By 2109 the centenarians born this year could be enjoying their twilight years in high-tech mega cities, flying around in robot-operated sky cars while chatting on their (hands-free) hologram "telephones" to their great grandchildren.

Thanks to anti-ageing tablets, some futurologists predict, the centenarians may have retained their relatively youthful looks and be able to look forward to their holidays playing cybergolf in the biodomes of the moon's best hotels.

There are, though, much darker visions of the future in which, many serious scientists fear, the 100-year-olds of 2109 could be fully reaping the damage from mankind's crimes against the environment. They could find themselves living in a hot, crowded, frightening world, with the ancient wars of religion and oil long forgotten and replaced by horrific global conflicts as an increasingly large number of humans compete for diminishing stocks of drinkable water and tillable land.

Last month Richard Betts, head of climate impacts at the Met Office, delivered the most devastating weather forecast ever given by a meteorologist: 4C of global warming by the end of the century, much higher temperature rises in some regions, including 15.2C in the Arctic and 10C in much of Africa, rainfall down by 20% in many areas, leading to drought and famine, but higher up in other regions, such as parts of India, triggering disastrous floods. There may also be a frighteningly high number of humans competing for the fast-receding resources. When the centenarians were born, the world's population was estimated by the US Census Bureau at almost 6.8 billion. Growing, according to the UN, at the rate of 203,800 people a day, it will have topped 9.2 billion by 2050.

This year scientists at the Australian Museum looked as far ahead as they dared, and the museum's website turned its predictions into mock television news bulletins, The News from the Future.

It did not make cheerful viewing as the impassive newsreader told of riots as the pump price for water rose yet again, outraged public demands for an immediate stop to the export of tanker-loads of drinking water, and the harsh reception for migrants whose leaders bought land from the Australian government to replace their original homes now under the waters of the Pacific.

So the citizens of 2109 may be looking for as much consolation as they can from their artificially-grown food, textured and flavoured to dimly recall the joys of long vanished delights such as cod. Some of the strains of modern life may be taken up by robots which do all the housework.

There might also be the option – it has long been predicted – of some "electro sex", which might work by directly stimulating that part of the brain which would otherwise need to be engaged by messy old fashioned human contact.

They would still need to play safe, though, as author Richard Kadrey recently warned in the future-gazing British magazine Wired: "There might be some really interesting side-effects [of electro sex], like people simply burning out sectors of their brain."