Analyze data linking greenhouse gases to temperature change

How Did Scientists First Connect CO₂ to Temperature?

Have you ever sat in a car on a sunny day with the windows up? The inside of the car gets much hotter than the air outside. Scientists noticed that Earth's atmosphere works in a similar way. Certain gases trap heat and warm our planet. This idea is not new — researchers have studied it for over 150 years.

Our anchoring phenomenon is this: Earth's average temperature has risen about 1.1 °C since the late 1800s, and during that same time, carbon dioxide (CO₂) in the atmosphere has jumped from about 280 parts per million (ppm) to over 420 ppm. Is that just a coincidence, or do the data tell us something important? Let's trace the history of this discovery.

Over more than a century, scientists have gathered evidence connecting greenhouse gas concentrations to rising temperatures. The big question is: how do we read and interpret this data ourselves? That is exactly what we will learn in this lesson.

Core Principles: The Greenhouse Effect and Key Gases

Before we analyze data, we need to understand the science behind it. Earth's atmosphere contains greenhouse gases (gases that trap heat energy from the sun). Without them, Earth's average temperature would be about −18 °C — way too cold for life! The natural greenhouse effect keeps our planet warm enough. The problem starts when human activities add extra greenhouse gases to the atmosphere.

Visualizing the Greenhouse Effect

The diagram below shows how the greenhouse effect works step by step. Follow the numbered arrows to trace the path of energy from the sun to Earth's surface and back into the atmosphere.

Notice the cause and effect relationship shown in the diagram. More greenhouse gas molecules means more heat gets trapped in step ③. This is a crosscutting concept in science: a change in one part of a system causes a change in another part. When you analyze data, you are looking for exactly this kind of pattern.

How Scientists Measure and Link the Data

Scientists use two main data sets to study climate change. The first is the concentration of greenhouse gases (measured in ppm). The second is the global average temperature anomaly (measured in °C above or below a baseline). When both data sets are plotted on the same timeline, a clear pattern appears.

Where Does the Data Come From?

Modern CO₂ data comes from instruments at observatories like Mauna Loa. For past data (going back hundreds of thousands of years), scientists drill ice cores (long tubes of ancient ice from glaciers). Tiny air bubbles trapped in the ice hold samples of the atmosphere from long ago. Scientists can measure the CO₂ inside those bubbles.

Temperature data comes from weather stations, ocean buoys, and satellites around the world. For past temperatures, scientists use proxy data (indirect clues like tree rings, coral growth patterns, and the chemistry of ice cores). All of these sources are combined into a global average.

Simple Math: Calculating a Temperature Anomaly

Reading Real Data: CO₂ and Temperature Over Time

Now let's look at actual data. The table below shows CO₂ concentration and global temperature anomaly for selected years. The anomaly baseline is the average temperature from 1951 to 1980.

Look at the pattern in the graph above. From 1880 to about 1960, CO₂ rose slowly, and temperature changed only a little. After 1960, both CO₂ and temperature rose much faster. The steepest climb happens from 2000 to 2020. This matches the time period when humans burned the most fossil fuels. The crosscutting concept of Stability and Change helps us see that Earth's climate was relatively stable for thousands of years but is now changing rapidly because of human activities.

Worked Example: Analyzing the Data

Let's practice the science and engineering practice of analyzing and interpreting data. We will use the table from Section 5 to answer a question.

Strengths and Limitations of Climate Data

Not all data is created equal. Scientists think carefully about the strengths and limitations of each type of evidence. Understanding this helps you evaluate claims about climate change like a real scientist.

Looking Ahead: Other Greenhouse Gases and Future Projections

CO₂ is the most talked-about greenhouse gas, but it is not the only one. Other gases trap heat too, and some are much more powerful per molecule. In high school and beyond, you will learn about climate models (computer simulations that predict future temperatures). For now, let's see how the main greenhouse gases compare.

Even though methane and nitrous oxide are more powerful per molecule, CO₂ is responsible for the most total warming because we release so much of it. This is an example of the crosscutting concept of Scale, Proportion, and Quantity — both the strength of a gas and the amount matter.

In more advanced courses, you will use computer models to project future temperatures under different scenarios. Some scenarios assume humans reduce emissions quickly; others assume emissions keep growing. The data skills you are learning now — reading graphs, calculating changes, identifying patterns — are the same skills climate scientists use every day.

Practice Problems

Test your understanding with these five problems. They get harder as you go. Use the data table from Section 5 if you need it.

Lesson Summary