is trapped as ice sheets and glaciers melts. When sea levels are higher, islands and coastal regions are more seriously affected by storm surges and, on an everyday basis, by encroaching salt water that changes habitats. Plants, animals, and microorganisms that are adapted to particular environmental conditions must adapt or change habitats to survive. Changing habitats affect conditions for humans, such as our supply of food and water.

Begin the Activity

Materials:

Paper
Pencils or pens

In pairs or small groups, give students a series of photographs of the same location taken at different times. Have students observe, and then list and describe all the features in each photograph. Have them pay particular attention to anything that changed or anything that is exactly the same in the photos.

#3503 Muir Glacier and Muir Inlet, 1980

#3504 Muir Glacier and Muir Inlet, 2003

Once they have generated a list, have the students mark the list for items that changed and items that did not change in the photo series. Have the students use the list to draw a Venn diagram. One circle will list items in the earlier photo, with their descriptions, that look different from items in the later photo. The other circle will list items in the later photo, with descriptions, that look different from the earlier photo. The intersection will list items that appear the same in both photos. (So the nonintersecting parts might list the same items—such as a mountain or a rock—but will have different descriptions for those items, such as snow-covered or bare. The intersecting part will have items that have the same descriptions for both photos, such as a rocky ridge with a little snow.)

Optional, advanced, or group discussion example: Photo 3516 show photos before and after Hurricane Sandy, a particularly strong hurricane in 2012. Although an individual hurricane might seem like an isolated event, increased atmospheric moisture can make storms more severe.

When all the teams are finished, have them share their results with the class. Ask guiding questions and bring up discussion questions about key points in each set.

Questions to Consider

What might be the impact of these changes beyond what is in the photo?
What changes might be disruptive for wildlife habitats, vegetation, or human communities?
What ways can you think of to reduce the disruptive effects of the changes you observed?
- Suggested activity for this question: Have students make a two-column table with pros and cons of trying to reduce a disruptive effect of climate change. For example, if students think of building a dam to prevent floods, a good exercise might be writing down the upstream effects of a dam.
Optional question if your class has covered material on Earth’s Systems (ES22): What might be the scientific basis for any changes your team noted in the earlier and later photographs?

Students’ answers will vary depending on the set of photos they received. Their answers should reflect the changes they have already noticed and what will happen if those changes continue.

For example, if they noticed that the amount of water in an area has increased over time, they might say that the area is likely to continue flooding, and people who live in the area will have to move.

They might note that coral reef death affects species that depend on coral habitats. (Coral bleaching, which is loss of the algae that live in coral tissues, occurs when water is too warm and can lead to death of the coral.)

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They might note that flooding could continue if warmer temperatures result in increased water evaporation, leading to the heavy rainfall that causes flooding. In contrast, increased evaporation in places that are normally dry results in droughts. Other impacts include heat waves; warmer winters; changing ecosystems; a possible loss, decrease, or increase in species; and effects on agriculture from drought, heat, and floods.

Anything that causes changes in the ecosystem is likely to be disruptive to wildlife. For example, flooding will disrupt a habitat for any wildlife living in the flooded area. Students might note that, although humans often have the technology to help them live in changing conditions, severe changes, such as extreme flooding or drought, might cause people to move from a community.