Science · 7th Grade · Earth's Changing Surface · Weeks 28-36

Global Climate Change: Evidence and Impacts

Students evaluate evidence for historical and modern shifts in Earth's climate.

• Common Core State Standards
• MS-ESS3-5

About This Topic

Climate change refers to long-term shifts in global temperature and precipitation patterns, distinct from day-to-day weather variability. MS-ESS3-5 asks students to ask questions to clarify evidence for the factors that have caused the rise in global temperatures over the past century. Students evaluate multiple independent lines of evidence: ice core records showing atmospheric composition going back 800,000 years, sediment cores recording past sea level and temperature, coral growth records, tree rings, and continuous direct atmospheric measurements since 1958.

The physical mechanism is the enhanced greenhouse effect. Human activities, primarily fossil fuel combustion and deforestation, have raised atmospheric CO2 from roughly 280 ppm before industrialization to over 420 ppm today, a level not recorded in at least 800,000 years of ice core data. This additional CO2 absorbs more outgoing infrared radiation, warming the lower atmosphere. Observable consequences include rising global average temperatures, shifting precipitation patterns, accelerating glacier retreat, rising sea levels, ocean warming and acidification, and measurable shifts in species distributions and seasonal timing.

This topic benefits from structured investigation rather than lecture. When students analyze actual temperature anomaly data or ice core records and form their own conclusions, they engage with the evidence directly rather than accepting a secondhand summary.

Key Questions

1. How do scientists determine what the climate was like millions of years ago?
2. What is the relationship between carbon dioxide levels and global temperature?
3. How might a changing climate affect biodiversity in different biomes?

Learning Objectives

• Analyze ice core data to identify trends in atmospheric carbon dioxide concentration over the past 800,000 years.
• Evaluate the relationship between historical carbon dioxide levels and global average temperatures using graphical representations.
• Explain the mechanism of the enhanced greenhouse effect, citing human activities as a primary cause.
• Compare projected impacts of climate change on biodiversity in two different biomes, such as coral reefs and arctic tundra.
• Critique the reliability of different types of climate evidence, such as tree rings versus direct atmospheric measurements.

Before You Start

Earth's Systems and Their Interactions

Why: Students need a foundational understanding of Earth's atmosphere, hydrosphere, and biosphere to comprehend how changes in one system affect others.

Weather vs. Climate

Why: A clear distinction between short-term weather patterns and long-term climate trends is essential for understanding the concept of climate change.

Key Vocabulary

Greenhouse Effect	The natural process where certain gases in Earth's atmosphere trap heat, warming the planet. This process is enhanced by increased concentrations of these gases.
Carbon Dioxide (CO2)	A major greenhouse gas released through burning fossil fuels and deforestation. Its concentration in the atmosphere is a key indicator of climate change.
Temperature Anomaly	The difference between a recorded temperature and the long-term average temperature for a specific location and time period.
Ice Core	A long cylinder of ice drilled from glaciers or ice sheets, containing trapped air bubbles and layers that provide data on past atmospheric composition and climate.
Biome	A large geographical area characterized by specific climate conditions and distinct plant and animal communities, such as deserts, forests, or grasslands.

Watch Out for These Misconceptions

Common Misconception

Climate and weather are the same thing.

What to Teach Instead

Weather is the day-to-day atmospheric conditions at a specific location. Climate is the long-term average pattern of those conditions over decades. A cold week in summer does not contradict a long-term warming trend any more than one slow car on a highway contradicts an average speed increase. Establishing this distinction clearly is foundational before engaging with any climate data.

Common Misconception

Scientists' climate projections are speculative guesses.

What to Teach Instead

Climate projections are outputs of physically-based models that encode known laws of energy absorption, fluid dynamics, and atmospheric chemistry. Model projections published in the 1990s have been validated by actual observed temperatures in the decades since, with warming tracking within the projected range. Examining a graph of early projections alongside actual temperature measurements makes this empirical validation visible to students.

