4. The enemy within

‘The Enemy Within’ begins with volcanic super-eruptions and their devastating consequences such as the 1815 eruption of volcano Tambora in Indonesia, and ancient eruptions in Yellowstone, USA, and Toba, northern Sumatra. Volcanic explositivity index, eruption magnitude, and eruption intensity are explained. Volcanic landslides in Hawaii and the Canary Islands will, in the future, result in giant tsunamis wreaking havoc around the Pacific and Atlantic Ocean rims. But when will they happen? Finally, the fate of industrial cities, such as Tokyo, located near active fault-lines and in earthquake zone, and the resultant effects on the world economy are considered.

5. The threat from space

‘The Threat from Space’ considers the threat of asteroids and comets colliding with Earth. Potential impacts of Near Earth Asteroids, with almost circular orbits, have been identified, but the threat from comets, which follow strongly elliptical paths, is uncertain. The Mexican asteroid impact 65 million years ago is thought to have wiped out two-thirds of all species living at the time. The Earth will be hit again at some point in the future, but how will it affect us? This will depend upon three things: the size of the object, how quickly it is travelling, and whether it hits the land or the ocean.

2. Global warming

‘Global warming’ explains that the Earth is now warmer than it has been for over 90 per cent of its 4.6 billion year history and is heating up faster than at any time in the last 11,500 years. In 2013, atmospheric concentrations of carbon dioxide exceeded 400ppm, the highest level for at least 15 million years. The 2013 IPCC 5th Assessment Report forecasts that global average temperatures could be 5°C higher and sea levels 1m higher by 2100. No one can escape the effects of anthropogenic climate change, but unless there is a widespread adoption of sustainable development, urgent action to seriously tackle climate change may only happen if there is an Earth-shattering climate catastrophe that no one can ignore.

Epilogue

‘The Epilogue’ summarizes our current position. We are well into a cycle of warming that is certain to lead to dramatic geophysical, social, and economic changes during the next hundred years that will impinge detrimentally on everyone. At the same time our planet is teetering on the edge of the next Ice Age. Asteroid impacts, giant tsunamis, or volcanic super-eruptions cannot fail to result in millions of deaths and the enormous disruption of our so-called advanced global society. It concludes that—major comet or asteroid impact aside—it is unlikely that all human beings will be wiped out in the foreseeable future.

3. The Ice Age cometh

What turns ice ages on and off? ‘The Ice Age cometh’ considers the potential impact global warming may have on the arrival of the next expected Ice Age. Will global warming fend it off or will it accelerate the onset of the next big freeze? Conditions on Earth during the great freezes of the Cryogenian and the most recent Quaternary ice ages are described and what triggers them considered, including the Croll–Milankovitch astronomical theory. The Little Ice Age (c.ad 1450–1850) and the Medieval Warm Period (c.ad 1000–1300) are discussed along with the role ocean circulation (especially the Atlantic Meridional Overturning Circulation) has to play.

1. Planet Earth

Earth is the most dynamic planet in our solar system, but the very same geophysical features that make our world so life-giving and life-preserving also make it dangerous. ‘Planet Earth: in a nutshell’ provides a potted biography of the Earth’s 4.6 billion years of history describing the major natural hazards—storms, floods, earthquakes, volcanic eruptions, landslides, and asteroid and comet collisions—that have assaulted our planet. Floods constitute the greatest of all natural hazards—at least 100 million people a year are affected—and this situation is likely to continue given a future of rising sea levels and more extreme precipitation.