In the future there are likely to be dramatic changes in the world's climate. Whole populations may have to move as their land becomes uninhabitable. This seems hard to believe, but it has happened before.
Three thousand years ago, the population of the Scottish Highlands abandoned their land because the climate changed. The discovery of why this happened, and how, suggests that the earth's atmosphere may be far more unstable than is realised. The evidence comes from Nordic sagas, Irish oak trees, the poetry of Byron and the history of volcanic eruptions. Combined with satellite observations and computer models of the world's climate, they show that a time of darkness across the globe is a real possibility.

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