How fossil fuels are made, and a comparison of how long it takes to store energy in coal, oil and natural gas (millions of years), with how fast we’re using them (hundreds of years.)

Studying ice cores at the National Ice Core Lab, Alley shows how ancient ice contains records of Earth’s past climate. Over 400,000 years, and even longer, levels of carbon dioxide have risen and fallen from about 180 parts per million to 280, varying from colder in the Ice Ages to warmer in interglacial periods. Today, however, for the first time in more than 400,000 years, CO2 is at 390 parts per million and continuing to rise at 2 parts per million (ppm) per year. Alley relates the onset of this change to the Industrial Revolution.

In 2010, for the first time, the Pentagon focused on climate change as a significant factor in its Quadrennial Defense Review of potential risks and strategic responses. Rear Admiral David Titley, Oceanographer of the Navy, explains why the US military sees clear evidence of climate change, and how those changes will affect future military and humanitarian missions. (See also the full transcript of his Interview.) Of particular note is the likely impact of sea level rise on naval facilities which are, of course, primarily on coasts. Titley argues that earth and physical science offer useful projections of future climate that we can use to make sound decisions.

Just how much energy can Sun, hydropower, biomass and geothermal offer? This segment sets a target of seeing whether, in principle, renewable energy resources could meet today’s global energy needs of about 15.7 terawatts, described by Richard and illustrated on camera as the equivalent of 157 billion 100 watt light bulbs. Starting in the deserts of America’s Southwest, one of the sunniest places in the world, we travel to Spain, Brazil and New Zealand putting numbers on the potential of some of the most promising, non-CO2 emitting renewables: solar, hydro-power, biomass and geothermal.
The pros and cons of each energy source are cited, and the Annotated Script provides several links to find out more. Richard points out that today’s technologies have begun the long process of harvesting this vast renewable potential in ways that are already—or soon will be—economical and technologically adequate. Looking at a giant Concentrated Solar Thermal plant in Spain, soon able to supply the entire power needs of the nearby city of Seville, and the long transmission lines taking power from the huge Itaipu Dam to one of Brazil’s largest cities, he says we’ve already made a start.