Skip to main content

PWS 180: Section 3

How does human activity alter the climate system?
The worksheets, slides, and other materials for this section can be found in this Box folder: PWS180 shared.

Now that you know the primary controls on the Earth’s climate, we now are going to focus on what human activities are affecting the climate system. We will spend the next few weeks exploring how humans have already affected the atmosphere, land, and ocean, as well as what we know about the future trajectory of the Earth system.
  • This week, we are moving beyond how the Earth’s climate has worked before humans came on the scene. Starting a few hundred years, humans started influencing climate on a global scale. We will go over some of those early examples of human-climate interactions and read the most updated version of the extent of our interference today. There are fewer readings than usual, but they are somewhat longer. As always, take your time and ask questions in and out of class:

    1. Reading: Essay by Charles C. Mann on the “State of the Species.” This article takes an unconventional view of our status on planet Earth and the prospects for our future.
    2. Reading: BBC coverage of an important article on how European colonization of the Americas triggered a chain of events that contributed to the Little Ice Age.
    3. Reading: Introduction to the IPCC assessment report structure and terminology by the Carbon Brief.
    4. Reading: The Introduction and Part A of the IPCC Sixth Assessment Report (AR6), Summary for Policy Makers (SPM). This is from pages SPM-4 to SPM-14. You can download the report here or access the pdf in the shared Box folder. This is a highly condensed version of a 3,949-page report! Don't be intimidated, you are now a climate expert! If you have questions about terminology or concepts in the SPM, feel free to dip into the full report for much more explanation, graphs, and references.

    Here are some additional readings for those who want to dig deeper:

    • The original, 2019 article by Koch and others on the Great Dying and its effects on climate (if you don’t have access, the pdf is in the shared folder).
    • A nice, nontechnical overview by Katherine Hayhoe of what is changing in the Earth’s climate and why a “few degrees” matters.
    • Carbon Brief description of how AR6 is different from AR5.
    • Full IPCC AR6 report.

    Questions to guide (or at least to start) your reading:

    1. In Charles Mann’s article, why does Lynn Margulis say that the fate of every successful species is to wipe itself out?
    2. What do you think changed in humankind that allowed us to expand from our very small initial range ~100,000 years ago to begin filling the world ~50,000 years ago?
    3. Why do some paleontologists and evolutionary biologists think that all humans are so genetically similar?
    4. Biologically, why is there such a drive to consume and reproduce?
    5. Population growth of any species sometimes follows an “S” curve. What causes the two inflection points in that shape (i.e. why does growth accelerate so much and why does it eventually decelerate)?
    6. What is behavioral plasticity, and how does it relate to the future success or collapse of human civilization?
    7. How are population growth and consumption (total and per-capita) linked?
    8. In what ways is the task of constraining or directing human growth “unnatural” or surprising?
    9. How might the decline of slavery, misogyny, violence, and other forms of oppression inform our thinking about change in modern consumption and production patterns?
    10. What caused the “Great Dying” of indigenous people in the Americas during the 16th century?
    11. What did this continental catastrophe trigger in the terrestrial ecosystems and subsequently the atmosphere?
    12. The IPCC report defines risk as a product of hazard, vulnerability, and exposure. What does this mean?
    13. T/F High risk occurs when you have high probability outcomes with severe consequences.
    14. How does the IPCC assign different levels of certainty (likelihood) to the research it synthesizes?
    15. How much has global temperature changed since 1850?
    16. How much has minimum Artic Sea Ice changed since 1900?
    17. T/F Sea level has not yet changed since 1900, but if warming continues, it could rise substantially
    18. How much of the extra heat caused by anthropogenic climate change is in the atmosphere versus the ocean?
    19. What are the four most important anthropogenic greenhouse gases?
    20. How much is a gigaton of carbon? How does it relate to a gigaton of CO2?
    21. Globally, what economic sectors produce the most greenhouse gas?
    22. How can greenhouse gases account for more than the warming we have observed?
    23. T/F Climate change is primarily of concern because it could push certain vulnerable species over the edge.
    24. What is the difference between mitigation and adaptation regarding climate change?
    25. What is the cryosphere and why is it important to current human society?
    26. Because the IPCC summary has to be approved line-by-line by delegates, how might this influence the content and tone of the SPM?
  • This week, we are focusing on how human activity is reshaping the atmosphere and the climate system. What activities are causing the changes, how do we know it’s humans, and which humans are contributing the most?

