All our lives in the year 2020 could be startlingly different from today, the UK's Environment Agency believes.
Wind power is one source of sustainable energy
Using a fictional family called the Dumills, the agency describes a Britain where solar power dominates and every loo has a robot to analyse excrement.
We can look forward to cleaner air, better public transport and an end to infuriating traffic jams, it suggests.
The portrait of Britain's future is being debated at the Environment 2003 conference held in London this week.
The attempt at futurology on the part of the Environment Agency (EA) is intended to make people think about where we might be headed if certain polices are adopted - or not.
The agency has invented a family called the Dumills, who live in South East England in the year 2020, to make its point.
EA VISION - LIFE IN 2020
High oil prices mean imported foods are no longer affordable - local produce dominates
A household windmill and solar panels generate surplus electricity which is pumped back to the grid, earning the family money
Homes have their own purification plants
The Dumills inhabit a world that is in some ways "less modern" - many homes grow their own food because, thanks to soaring oil prices, imported food is too expensive.
In other ways, however, the Dumills' existence is truly futuristic, with all human excrement being automatically analysed by a robot in the loo.
Many children are adopted, including the Dumills' daughter Britney. Plummeting sperm counts have made natural conception very difficult.
And most workers are immigrants because global warming has rendered large swathes of the world uninhabitable.
The Dumills, who do not have a genetic predisposition to disease, are the lucky ones.
But fictional neighbour Marjorie is one of the unfortunates whose genetic predisposition to a variety of future illnesses means that to qualify for insurance or a mortgage, she has to live in a sterile equivalent of a bubble.
EA VISION - LIFE IN 2020
Toilets automatically analyse samples of family excretions, and digitally send the information to a computer at the doctor's surgery
A domestic greenhouse gas allowance is debited automatically from a smartcard
Much of the world is uninhabitable - the West Coast of Ireland is under water, much of central Africa has turned into desert
But the agency's portrait of life in 2020 is not entirely negative. The air is cleaner, public transport is better and - thanks to successful congestion charges - traffic jams are a thing of the past.
Environmentalists and MPs have gathered for the Environment 2003 conference, co-hosted by the EA, to discuss how Britain might build a more sustainable future.
Speakers were to include the Environment Secretary Margaret Beckett and Tony Juniper, the head of Friends of the Earth.
Margaret Beckett and Tony Juniper warn that global warming might force millions of people to move across the world because of flooding and droughts.
Along with the international development minister, Hilary Benn, Ms Beckett has commissioned a new report on water and sanitation.
A taskforce has also been set up to push Britain towards a more sustainable future. The initiative will encourage every household to have its own water purification and recycling unit.
But gadgets and technical fixes are only part of the answer, and a cultural shift in society is needed, according to Barbara Young, the Environment Agency's chief executive.
The use of resources like power, water and wood needs to be strictly monitored - and restricted.
However, not everyone believes such dramatic measures are really necessary.
Prominent global warming sceptic Philip Stott believes the Environment Agency's vision of the future is alarmist and, he argues, not supported by science.
"These scenarios are, in one sense, 'utopian', in that they are about worlds that are unlikely to exist anywhere (even in Tunbridge Wells), while they stem from a dystopian premise that everything about the modern age is gloom and doom," said Stott, Professor Emeritus, University of London.
"Like Eeyore, the EA should be left to ruminate in a boggy place, while the rest of us enjoy our lives and continue to develop without being lectured to by these worryworts."