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Earth's Changing Climate

Earth's Changing Climate

Professor Richard Wolfson Ph.D.
Middlebury College
Course No.  1219
Course No.  1219
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Course Overview

About This Course

12 lectures  |  30 minutes per lecture

In 2007 the Intergovernmental Panel on Climate Change concluded that "warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level." Representing a consensus of hundreds of scientists, the report went on to note that human activity is "very likely" the cause.

This course of 12 half-hour lectures reviews the most up-to-date research on climate change, explaining the concepts, tools, data, and analysis that have led an overwhelming number of climate scientists to conclude that Earth is warming and that we humans are in great part responsible.

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In 2007 the Intergovernmental Panel on Climate Change concluded that "warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level." Representing a consensus of hundreds of scientists, the report went on to note that human activity is "very likely" the cause.

This course of 12 half-hour lectures reviews the most up-to-date research on climate change, explaining the concepts, tools, data, and analysis that have led an overwhelming number of climate scientists to conclude that Earth is warming and that we humans are in great part responsible.

Behind the Consensus

Whatever your views on climate change, it's important to understand how the current scientific consensus on global warming evolved out of basic physical principles and a broad range of observations. In a lucid presentation designed for nonscientists, you will learn about:

  • The difference between climate and weather
  • The concept of energy balance, which governs the natural warming of the planet by the Sun and is the key to a stable climate
  • The greenhouse effect, which makes Earth warmer and more hospitable than it would otherwise be due to naturally occurring gases in the atmosphere, such as carbon dioxide and water vapor
  • The carbon cycle, which controls the rate at which carbon dioxide released by fossil-fuel combustion accumulates in the atmosphere, and how long it remains to enhance the natural greenhouse effect.

Along with these and other concepts, you will investigate the "fingerprints" of global climate change, ranging from borehole temperatures to melting glaciers to the altered behavior of plant and animal species. These and other indicators show that Earth has been warming at an unprecedented rate in recent decades.

You will also explore the physical mechanisms behind these changes and their connections to the increasing concentration of greenhouse gases in the atmosphere since the start of the Industrial Revolution. And you will look at the techniques for projecting future climates, along with the options for switching to alternative energy technologies to avoid the most disruptive scenarios that now seem possible.

Your Personal Scientific Briefing

Earth's Changing Climate addresses only scientific issues and makes no policy recommendations. Instead, this course is designed to serve as your personal scientific briefing to equip you to engage knowledgeably in one of the most important environmental issues of our time. In Lectures 1–6 you will focus on the scientific basis of climate; then in Lectures 7–12 you will come to understand the human role in climate change and explore projections of future climate.

Professor Richard Wolfson is no stranger to this subject. A physicist who has written and taught extensively about climate change, in 1996 he taped an earlier course for The Teaching Company titled, Energy and Climate: Science for Citizens in the Age of Global Warming. Professor Wolfson's new course is completely updated and represents the latest research and analysis in this fast-changing field.

A master at making difficult concepts understandable, Dr. Wolfson's other Teaching Company courses are Physics in Your Life, hailed by Library Journal as "a wonderful series of lectures that make learning physics fun and interesting," and Einstein's Relativity and the Quantum Revolution, which one listener said was "as exciting as a suspense thriller!"

In Earth's Changing Climate, Dr. Wolfson brings these educational gifts to bear on a subject that, at times, can be complex and controversial. You will find his presentation clear, objective, engaging, and illustrated with fascinating examples and analogies.

The Evidence Mounts

Like many scientific problems, the gradual assembly of a detailed picture of past, present, and future climates has involved creative detective work. For example, scientists traditionally test their theories by changing different variables, but this has not been possible with theories about climate change on Earth for two reasons: It's unwise to transform the planet just to see what will happen, and there are not multiple Earths to serve as test subjects.