    1. Reading: Part B of the IPCC Sixth Assessment Report (AR6), Summary for Policy Makers (SPM). This is from pages SPM-15 to SPM-30. You can download the report here or access the pdf in the shared Box folder.
    2. Reading: The Wikipedia article on Global Warming Potentials. In typical Wikipedia style, this article efficiently presents the main concepts surrounding how we compare different greenhouse gases. This is a complex subject, but really important moving forward.
    3. Watching (5 minutes): The Denial 101 episode on Consensus of Evidence. This episode succinctly summarizes some of the ways we know that greenhouse gas increases and consequent warming are due to humans.
    4. Watching (9 minutes): Katherine Hayhoe on Fossil fuels and renewable energy. This episode explains how important fossil fuels have been in the past, and why it is so important that we transition to better sources of energy for the future.
    5. Reading: The World Resources Institute’s greenhouse gas emissions by countries and sectors. This WRI report provides detailed information about the sources of greenhouse gases. You could spend hours with their interactive figures and learn a lot. For the purposes of this week, focus on what economic sectors and what countries are producing the most greenhouse gases.
    6. Reading: The US Environmental Protection Agency’s webpage on sources of greenhouse gas emissions in the U.S. The EPA’s webpage is a clear and direct dashboard for emissions in the US. Feel free to click on the different tabs to get more detail about each sector.
    7. The explainer on the UN Climate Change Conference of Parties (COP), which starts in just a few weeks!

    Additional readings:

    • Kate Marvel interview on the Ezra Klein show on climate models, uncertainty, and how to understand climate change. This interview is pretty wide ranging, and Dr. Marvel  goes into projections of future climate and potential individual and political responses to those changes. However, I think that Dr. Marvel does a marvelous job at making technical climate simulations understandable, and I think this interview provides an interesting starting point for the rest of the semester.
    • The Skeptical Science article on attributing climate change to human activity.
    • The full Global Carbon Budget for 2019. This is the most comprehensive summary of the sources and sinks of greenhouse gases on Earth.
    • The US EPA’s description of Global Warming Potential for various greenhouse gases.
    • An article by Dr. Michelle Cain on some of the drawbacks of a static conversion among greenhouse gases.
    • The Global Carbon Budget summary highlights. We will be reading full articles by the Global Carbon Project soon, but this week we are focusing on the summary updates for 2019. The article is very short but stuffed full of important information about the state of the carbon cycle.
    • Short film about Eunice Newton Foote, the first researcher to demonstrate the heat-trapping capacity of CO2.
    • Reading: Wikipedia article on the Paris Agreement
    • ReadingPeters et al. 2019. This article from the journal Nature Climate Change reports the detailed results of the Global Carbon Project’s 2019 report. Pay attention to how different sectors of fossil fuel are changing and in what regions the changes are happening. (PDF in the shared folder, if you don’t have access)
    • ReadingJackson et al. 2019. This article from the journal Environmental Research Letters compares greenhouse gas emissions with commitments from the Paris Agreement. Pay special attention to the global and regional trends over the past 20 years in greenhouse gas emissions.
    • WatchingGlobal Weirding video on background on fluorinated gases, ozone, and climate change by Katherine Hayhoe. This video links a major environmental success (combatting the ozone hole) with current efforts to reduce greenhouse gas emissions.
    • Reading: The announcement and text of the Paris Agreement
    • Watching: The announcement by President Trump that the U.S. was pulling out of the Paris Agreement. Official transcript here.
    • Reading: News coverage from The Guardian of greenhouse gas trends compared to Paris Agreement
    • ReadingNational Geographic coverage of successful and failing grades given to different countries for their climate action.

