Horizon Season 2001 Episode 5 Snowball Earth

In Horizon season 2001 episode 5, titled "Snowball Earth," the viewer is taken on a journey through the history of our planet's climate. The show delves into the theories of geological cycles that have affected the planet over millions of years, in particular, the "snowball Earth" event that is believed to have occurred 600 million years ago.

The show begins with a brief explanation of the concept of the greenhouse effect and how it regulates our planet's temperature. This lays the foundation for the explanation of how "snowball Earth" occurred. The episode discusses the idea of solar radiation and the role it plays in Earth's climate. The sun is the main source of energy that drives our planet's climate and weather. In the past, however, the Earth's orbit around the sun was not always the same. There have been times when the distance between the Earth and the sun has been greater, or the angle at which the Earth spins has changed. These minor changes can have a significant impact on our planet's climate.

The episode discusses how the Earth went through a period of intense glaciation, where the planet's temperature plummeted, and ice sheets covered the entire planet. The viewer is taken to locations around the world where evidence of this glaciation can be seen in the geological record. The episode also looks at the chemical makeup of the rocks and sediments that have been preserved from this period and how they can be used to reconstruct the climate of the past.

The show explains how scientists have come to the conclusion that the snowball Earth event was caused by a positive feedback cycle. It is thought that a small decrease in temperature caused the ice to form, which then reflected more solar radiation, causing the planet to cool even further. This positive feedback loop continued until the entire planet was covered in ice. The critical factor in allowing the planet to recover from this event was the presence of volcanic activity, which released greenhouse gases into the atmosphere, allowing the planet to warm up once again.

The show explains that there have been more recent glaciation events, such as the Ice Age, which ended around 11,700 years ago. The viewer is taken to locations where evidence of this event can still be seen today, such as the massive glacial erratics that litter the landscape of northern Europe.

The episode concludes by discussing the implications of climate change and how it could affect our planet in the future. It is suggested that increased CO2 levels caused by human activity could lead to a similar positive feedback loop, leading to a "runaway greenhouse" effect. This would result in a planet that is too hot to sustain life. The show emphasizes the need for action to prevent such an event from occurring.

Overall, Horizon season 2001 episode 5, "Snowball Earth," offers a fascinating exploration of our planet's climate. A mixture of beautiful cinematography and detailed explanations of geological and scientific processes make for a compelling and informative viewing experience. The episode's message is clear - the drastic changes in our planet's climate have occurred before and could happen again if we do not take care of our planet.