Understanding Climate Change | 1.1

Let's do a quick activity to get this lesson started. You'll think about what climate change means to you and what you already know about the topic before learning more.

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Climate change is...

How would you finish that sentence? Take a few minutes and jot down as many sentences as you can.

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Now, read over your sentences. Do you feel confident about all of them? Circle the ones you feel the strongest about. Then, write a couple of sentences explaining why you feel that way.

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What did you write? Share with a friend or classmate, or you can [[☃ explanation 1]]

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In this activity, you'll come up with a working definition of climate change.

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##Defining Climate Change

It's important to have a common understanding of what we mean when we talk about climate change. Let's look at some definitions of climate change and consider their strengths and weaknesses.

In this course, we will adopt a scientific and functional definition of climate change:

Climate change refers to changes in the measures of Earth’s climate over a long period of time including weather, precipitation, and temperature patterns.

Does this explanation reflect your understanding of climate change? Why or why not?

Now read this definition:

Climate change refers to changes in the measures of Earth’s climate over a long period of time including weather, precipitation, and temperature patterns, primarily caused by human activities.

In what ways does adding “human activities” change your understanding of climate change? Is there anything you feel is missing from this definition? Is there anything you feel should not be included?

Share your responses with a friend or classmate, or [[☃ explanation 2]]

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Are they liars or just uninformed? People are getting way too good at presenting opinion as fact. Luckily, claim testers help us get to the bottom of just about anything.

Learning to test claims will help you evaluate evidence and arguments about climate change. We'll learn about four claim testers in this activity: intuition, logic, authority, and evidence.

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Key information

A claim is a statement or main point that someone believes to be true. Here's an example of a claim:

School should start later i the morning so that students can get more sleep and be more alert.

A counterclaim is an argument that goes against or disagrees with the main poin or claim someone else has made. Here's an example of counterclaim:

School starting later would make it more challenging for students with jobs or extra-curricular activities they do after school.

Claim testers help us assess the reliability of claims. Click on each claim tester below to learn about them.

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Intuition and logic can help us make quick assessments by drawing on past experiences, gut feelings, and our sense of whether something fits with what we already know. Authority and evidence are tools we use to look behind the information and interrogate the truth and reliability of a claim.

Identifying claims

Let's practice testing claims. Read the following paragraph and underline the claim being made.

The Earth’s temperature always goes up and down in a natural pattern. This change has been driven by geophysical factors like volcanic activity, solar radiation, and changes in the Earth’s orbit. NASA (National Aeronautics and Space Administration) reports that over the last 800,000 years, there have been eight cycles of ice ages and warmer periods. This probably fits with what you know about our planet’s history—you don’t see any woolly mammoths around today! For example, data shows that in the year 539 or 540 CE, the Ilopango volcano in El Salvador erupted violently. Volcanic sulfur from the eruption triggered a roughly 2-degree Celsius temperature drop that lasted 20 years.

Now, let's break it down and look at specific statements. Identify which claim testers are at work within each statement.

Remember: the claim testers sometimes overlap and work togeter. But for this activity, pick the strongest one and jot it down or use the dropdown menu to select it; your responses aren't graded.

• This change has been driven by geophysical factors like volcanic activity, solar radiation, and changes in the Earth’s orbit. [[☃ dropdown 4]]

• NASA (National Aeronautics and Space Administration) reports that over the last 800,000 years, there have been eight cycles of ice ages and warmer periods. [[☃ dropdown 5]]

• This probably fits with what you know about our planet’s history—you don’t see any woolly mammoths around today! [[☃ dropdown 6]]

Why did you pick those claim testers for each sentence? For each statement, write a sentence explaining why you chose that claim tester.

Evaluating claims

Do you agree with the claim being made in the paragraph above? Why or why not? Be sure to use the claim testers in your response.

Next, try to come up with statements or counterclaims that might help [[☃ definition 2]] the claim that the Earth’s temperature always goes up and down in a natural pattern.

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Share your responses with a friend or classmate, or [[☃ explanation 2]]

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##How Do We Know Climate Change Is Real?

By Bennett Sherry

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Introduction

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How do we know [[☃ definition 1]] is happening? It’s a simple question, but there are a lot of conflicting viewpoints and people out there trying to convince you one way or the other. Some, such as people in the [[☃ definition 2]] industry, might want to convince you that climate change isn’t real, or that human activity isn’t what’s causing it.

Here’s the truth: The vast majority of scientists claim that climate change is happening, and that humans are causing it. Scientists have come to this conclusion by examining the huge amount of climate data we now have access to. This data suggests that human emissions of [[☃ definition 3]]—such as carbon dioxide (CO$_2$)—are causing global temperatures to rise more rapidly than at any point in the last century. We also have overwhelming evidence that the oceans are getting warmer and more acidic, ice sheets and glaciers are shrinking, sea levels are rising, and that extreme weather events are increasing in frequency as a result of these rising temperatures.

Humans have only had the tools to measure $CO_2$ levels for the last hundred years or less, but thanks to technologies that let us analyze ice cores, ocean sediment, tree rings, and more, scientists have been able to collect data that stretches back hundreds of thousands of years. This data tells us that our current rate of warming is not part of a natural cycle. The climate is changing rapidly and in ways unlike anything that’s happened in hundreds of thousands of years. Climate change is happening, and it’s driven by human activity. How can we say this with such certainty? Let’s explore the connections between data on rising temperatures and data on atmospheric concentrations of $CO_2$.

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Is it hot in here, or is it just me?

