Human activities are impacting the climate system.

These key ideas relate to the causes and effects of human-induced climate change.

The potential for human activities to increase the temperature of the Earth through greenhouse gas emissions has been described and calculated for over a century. Volumes of scientific research across multiple scientific disciplines agree that humans are warming the climate, and the IPCC Sixth Assessment Report states, "Human activities, principally through emissions of greenhouse gases, have unequivocally caused global warming." (From the IPCC AR6)

There is overwhelming evidence that human activities, especially burning fossil fuels, are leading to increased levels of carbon dioxide and other greenhouse gases in the atmosphere, which in turn amplify the natural greenhouse effect, causing the temperature of the Earth's atmosphere, ocean, and land surface to increase. Greenhouse gases "trapping" infrared heat is well established through laboratory experiments going back to 1856 when Eunice Foote first measured the effect.

The well-documented trend of increasing CO₂ in the atmosphere is caused by the burning of fossil fuels and massive land cover changes. The "smoking gun" that shows clearly that human activities are responsible for recent increases in carbon dioxide in the atmosphere is provided by carbon isotopes (carbon atoms of different atomic weights). These isotopes allow scientists to "fingerprint" the source of the carbon dioxide molecules, which reveal that the increased CO₂ in the atmosphere is caused by fossil fuel burning (see references).

The human causes of climate change are some of the most important concepts to teach

Due to the basic physics of heat-trapping gases and an exponential rise in population and energy consumption, humans have become a force of nature. Clearly, this is a topic with enormous political, socio-economic, and emotional dimensions, but the scientific results show clearly that:

• Human activities, particularly the combustion of fossil fuels, are altering the climate system.
• Human-driven changes in land use and land cover such as deforestation, urbanization, and shifts in vegetation patterns also alter the climate, resulting in changes to the reflectivity of the Earth's surface (albedo), emissions from burning forests, urban heat island effects, and changes in the natural water cycle.
• Because the primary cause of recent global climate change is humans, the solutions are also within the human domain.
• Because we understand the causes of climate change, that paves the way for effective solutions to be developed and deployed. (Learn more about teaching about solutions.)
  

Helping students understand these ideas

The human impact on climate change is the most frequently misunderstood aspect of climate science. Some sectors of the public continue to debate whether these ideas can be true, despite well-established science. There are several possible reasons why students may resist the conclusion that humans are altering the climate. This concept may be uncomfortable to students due to feelings of guilt, political resistance, or a genuine lack of scientific understanding. Furthermore, projections of the effects of climate change on our society can frighten, overwhelm, or discourage students. This can result in denial or resistance to learning. Furthermore, even if a student possesses a firm grasp of this topic, it is nearly certain that at some point this knowledge will be challenged outside of class. Building a solid and careful scientific argument is essential. For more on climate change and mental health, see the CLEAN Climate Mental Health pages.

Educators are encouraged to introduce this topic with generous scaffolding that establishes the foundations of the process of science, the underlying principles of climate science, and a reliance on the robust scientific research that supports this conclusion. Several strategies are presented on this page about Teaching Controversial Environmental Issues which emphasizes the affective and emotional aspects of student learning.

It may be tempting to have a debate about this topic, but that may not be the most effective way to characterize it. A debate suggests that there are two credible, opposing viewpoints, when in fact the scientific community is virtually unanimous about the human causes of climate change. Secondly, debating a topic can reinforce misconceptions and cause unnecessary controversy in the classroom. That said, careful discussion of diverse viewpoints is absolutely essential. Role-playing can be one way to represent broad perspectives while maintaining scientific accuracy.

Bringing these ideas into your classroom

Even though this topic can be a sensitive one, it is also an essential facet to understanding climate change. Educators are urged not to shy away from the human role in shaping the climate, but instead to approach it in a deliberate manner, with pacing and framing intentionally designed to help your students understand the science and reconcile the meaning.

• When possible, use data-driven explanations.
• Avoid assigning blame or judgment. 
• Weave pathways to action into the discussion every step of the way. This prevents feelings of hopelessness and also shows the scientific and technical responses that are needed to curb the worst effects of climate change.
• Foster a classroom environment where all perspectives are welcome. Invite students to voice their doubts, fears, or uncertainties. (Learn more about creating a validating classroom environment.)

Teaching materials from the CLEAN collection

Middle school

• Using the Very, Very Simple Climate Model in the Classroom helps students learn about the connection between CO₂ emissions, CO₂ concentration, and average global temperatures.
• Students can learn about the Keeling Curve and its famous data with this graphing exercise: Our Changing Atmosphere.
• NASA's World of Change animation shows deforestation in Brazil. Loss of productive forests is another contributor to human-caused climate change.
• Climate Change Basics video offers a simple and easy-to-understand overview of climate change and its causes.
• The Fifth National Climate Assessment summarizes the impacts of climate change on the United States, now and in the future. The report can be explored by region and uses clear, simple messages to streamline the findings.

High school

• Climate Change and the Carbon Cycle - This unit introduces high school students to climate change, the carbon cycle, and the effects of increasing atmospheric carbon dioxide on Earth's climate.
• Climate scientist Richard Alley summarizes the case for human-caused climate change in this video segment, It's Us.
• Debunking Cranky Uncle on the carbon cycle - This video illustrates the Keeling curve as evidence to establish man's role in global climate change.
• Next Generation Climate Lesson 2 - What factors have caused the rise in the global temperature over the last century? - In this activity, students explore factors that have caused the rise in global temperature over the last century. Educators have the opportunity to assess how modeling activities (the game), analogies (the cake), and mathematical models (graphs) develop and change student mental models.

College

• The activity Global Climate Change: The Effects of Global Warming examines trends in carbon dioxide emissions and considers the human influences on atmospheric carbon dioxide concentrations.
• Using a mass balance model to understand carbon dioxide and its connection to global warming allows exploration of increasing atmospheric carbon dioxide and carbon emissions.
• Students can explore data-driven questions about economies, populations, energy, and emissions with Gapminder: Unveiling the beauty of statistics for a fact-based world view.
• Mann and Ramsdorf on IPCC 2013 features well-known climate scientists discussing public perceptions of climate science.
• Because this particular fact of climate change is often misunderstood, activities such as Is That True? and Effectively Engaging with Climate Skeptics can help students navigate misinformation.