Early in the piece, an elderly Jane Seymour hands Reeve an old pocket watch, which he carries when he travels backwards in time and, in turn, gives to a younger Seymour. This creates a causal loop – the watch is never built and never ‘ends’ – one of the paradoxes cited as proof that time travel is impossible and, worse, possibly a plot flaw.

Thirty years later, the risks of causal loops were at the forefront of my mind while I was developing a time travel trilogy for young adults. It wasn’t just important to me that the story was authentic in terms of character journey, it also had to be solid in terms of social structures and the ‘rules’ of this fictional world.

For a start, I’d read enough scientific journals to know that time travel forwards is possible, at least in a relative sense, so I carried that kernel of truth into the year 2084 when three teenagers discover a skill that lies dormant in all humans. By practising a mediation technique, they learn how to re-locate themselves in time.

The catch: they are only able to jump forwards, not back.

My husband and I lived in Footscray before moving our young family to regional Victoria in 2004, so I already knew the shock of returning to a familiar place only to find buildings sprung up overnight or children grown tall in the blink of an eye. Without actually naming Melbourne, I set key events in Footscray Park, Swanston ‘Boulevard’, the State Library. Even the experience of ‘time jumping’ was inspired by a common everyday occurrence: sleep.

In effect, I picked up the solid line that is the world around me, and carried the dots into a fictional future.

As a nod to the brain-melting fun of causal loops, I decided that information could indeed travel backwards. Physical objects may be governed by time’s arrow, but truth is eternal.

From this idea sprung a future where everyone is microchipped: infinitely useful as a storytelling device, since characters are able to see events from the past on ‘the grid’. In terms of future-building, a whole social structure blossomed from those microchips – food shortages have led to a ration system; chipped citizens are able to access food, education and technology, while unchipped illegals struggle to survive.

Clearly, I was also writing a future affected by climate change, even though I’d never set out to do so. But this new development also provided me with best antagonist I’ve ever had the privilege to write – neither good nor evil, but intrinsic to our survival: the natural environment.

The first two books in the trilogy deal with storms, a blackout, drought, food security and water shortages, as well as two versions of a bushfire (it’s a time travel story set in Victoria, after all). By the time I’d begun to develop the final instalment, images of Swanston St flooded by seawater began to play in my imagination. I kept seeing the Flinders St clock tower above the peaks of waves. The opening scenes even saw characters hiding in massive water-stained drains.

My problem was, none of the scientific predictions see those images as remotely likely. Even when following the ‘high end scenario’ shown on the Australian Government’s ‘Geoscience Australia’ website, sea levels in the year 2100 might reach 110 cm – the banks of the Yarra River will get a bit wider, but few nearby properties are under threat.

Contrast this with ‘The 100 Metre Line’ blog, which shows impacts of sea levels rising 80 m – the whole Melbourne CBD is under water, Port Phillip Bay extends as far north as Hurstbridge. It’s a confronting sight. At least, it would be if it were an accurate prediction.

The reality of sea level rise is that while low-lying islands face genuine threat, most city encroachment is expected to occur gradually enough for us to respond, but search google images with ‘sea level rise city’, and you’ll find artists’ impressions of skyscrapers rising above blue seas: images that have sprung from a collective fear of the impacts of climate change. They’re not reflections of present-day science, but the present-day zeitgeist.

When I think back to our childhood fascination with the pocket watch, it wasn’t about scientific inauthenticity or plot flaws, it was because the watch helped us see the world in new ways. It made us shiver with possibility: what if that were real …

So I allowed the story to guide me. I was, after all, writing fiction so I was free to push beyond the boundaries.

I’m glad I did. Once our city has been submerged, our fictional future doesn’t face complete environmental breakdown, but instead emerges into images of regeneration. Even the social structures shift; characters who once wielded power are now forced to work with others in order to survive. From my fears of death and destruction have come signs of hope, resilience and renewal.

The story may not be as scientifically accurate as I’d hoped, but that’s okay. I realise now that it wasn’t a scientific truth I was exploring, but an emotional one.

I’m looking forward hearing how readers of the first two books respond to the final instalment – one in particular, my sister.