However, researchers have identified cases where nature has done the experiments for us:

  • Mars: Mars's atmosphere has only about 1 percent the density of Earth's and provides a test for the theory of the greenhouse effect—in this case, for a planet with a thin atmosphere. As theory predicts, Mars has negligible greenhouse warming.
  • Venus: Venus's atmosphere has 100 times the density of Earth's and is about 96 percent carbon dioxide. Here, the greenhouse effect has struck with a vengeance—just as theory forecasts—driving temperatures to 500°C, hot enough to melt lead.
  • Mt. Pinatubo: The eruption of the volcano Mt. Pinatubo in 1991 poured massive amounts of dust into the upper atmosphere and allowed scientists to test their climate models. The fall in average global temperature over the following few years was in close agreement with what the models predicted.
  • Ice Cores: Deep ice cores from Greenland and Antarctica preserve a nearly million-year-old record of Earth's past temperature and atmospheric composition, showing a correlation between temperature and carbon dioxide concentration.

Using such clues, scientists are able to connect the 0.65°C rise in average global temperature since the start of the 20th century with the increase in atmospheric carbon dioxide over the same period. Looking ahead, they project a global temperature rise in the range of 1.5°C to 4.5°C during the 21st century, depending on the extent of worldwide economic growth and the rate of fossil fuel consumption.

An increase of a few degrees may not seem serious, but Professor Wolfson stresses that this is a global average. The rise will be more substantial in certain areas—particularly in the polar regions and over almost all land. He further notes that about 6°C separates the present-day climate from the depths of an ice age. Thus, an increase of a few degrees in global temperature is climatologically significant and may lead to many more extreme events, such as heat waves, intense precipitation, droughts, and intense tropical storms. At the same time, the sea level will be rising due to the thermal expansion of the oceans and the melting of land-based glaciers and ice sheets.

Over the longer term, a cause for worry is "surprise" events that could be initiated by as-yet poorly understood processes. These include the sudden slipping of a large land-based ice sheet into the sea with a resulting surge in sea level, or a major upset in patterns of ocean circulation.

As the evidence mounts, scientists will continue to refine their picture of what the climate is doing and where it is heading, and society will continue to grapple with this problem. You can begin to address it yourself—intelligently and prudently—by investing six stimulating and rewarding hours with this course.

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12 Lectures
  • 1
    Is Earth Warming?
    The course begins with a look at Earth's average temperature over the past century and a half, which shows an overall warming trend. How do scientists take Earth's temperature, and how do they interpret the pattern of variation? x
  • 2
    Butterflies, Glaciers, and Hurricanes
    This lecture looks at more subtle indicators of climate change and shows how statistical analysis reveals clear "fingerprints" of change on a host of natural systems. x
  • 3
    Ice Ages and Beyond
    Thermometer-based temperature rec­ords go back only 150 years. This lecture explores techniques that scientists use to push the global temperature record back millions, even billions of years. x
  • 4
    In the Greenhouse
    Stable climate entails a balance between incoming sunlight and outgoing infrared radiation. Infrared-absorbing greenhouse gases in a planet's atmosphere alter the details of this balance, causing the planet's surface to warm. x
  • 5
    A Tale of Three Planets
    How do we know that greenhouse gases such as water vapor and carbon dioxide are associated with the warming of Earth's surface? Nature provides a climate "experiment" on neighbor planets Venus and Mars. x
  • 6
    Global Recycling
    Cycling of materials plays a role in climate, with the most important cycles being those of water and carbon. Carbon added to the system stays for centuries to millennia and adds to the atmospheric carbon content, enhancing the greenhouse effect. x
  • 7
    The Human Factor
    Fossil fuel burning by humans has in­creased the concentration of carbon di­ox­ide in the atmosphere by nearly 40 per­cent since the start of the Industrial Revolution—to levels the planet has not seen in at least a million years. x
  • 8
    Computing the Future
    Climate models are mathematical descriptions, exploring how climate be­haves in response to human-induced changes and natural factors. Most models pro­ject a global temperature rise of several de­grees Celsius over the next century. x
  • 9
    Impacts of Climate Change
    A temperature rise of only a few degrees will have significant effects. The rise will be more substantial particularly in the polar regions and over almost all land. x
  • 10
    Energy and Climate
    Energy use is the dominant reason for our increasing influence on Earth's climate. Per capita energy consumption in the United States is more than 100 times our own bodies' energy output, meaning that we have the equivalent of about 100 "energy servants" each. x
  • 11
    Energy—Resources and Alternatives
    The fossil fuels that supply most of the world's energy have many deleterious environmental impacts, one of which is the emission of climate-changing greenhouse gases. This lecture surveys alternative energy resources. x
  • 12
    Sustainable Futures?
    Avoiding disruptive climate change in the future probably means keeping atmospheric carbon dioxide to at most a doubling of its preindustrial level. This final lecture discusses several possible paths to a stable climate. x

