TTC Video - Earth's Changing Climate [repost]

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.

Lectures:

01–Is Earth Warming?
02–Butterflies, Glaciers, and Hurricanes
03–Ice Ages and Beyond
04–In the Greenhouse
05–A Tale of Three Planets
06–Global Recycling
07–The Human Factor
08–Computing the Future
09–Impacts of Climate Change
10–Energy and Climate
11–Energy—Resources and Alternatives
12–Sustainable Futures?