Active Learning Ideas

Inquiry Circle: Reading Ice Core Data

Groups receive a simplified dataset of CO2 concentration and temperature anomaly from the EPICA ice core record available from NOAA. Students plot CO2 and temperature on the same time axis, analyze the relationship, and mark the current CO2 level on their graph. Each group writes a claim, supported by the data, about whether current CO2 levels fall within or outside the range of historical natural variation.

50 min·Small Groups

Think-Pair-Share: How Do Scientists Know Past Temperatures?

Students individually list as many proxy climate indicators as they can think of without teacher help, then combine lists with a partner and reason about what physical or chemical property each indicator preserves over time. The class compiles a full list and discusses why multiple independent proxy records that agree are more convincing than relying on a single data source.

20 min·Pairs

Stations Rotation: Climate Evidence Stations

Six stations each present one category of evidence: direct temperature records from 1880 to present, satellite data showing Arctic sea ice extent decline, glacier before-and-after photographs from Glacier National Park, sea level tide gauge and satellite records, ocean heat content data, and phenology records showing earlier average spring bloom dates in the US. Students assess consistency across evidence types using a tracking sheet.

50 min·Small Groups

Gallery Walk: Biome Impacts

Post maps and brief summaries showing projected shifts in five biomes (Arctic tundra, temperate forests, coral reef systems, tropical rainforest, and grasslands). Student groups annotate each with the specific climate variable driving the projected change and the resulting impact on biodiversity. The class identifies which biomes face the most severe projected disruption and the reasoning behind those conclusions.

35 min·Whole Class

Real-World Connections

• Paleoclimatologists, like those at the National Center for Atmospheric Research, study ice cores from Greenland and Antarctica to reconstruct past climates, providing crucial data for understanding current climate trends.
• Ecologists working for organizations such as The Nature Conservancy monitor species distribution in regions like the Amazon rainforest and the Great Barrier Reef to assess how changing temperatures and precipitation patterns are affecting biodiversity.

Assessment Ideas

Quick Check

Provide students with a graph showing CO2 levels and global temperature over the last century. Ask them to write two sentences describing the observed relationship and one question they still have about the data.

Discussion Prompt

Pose the question: 'Imagine you are a scientist presenting evidence for climate change to a community group. Which two types of evidence (e.g., ice cores, sea level rise, tree rings) would you prioritize and why? How would you explain them clearly?'

Exit Ticket

On an index card, have students define 'enhanced greenhouse effect' in their own words and list one human activity that contributes to it. They should also name one observable consequence of this effect.

Frequently Asked Questions

How do scientists determine what the climate was like millions of years ago?

Scientists use proxy records, indirect measurements that preserve a signature of past climate. Air bubbles trapped in glacial ice contain ancient atmosphere, allowing direct measurement of past CO2 levels. Oxygen isotope ratios in ice, coral, and sediment cores record past ocean temperatures. Tree rings record annual growth influenced by temperature and moisture. When independent methods agree on the same reconstruction, confidence in the result is high.

What is the relationship between carbon dioxide levels and global temperature?

The data show a strong positive relationship: periods of high CO2 in Earth's history correspond to warmer global temperatures, and low CO2 periods correspond to cooler conditions. CO2 absorbs outgoing infrared radiation and re-emits some of it toward Earth's surface, reducing the rate at which the planet cools. Current CO2 levels above 420 ppm are higher than any point in the 800,000-year ice core record.

How might a changing climate affect biodiversity in different biomes?

Climate change is shifting geographic ranges, altering the timing of seasonal events, and increasing the frequency of extreme conditions that many species cannot tolerate. Arctic species face habitat loss as sea ice and permafrost decline. Coral reefs are damaged by warming and acidification. Some temperate species are expanding ranges northward while others face reduced suitable habitat. The rate of change is faster than many populations can adapt to through natural selection.

How does active learning help students evaluate climate change evidence?

Climate change evidence is frequently misrepresented in public discourse. When students analyze actual ice core datasets, plot temperature records themselves, and examine satellite imagery of glacier retreat, they become familiar with the evidence firsthand rather than being told what it shows. Students who have worked with the data are significantly better equipped to identify when someone is cherry-picking a short time window or a single data source.