Lecture Titles

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Richard Wolfson
Ph.D. Richard Wolfson
Middlebury College

Dr. Richard Wolfson is the Benjamin F. Wissler Professor of Physics at Middlebury College, where he also teaches Climate Change in Middlebury's Environmental Studies Program. He completed his undergraduate work at MIT and Swarthmore College, graduating from Swarthmore with a double major in Physics and Philosophy. He holds a master's degree in Environmental Studies from the University of Michigan and a Ph.D. in Physics from Dartmouth.

Professor Wolfson's published work encompasses diverse fields such as medical physics, plasma physics, solar energy engineering, electronic circuit design, observational astronomy, theoretical astrophysics, nuclear issues, and climate change. His current research involves the eruptive behavior of the sun's outer atmosphere, or corona, as well as terrestrial climate change and the sun–Earth connection.

Professor Wolfson is the author of several books, including the college textbooks Physics for Scientists and Engineers, Essential University Physics,and Energy, Environment, and Climate. He is also an interpreter of science for the nonspecialist, a contributor to Scientific American, and author of the books Nuclear Choices: A Citizen's Guide to Nuclear Technology and Simply Einstein: Relativity Demystified.

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Reviews

Rated 4.3 out of 5 by 52 reviewers.
Rated 3 out of 5 by A Little Too Basic This review has to be considered relative to one's background. As with all science and math classes offered through the Great Courses, what is learned depends a lot on how much you already know. That makes it hard to assign stars. If you don't learn much because you have an extensive background in a subject, that doesn't make an introductory course poor. Right? I give this course 3 stars because it could be better. It is meant to be an introduction, but I found it too basic and repetitive. It's a sort of "Time" magazine type of approach. Regardless of your interest in the subject, you've probably heard most of this already. Knowing what a person 'believes' about climate change will probably influence the review. I happen to agree with the science that states a) the earth is warming and b) man is greatly contributing to the warming. From that you may conclude that I have no disagreement with content. I did hope to learn some more science. Solar influence is scantily covered though the sun does seem to be in a peculiar phase and has been throughout the most severe of the climb in global temperature. No, solar output is not to blame. But there are things happening with the sun that should have been covered. I would have liked to have more content on how different aerosols impact climate change such as volcanic ash and large fires. Science is also discovering man made chemicals in the atmosphere that are far worse than carbon. Also, there are time references which are confusing and sometimes seem to conflict with the general thesis that man is causing temperature rise. So, we had a mini ice-age in the 1600s and then things warmed up. And we had an odd dip in the late 70's. Ah, but we haven't seen this much carbon in the atmosphere in 250,000 years! It just gets a little jumbled. Dr. Wolfson's "Physics in Your Life" course is one of the best offered through the Great Courses. This isn't one of the best. I recommend the course if you are totally new to the subject of climate change. I do not recommend the course if you have a basic understanding of the subject. December 21, 2013
Rated 5 out of 5 by Where's the Evidence Wow - I had no idea of the vast array of evidence and how all these data points line up so well. Very informative. Our national news agencies and the once that claim to be need to take this course. July 8, 2013
Rated 5 out of 5 by Excellent Overview Grounded in Science The professor does a great job of covering the basic facts, theories, evidence, models related to global warming. The fundamental science still holds up well and is important for a reasoned debate, even as there have been new findings about details since the course was made. He concentrates on the science, describes the evidence for and against claims that he reviews, and for the most part stays out of the policy arena (other than to discuss some of the proposed policy responses at the end) This science fundamental approach is especially useful since there has been so much FUD, (fear, uncertainty and doubt) spread around in this debate -- especially but not solely by those who prefer to ignore the issue. We'd all be better off, if people first understand the basic science at least to the level described in this course before beginning to discuss the issue. Great job, Professor Wolfson June 16, 2013
Rated 3 out of 5 by Climate change--what's that? If you know nothing about climate change this is the course for you. As others have said, this course is very outdated. This is truly a course for the beginner. Professor Wolfson is a good presented, but his information is sorely lacking and requires updating to be of value. If you buy this, buy the DVD due to the graphs and climate models. April 15, 2013
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