It’s not just you! Earth is heating up at an alarming rate. Chart 1, on the next page, measures the global monthly temperature anomaly since 1880. Temperature anomaly is a way of measuring the increase or decrease in temperature from a baseline average. This chart uses the average monthly temperature from 1951 to 1980 as its baseline. You can see from this chart that, particularly in the last 50 years, global temperatures have increasingly risen above the baseline. In recent years, temperatures have peaked above 1 degree Celsius over the baseline. Looking back to 1880, you can see that temperatures were often below the baseline. The world is warmer than it was just 50 years ago and significantly warmer than in the nineteenth century. A 1-degree Celsius increase might not seem like much, but as you’ll learn in the coming lessons, seemingly minor changes in global average temperatures will have disastrous impacts in many parts of the world. The rise in global temperatures is what is driving all the other indicators of climate change—including ice melt, sea-level rise, and extreme weather events.

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Greenhouse gas emissions

Scientists believe that the rapid warming illustrated by Chart 1 is a result of emissions of greenhouse gases into Earth’s atmosphere by humans. Greenhouse gases such as carbon dioxide, methane, and nitrous oxide trap heat from the Sun inside Earth’s atmosphere. Carbon dioxide is—by far—the most abundant greenhouse gas that’s released by human activity, particularly the burning of fossil fuels. Chart 2 illustrates the change in the amount of $CO_2$ that has been emitted globally since 1750. Soon after 1750, with the start of the Industrial Revolution, human societies increasingly burned fossil fuels to power machines. Burning fossil fuels like coal, oil, and natural gas for energy releases large amounts of $CO_2$ into the atmosphere. Chart 2 indicates that, before the Industrial Revolution, $CO_2$ emissions were very low. From 1950 to the present, as the population of Earth tripled and we used ever more fossil fuels to power modern life, $CO_2$ emissions have skyrocketed.

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Earth has been around for a long time. A really long time. Four-and-a-half billion years long. And Chart 2 only shows the last 275-ish years. So how do we know that this level of carbon in the atmosphere is actually a big deal? After all, there’s evidence that there have been plenty of ice ages and warming periods during the 2 million years of human existence. Yet, as Chart 3 shows us, we have data on $CO_2$ levels from ice core samples—data that goes back 800,000 years. In this chart, you can see that in the past century—a century of rapid technological development that saw humanity embrace fossil fuels—the concentration of $CO_2$ in Earth’s atmosphere has reached unprecedented levels. This is a strong indication that humans are transforming our atmosphere far beyond any natural cycle.

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Combining data

We know from Chart 1 that global temperatures have been rising in the last century. We also know from Charts 2 and 3 that $CO_2$ emissions have risen dramatically thanks to human industrialization and the burning of fossil fuels. How are the two trends related, and what does it mean for the future of climate change? One of the most important skills we can develop to become adept at reading data is the ability to compare two different sets of information, and then make correlations between them. By doing this, we gain a deeper understanding than when we look at only one set of data. Take a look at Chart 4, below. This chart shows both temperature anomaly and $CO_2$ atmospheric concentration over the last 800,000 years. What does this chart suggest about the relationship between global warming and $CO_2$ in Earth’s atmosphere? Finally, what does this chart (in particular, the point labeled “Today”) suggest about the future of climate change?

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Conclusion

So, how do we know climate change is real? And how do we know it’s caused by human activity? From the four charts we’ve just examined, there are a few conclusions we can draw:

• Earth’s temperature is rising at a rate unprecedented in the last 150 years.
• There is more $CO_2$ in our atmosphere than any time in the last 800,000 years, and the dramatic increase in the last century suggests that human activity is responsible.
• Data from the last 800,000 years shows us that there is a strong correlation between the concentration of $CO_2$ in our atmosphere and rising global temperatures.

In short, climate change is real. It’s happening. And humanity’s use of fossil fuels is to blame.

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##Author bio

Bennett Sherry

Bennett Sherry holds a PhD in history from the University of Pittsburgh and has undergraduate teaching experience in world history, human rights, and the Middle East at the University of Pittsburgh and the University of Maine at Augusta. Additionally, he is a research associate at Pitt’s World History Center. Bennett writes about refugees and international organizations in the twentieth century.

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Claim Testing – Earth's Climate Record

Now that you've read "How Do We Know Climate Change Is Real?", practice your claim-testing skills by evaluating what you read and making a claim of your own.

1. The author makes this claim:

Here’s the truth: The vast majority of scientists claim that climate change is happening, and that humans are causing it.

The author supports his claim with the following statement:

Scientists have come to this conclusion by examining the huge amount of climate data we now have access to. This data suggests that human emissions of greenhouse gases—such as carbon dioxide (CO2)—are causing global temperatures to rise more rapidly than at any point in the last century.

What claim testers can you identify in the supporting statement? Pick at least one claim tester.

2. Now, let's take a moment to review the course definition of climate change:

Climate change refers to changes in the measures of Earth’s climate over a long period of time including weather, precipitation, and temperature patterns.

Find and write down at least one statement from the article you read which supports this definition.

3. You've probably noticed that his article is full of claims using evidence and authority. Can you find any examples of logic or intuition being used in the article?

4. Next, write your own claim about how we know climate chage is real. Be sure to support it with one piece of evidence from the article.

Share your responses with a friend or classmate, or [[☃ explanation 1]]

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You've learned a lot about what climate change is and practiced testing different claims about climate change. Now, you'll make your own claim about what a future with climate change might look like.

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##Review the claim testers

Before we dive into the actvity, quickly check your understanding of the claim testers.

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Climate change will...

1. Write a claim that completes the sentence below:

Climate change will...

2. Write two or three sentences explaining why you made that claim.

3. What claim tester or testers (authority, evidence, logic, intuition) would you use to defend the claim you made? Why?

What did you write? Share with a friend or classmate, or you can [[☃ explanation 1]]

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