    Questions to guide (or at least initiate) your reading and thinking:

    1. What is a climate model?
    2. What is climate sensitivity?
    3. How do we know that the increase in greenhouse gases and consequent warming are due to humans?
    4. What are CO2 equivalents and why do we use such convoluted units to understand greenhouse gas emissions?
    5. What is “global warming potential,” and why is it so different depending the gas and the timescale chosen?
    6. What was the total amount of greenhouse gases produced by humankind in 2019?
    7. At a global scale, what sectors of the economy are contributing the most to climate change?
    8. Are the same emissions patterns true within the U.S.?
    9. T/F Fossil fuels have always been a negative factor in human development.
    10. What percentage of cumulative greenhouse gas emissions have been produced by the U.S.?
    11. What percentage of current greenhouse gas emissions are produced by the U.S.?
    12. What are the global trends in greenhouse gas emissions over the past 50 years?
    13. What factors are preventing global greenhouse gas emissions from falling enough to meet the Paris Agreement?
    14. What countries are the biggest contributors of greenhouse gases?
    15. What are the trends of greenhouse gas emission for those countries?
    16. How much of an effect do you think the U.S. retraction from the Paris Agreement had on national and global climate response?
    17. How are the ozone hole and climate change connected?
    18. What is an example of solving a global environmental problem, or are we doomed to fail?
    19. T/F Fossil fuels have always been a net negative factor in human civilization.
    20. What are some proposed mechanisms for meeting the Paris Agreement?
    21. What is your sense for what the scientific authors we read this week believe about the prospect of limiting climate change to 2C or 1.5C (i.e. are they optimistic or pessimistic)?
    22. What is the UN trying to achieve with COP26?
  • This week, we are focusing on how climate change affects ecosystems, including the humans that live within them. As you go through the readings below, try to organize your notes around the following themes: 1. Human health and wellbeing, 2. Human economy, 3. Biosphere integrity, 4. The Earth’s biogeochemical cycles. There are many excellent resources on this topic, and I encourage you to read a variety of sources in addition to the required readings below. Remember that it is easy to find extreme examples (in both directions). Consider the strength of all the claims you encounter and try to develop a comprehensive and critical view of what climate change means and could mean. As always, take your time and ask questions in and out of class:

    1. Reading: JP Morgan Chase is one of the largest investment banks in the world. They are also the single largest funder of fossil fuel projects. The multinational bank assigned two of their economists to summarize climate science in an internal report for shareholders. Basically, they wanted to know how serious of a threat climate change was, and how badly might it affect the economy. In January of 2020, the report was circulated privately to board members, but it was obtained and leaked by the climate activist group Extinction Rebellion. The report provides a succinct overview of the causes and consequences of climate change. Because it was intended as an internal document, it gives a direct and unapologetic assessment of the risks of climate change. JP Morgan Risky Business.
    2. Watching: This nontechnical overview by Katherine Hayhoe describes what is changing in the Earth’s climate and why a “few degrees” matters. After watching this general video, watch one or more of the videos below, which describe regional impacts across the US and Canada. If you are from the US or Canada, pick the region closest to where you are from, and if you are not, pick the region that most resembles where you are from.
      1. Reading: In 2020, more than 11,000 scientists (including myself) signed on to the World Scientist’s Warning of a Climate Emergency. This short document provides an evidence-based, clear language warning of the consequences of climate change.
      2. Watching: This video by Climate Denial 101 is bland but brutal with details and some useful framing about present and future climate change.

      Here are some additional readings for those who want to dig deeper:

      Questions to guide (or at least to start) your reading:

      • Is climate change an existential threat for humanity?
      • How do the hazards and negative consequences of climate change increase or decrease with more extreme warming (e.g. 1.5 versus 2.0 C of warming)?
      • Approximately how much has the Earth warmed since the Industrial Revolution?
      • How will climate change affect the area that you are from?
      • How has climate change already affected your region?
      • What are some of the most important consequences of climate change for
        • Human health and wellbeing
        • Society (economy, national security, etc.)
        • Biosphere integrity
        • The Earth’s great biogeochemical cycles (e.g. water, carbon, nitrogen, phosphorus)
      • What is the difference between mitigation and adaptation regarding climate change?
      • Compared to the authoritative reports you read (IPCC and NCA), do you find that media coverage of climate change tends to exaggerate or downplay the consequences of this issue?
      • T/F If we limit warming to 1.5 degrees, we will avoid the negative consequences of climate change.
      • T/F Climate change is primarily important because of how it threatens vulnerable species.
      • People often bring up examples of how climate change could bring about positive changes. Are they completely wrong and how would you respond to this line of reasoning?
      • What are the four ecological laws and how do they relate to the consequences of climate change?