Climate change, could it happen The Day After Tomorrow?

In 1999, a snippet of news that should have stopped the world in its tracks caught my eye. Two South Pacific islands had disappeared under the sea. Many more were at risk. For decades, the islanders had been trying to alert the world to the rising ocean. Now they were moving entire villages inland, hut by hut. Mass evacuation loomed. But where to? Stuck in a corner of a newspaper, the islanders' plea to the world hit a wall of disinterest.

Then, the scenario of a drowning world seemed a far-fetched fantasy. I did some research on global warming and what I found out made my heart stop. The stories that spark my imagination are about individuals on the edge, on the cusp of change. The plight of the islanders began to haunt my imagination. Sometimes you don't choose the stories; they choose you.

And so I came to write Exodus and its sequel Zenith, the future story of a drowned earth.

Now global warming is on every front page. Evacuation plans for the Pacific Islanders are tied up in red tape. No one wants the world's first climate change refugees.

By 2100, the year of my future story, global warming is forecast to destroy the lives of over 100 million people and create the greatest refugee crisis the world has ever known.

It's all too much, too terrible, to take in. Especially if you're young and your life lies ahead. It's your future at stake. Best just plug in the iPod, have a laugh on YouTube and hope the grown-ups sort it out in time.

And yet ... the response from young readers to Exodus and Zenith has been astonishing. Fed a curriculum that's so out of date on global warming it's (almost) laughable, many teenagers have harnessed the facts for themselves. But thousands of emails I've been sent say that stepping into the story of a devastated future and living that reality through characters they've grown close to has made them really understand - and want to act.

That's the great power of fiction. As a teenager I devoured challenging, speculative fiction that asked big, hard questions about the world. Back then, there was little fiction written specially for young adults, so I leapt from Alan Garner and Ursula Le Guin's fantasies to science fiction like Le Guin's The Left Hand of Darkness and John Wyndham (the melting ice caps in The Kraken Wakes now seem eerily prescient). Books like these forged my imagination. They were prisms through which you could explore the issues and apocalyptic terrors of the time.

With such a precarious future looming you would expect today's writers - especially those who engage the imaginations of the young - to seize the gauntlet. Young adult fiction is now a feisty scene. There's plenty of fine writing, fantasy galore and some sci-fi (mostly a dramatic backdrop for a regular teen fictionscape of family, feelings and friends - and nothing wrong in that). But why so little fiction that takes on the really big questions that frighten and fascinate the 21st-century generation?

Humanity has a rendezvous with destiny. As President Jacques Chirac said, our house is burning down. Our future depends on us turning a new page in the human epic and imagining a whole new way of being in the world. Science is key, but fiction can offer a map, torch and compass through terrors and dreams.