CLEAN > Teaching Climate and Energy Science > Teaching Climate Science > 6. Humans Affect Climate

Teaching about the human impacts on climate is supported by five key concepts:

Teaching this principle is supported by five key concepts: a. The overwhelming consensus of scientific studies on climate indicates that most of the observed increase in global average temperatures since the latter part of the 20th century is very likely due to human activities, primarily from increases in greenhouse gas concentrations resulting from the burning of fossil fuels.

b. Emissions from the widespread burning of fossil fuels since the start of the Industrial Revolution have increased the concentration of greenhouse gases in the atmosphere. Because these gases can remain in the atmosphere for hundreds of years before being removed by natural processes, their warming influence is projected to persist into the next century.

c. Human activities have affected the land, oceans, and atmosphere, and these changes have altered global climate patterns. Burning fossil fuels, releasing chemicals into the atmosphere, reducing the amount of forest cover, and the rapid expansion of farming, development, and industrial activities are releasing carbon dioxide into the atmosphere and changing the balance of the climate system.

d. Growing evidence shows that changes in many physical and biological systems are linked to human caused global warming. Some changes resulting from human activities have decreased the capacity of the environment to support various species and have substantially reduced ecosystem biodiversity and ecological resilience.

e. Scientists and economists predict that there will be both positive and negative impacts from global climate change. If warming exceeds 2 to 3°C (3.6 to 5.4°F) over the next century, the consequences of the negative impacts are likely to be much greater than the consequences of the positive impacts.

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 2013 IPCC Forth Assessment Report states, "Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system." (From the IPCC AR5, FAQ brochure)

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. That greenhouse gases "trap" infrared heat is well established through laboratory experiments going back to the mid 1850s when Sir John Tyndall first measured the effect.

The well-documented trend of increasing of 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 weight). 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 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 human, 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 the 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 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.

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 judgement. As atmospheric scientist Scott Denning puts it, CO2 traps heat "because of its molecular structure, not because capitalism is evil. It's just bad luck!" (Scott Denning Research Group, ppt for Engaging Hostile Audiences)
  • Weave solutions 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

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2014 National Climate Assessment Report 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.

2013 IPCC Summary for Policymakers steps through the causes, effects, and impacts of climate change. See also the FAQ brochure (pdf) which is less technical.

And older, but still accurate IPCC document from 2007 also addresses this question: How do Human Activities Contribute to Climate Change and How do They Compare with Natural Influences?

How do we know that recent CO2 increases are due to human activities? - a scientific summary from

The human fingerprint in coral - This page from the Skeptical Science website provides clear answers to common questions and misunderstandings about climate change.

Solar Variability & Global Climate Change - This summary from the Standford Solar Center describes the relationship between sunspots, solar irradiance and climate change

New statistical analysis confirms human role in climate change - A summary of physics research that uses a simple, statistical approach to understand causes of climate change.

Causes of Climate Change - This NASA web page describes the greenhouse effect, the role of human activity and the evidence that changes in solar irradiance are not related to recent temperature increases.

Global Warming's Six Americas - This ongoing project tracks Americans' opinions and beliefs about climate change. This approach identifies six unique audiences within the American public that each responds to the issue in their own distinct way. This is a great way to learn about the possible audiences among your student population.

Examining the Scientific Consensus on Climate Change, P. Doran, M. Zimmerman. EOS, Transactions American Geophysical Union, 2009, vol. 90, no. 3, p. 22, 200. This article compares the consensus views of scientists and the general public on climate change.

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