The year without a summer

Most of us know the origin of Frankenstein as a piece of literary gossip. In June 1816, a group of English writers staying by Lake Geneva were kept indoors by endless storms, and Lord Byron suggested that each of them write a ghost story. One of the guests, the eighteen-year-old Mary Godwin, later Mary Shelley, began the tale that became Frankenstein. It is one of the most retold anecdotes in English literature. In Tambora: The Eruption That Changed the World, the literary scholar Gillen D'Arcy Wood asks the question that the gossip skips over. Why was the weather so bad?

The answer lies on the other side of the world. In April 1815, Mount Tambora, on the Indonesian island of Sumbawa, erupted with a force unmatched in recorded history. The explosions were reportedly heard more than 2,000 kilometres away, and the blast, the ash and the famine that followed killed tens of thousands of people in the region. The eruption also threw vast amounts of sulphur high into the atmosphere, where it formed a thin veil that reflected sunlight back into space. The following year, Europe and North America lived through what became known as "the year without a summer".

Wood is at his best when he follows that veil around the globe. Snow fell in New England in June, frosts destroyed crops in the north-eastern United States, and cold rain ruined harvests across much of Europe. Food prices soared, and in Switzerland hungry families took to the roads to beg. In south-west China, failed rice harvests led to famine. In New England, thousands of farming families gave up and moved west, part of a migration that helped to settle the Midwest. Wood also connects the disrupted Indian monsoon with a deadly cholera outbreak that began in Bengal in 1817, a link that is, by its nature, harder to prove.

The book is not always easy going. Wood moves quickly between continents, and readers who want a single, steady narrative may find the jumps disorienting. The chain of cause and effect is occasionally stretched thin, too. Yet the cumulative effect is powerful. By the time the book returns to Lake Geneva, the gloomy summer of Frankenstein no longer looks like a picturesque backdrop. It looks like one corner of a global emergency that most of its victims never understood.

The relevance to our own time is hard to miss. Scientists can now track volcanic clouds by satellite and forecast their effects on the weather. Whether today's food systems could absorb a shock of that size is a different matter, and the book makes uncomfortable reading on that point. For anyone who knows 1816 only as the summer Frankenstein was written, it is a demanding but rewarding corrective.