Science · 6th Grade · Weather and Climate · Weeks 28-36

Evidence of Climate Change

Students analyze scientific evidence for past and present changes in Earth's climate.

• Common Core State Standards
• MS-ESS3-5

About This Topic

Climate change is not a new phenomenon -- Earth's climate has shifted many times throughout its 4.5-billion-year history due to orbital cycles, volcanic activity, solar variability, and changes in atmospheric composition. What makes current climate change scientifically significant is the rate of change and its correlation with human activity since industrialization. Understanding the evidence for both past and present climate change is central to the MS-ESS3-5 standard.

Several independent lines of evidence point consistently to the same conclusions. Ice cores from Greenland and Antarctica preserve air bubbles containing ancient atmosphere, allowing scientists to reconstruct CO2 levels and temperatures going back 800,000 years. Tree rings record annual growth, with wider rings indicating warmer and wetter growing seasons. Ocean sediment cores, coral records, and pollen preserved in lake beds add further resolution. Instrumental records since the mid-1800s provide precise, direct measurements of temperature, precipitation, and sea level.

Active learning approaches are especially powerful here because students can work directly with real data. Annotating ice core graphs, comparing tree ring samples, and identifying patterns in temperature records builds the same reasoning skills scientists use -- and makes it harder to dismiss the evidence as one person's opinion.

Key Questions

1. Explain what evidence we have that the Earth's climate has changed over time.
2. Analyze how ice cores and tree rings provide data about past climates.
3. Critique common misconceptions about climate change.

Learning Objectives

• Analyze ice core data to identify trends in past atmospheric CO2 concentrations and global temperatures.
• Compare tree ring width patterns to infer historical climate conditions like rainfall and temperature.
• Explain how instrumental records provide direct evidence of recent climate change.
• Critique common misconceptions about the causes and impacts of climate change.
• Synthesize evidence from multiple sources (ice cores, tree rings, instrumental records) to support claims about climate change.

Before You Start

Earth's Systems and Cycles

Why: Students need a foundational understanding of Earth's interconnected systems (atmosphere, hydrosphere, geosphere) to grasp how climate change affects them.

Introduction to Data Analysis

Why: Students must be able to interpret simple graphs and charts to analyze climate data presented in ice core and temperature records.

Key Vocabulary

Climate Proxy	Natural archives, such as ice cores or tree rings, that scientists use to reconstruct past climate conditions before direct measurements were available.
Atmospheric CO2	Carbon dioxide gas present in Earth's atmosphere, a key greenhouse gas that influences global temperatures.
Instrumental Records	Direct measurements of climate variables like temperature, precipitation, and sea level collected using scientific instruments, typically dating back to the mid-1800s.
Greenhouse Gas	A gas in the atmosphere that absorbs and emits radiant energy, trapping heat and warming the planet. Carbon dioxide is a primary example.

Watch Out for These Misconceptions

Common Misconception

Climate has always changed, so current changes are not unusual.

What to Teach Instead

Earth's climate has indeed shifted throughout history, but current warming is occurring at a rate 10 times faster than any previous natural warming coming out of an ice age. The source of the CO2 increase (isotopically distinct fossil carbon) also confirms a human rather than natural origin.

Common Misconception

Scientists disagree about whether climate change is happening.

What to Teach Instead

Multiple independent studies show that over 97 percent of actively publishing climate scientists agree that current climate change is real and primarily human-caused. Disagreement in public discourse should not be confused with scientific uncertainty, which primarily concerns regional impacts and exact magnitudes, not the basic reality of warming.

Common Misconception

Ice cores and tree rings are unreliable because they are indirect measurements.

What to Teach Instead

Proxy records like ice cores and tree rings have been validated extensively against direct instrumental records where they overlap. Multiple independent proxies from different parts of the world show the same patterns, giving scientists high confidence in reconstructed climate records going back hundreds of thousands of years.

Active Learning Ideas

Data Analysis: Ice Core CO2 and Temperature Records

Provide students with simplified graphs of CO2 concentration and temperature deviation reconstructed from Antarctic ice cores over the past 400,000 years. Students annotate cycles, identify the correlation between CO2 and temperature, and write a claim-evidence-reasoning paragraph explaining what the data shows.

35 min·Pairs

Gallery Walk: Multiple Lines of Evidence

Set up six stations around the room, each displaying a different type of climate evidence (ice cores, tree rings, sea level records, Arctic sea ice extent, species range shifts, glacial retreat photographs). Groups rotate with a recording sheet, summarizing what each source shows and rating how far back in time it can record.

40 min·Small Groups

Socratic Seminar: Addressing Climate Change Misconceptions

Distribute a list of five common public misconceptions about climate change. Students research one in pairs, then the class convenes for a structured discussion where they present the scientific evidence that addresses each misconception. The teacher facilitates but does not lecture, drawing out student reasoning.

50 min·Whole Class

Real-World Connections

• Paleoclimatologists analyze ice cores drilled in Antarctica and Greenland to understand long-term climate cycles, informing current climate models used by organizations like NASA and NOAA.
• Forensic scientists sometimes use tree ring analysis, called dendrochronology, to help date historical artifacts or determine environmental conditions at the time of a past event.
• Meteorologists and climate scientists use decades of instrumental records from weather stations worldwide to track changes in average global temperatures and predict future climate scenarios.

Assessment Ideas

Quick Check

Provide students with a simplified graph showing CO2 levels from an ice core record and a separate graph of global temperature from instrumental records. Ask them to write two sentences describing the relationship they observe between CO2 levels and temperature.

Discussion Prompt

Pose the question: 'Imagine you are explaining to a younger sibling why scientists are concerned about climate change. What are two pieces of evidence you would share, and why are they convincing?' Facilitate a brief class discussion where students share their chosen evidence.

Exit Ticket

On an index card, have students write down one method scientists use to study past climates (e.g., ice cores, tree rings) and one piece of evidence that shows the climate is changing *now* (e.g., rising temperatures, sea level rise).

Frequently Asked Questions

What evidence do scientists have that Earth's climate has changed?

Scientists use multiple independent lines of evidence: ice cores (trapped air bubbles preserve ancient CO2 levels and temperature signals), tree rings (annual growth reflects temperature and moisture), ocean sediment cores, coral skeletons, glacier retreat photographs, rising sea level records, and direct thermometer readings going back to the 1800s. All point to consistent warming over the industrial era.

How do ice cores tell us about past climates?

As snow accumulates in places like Greenland and Antarctica, it traps tiny air bubbles. Scientists drill ice cores and analyze those bubbles to measure ancient CO2, methane, and other gases. Ratios of oxygen isotopes in the ice itself reflect past temperatures. Ice cores have provided climate records spanning 800,000 years and multiple glacial cycles.

What do tree rings tell us about historical climate?

Trees produce one ring per year, with wider rings indicating warmer, wetter growing seasons and narrower rings indicating cooler or drier years. By overlapping ring patterns from living trees and ancient wood preserved in buildings or bogs, dendrochronologists have built continuous records spanning thousands of years and covering large geographic areas.

How does analyzing climate evidence connect to active learning?

Working with real data sets -- annotating ice core graphs, comparing tree ring widths, or mapping glacier retreat -- puts students in the role of scientist rather than passive reader. They practice the same skills researchers use: identifying patterns, evaluating evidence quality, and constructing arguments. This builds both content understanding and scientific reasoning that transfers to other topics.