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College of Life Sciences Plant and Wildlife Sciences
Ben Abbott Lab
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PWS 180: Section 2

What controlled Earth's climate in the past?
The worksheets, slides, and other materials for this section can be found in the Box folder (link in syllabus).

  • This week, we will dive into the workings of the Earth’s climate system. For most of you, there will be a lot of new terminology and concepts. Several of the readings cover similar material, but in different ways and from different perspectives. I recommend following the order below, which generally moves from the more basic to the more advanced. Take your time and ask questions in and out of class:

    Watching (2 minutes): Neil de Grasse Tyson on weather and climate (excerpt from the reboot of the series “Cosmos”)
    Reading: Wikipedia article on Earth’s Energy Balance (this is dry and somewhat technical, but packed with important stuff)
    Reading: Skeptical Science article “What does past climate change tell us about global warming?” (I really like this website, which I have found to be highly reliable and practical. Click on any of the underlined words, and it will show you a definition. You can also switch to a more basic version of the article with the tab at the top, if you are struggling with the content).
    Watching (10 minutes): An episode from the online course Denial 101 on understanding the past of Earth’s climate.
    Watching (5 minutes): Another Denial 101 episode on Reinforcing Feedbacks by Professor Sarah Green.
    Reading: Paul Loubere “The Global Climate System” (This is a great resource of technical and fact-checked articles on multiple natural science topics).

    Here are some additional readings if you want to get into it more:

    Here are some questions to guide your study:

    • What are the units of time in geological terms? Order the following divisions of time from longest to shortest.
      • Eons, Ages, Supereons, Periods, Eras, Epochs
    • What is our current Era and Epoch?
    • Are we living in an ice age?
    • What are some of the distinct climate periods in recent history (e.g. last 2000 years)?
    • What is the difference between weather and climate?
    • Given its distance from the sun, why isn’t the Earth frozen solid?
    • If you had to identify four major controls on the Earth’s climate before the industrial revolution, what would you list?
    • What is the lower part of the atmosphere called that we interact with personally?
    • How is the lower part of the atmosphere warmed?
    • How is energy redistributed in the Earth system and how is that redistribution affected by the spinning of the planet?
    • As air warms, its ability to hold water increases or decreases? What is the shape of this relationship?
    • Why doesn’t evaporation lead to a runaway greenhouse gas effect on Earth?
    • How is temperature in the upper atmosphere changing and why?
    • What are some stabilizing and destabilizing feedbacks in the Earth’s climate system? Note: these feedbacks are often called negative and positive feedbacks, but I find the terms stabilizing and destabilizing more intuitive.
    • What are teleconnections?
    • In what ways does water shape the Earth’s climate?
    • What is the form of most of the solar energy that reaches Earth’s atmosphere from the sun: long wave, short wave, new wave?
    • What caused the cold periods (known as ice ages) in the past million years?
    • T/F The Earth’s climate system is nearly in equilibrium?
    • T/F There is often a time lag between changes in the Earth’s surface temperature and changes in Earth’s energy balance.
    • What is the largest “buffer” (stabilizer) of the Earth’s surface temperature?
    • What is the solar constant and how much has it varied in the past several centuries?
    • How much of the Earth’s energy budget comes from geothermal heat?
    • What is the difference between variation (change in different regions) and coherence (a trend)?
    • Which of the following best describe current warming compared to paleoclimate:
      • Typical for the Holocene (last 12,000 years)
      • Somewhat different than the Holocene
      • Similar to several events in the last million years
      • Similar to several events in the last tens of millions of years
      • Unprecedented in the Earth’s history

  • This week, we are going to dig into some broader aspects of the climate system, as well as explore the tools that scientists have used to generate this understanding. We are coming up on a test, so I’ve lightened up the load. There are still seven items, but I bet you can work through them all in under 2 hours.

    1. Watching (7 minutes): South Central Climate Adaptation Science Center’s video on The Earth’s Energy Budget. This will give another overview of how energy enters and cycles through the Earth system.
    2. Watching (15 minutes): “Climate Literacy” video on Ice ages. This video provides great context and learning activities to understand how orbital factors have influenced climate in the Holocene and beyond.
    3. Reading (10 minutes): Wikipedia article on abrupt climate change in the past. You can start at the “Possible precursor” section and read to the end. This will provide brief descriptions of past climate change and their consequences for ecosystems on Earth.
    4. Watching (10 minutes): “SciShow” introduction to Mass Extinctions and the role of paleoclimate change in these events. This video goes over the five major mass extinctions (times when 50% or more of the Earth’s species went extinct). There is a lot of information presented in a rapid format, but try to tease out how much of a role paleo climate change played in these events.
    5. Reading (15 minutes): USGS paleoclimate proxies. Now we are going to get into how we know what we know about paleoclimate. This is a dry but helpful glossary of different types of paleo proxies. You don’t need to memorize each type of proxy but be familiar with the various categories and examples of how they help us reconstruct climate.
    6. Reading (17 minutes): Zeke Hausfather on What Greenland ice cores say about past and present climate change. This article zooms in on a specific story of one type of climate proxy: ice cores. It traces not only the scientific information generated by ice cores, but also the misinterpretation of these records by groups skeptical of the scientific method.
    7. Watching (8 minutes): Katherine Hayhoe on Climate Models. This is a nontechnical summary of how climate models work from a top climate change researcher. Dr. Hayhoe’s “Global Weirding” series provides great context and clear answers about climate change questions.

    Here are some additional readings if you want to get into it more:

    Here are some questions to guide your study:

    1. What have been the most abrupt examples of climate change in the Earth’s history?
    2. What caused those paleoclimate changes (e.g. how much was due to ecosystem feedbacks, physical processes in the Earth system, changes beyond the Earth)?
    3. What were the consequences of the climate changes for ecosystems and biodiversity?
    4. What are the long-term processes that regulate Earth’s climate (i.e. what are the stabilizing feedbacks that keep the Earth from careening off into snowball or hothouse states)?
    5. Give an example of a stabilizing and a destabilizing ecosystem feedback?
    6. How do we even know about the Earth’s past climate, when reliable temperature and precipitation data have only been available for the past few centuries?
    7. T/F We can reconstruct the past climate with a high level of confidence from individual proxies
    8. What do eccentricity, axial tilt, and precession mean and how do they affect climate?
    9. What is the solar constant and how much has it changed in the recent past?
    10. What role have the Earth’s oceans played in paleo climate?
    11. Give one example of each of the following types of climate proxies:
      1. Physical
      2. Chemical
      3. Biological
    12. What makes one element different from another (e.g. the number of protons, neutrons, or electrons)?
    13. What is an isotope of an element?
    14. What is a climate model (also called a general circulation model, a global climate model, or an earth system model)?
    15. How can we evaluate if a climate model is accurate or useful?

  • This week, there are no readings! Just prepare for the first midterm. We will still have a lecture on Monday to finish up the materials from Section 2, but there are no required readings and there is no worksheet.

    Instead, check out this awesome bicycle videos: