It also worth mentioning that Kahn and the Hudson Institute, as well as other think tanks past and present, were reacting to the enormous impact of Limits to Growth, one of the first attempts to use models and computers to try to track past trends and future possibilities. The Club of Rome, which was associated with these exercises, was perfectly respectable and headed by Fiat’s chief, Aurelio Peccei (1908-84). Nonetheless, plenty of conservative doubters attacked the Club and Limits, carefully picking out one or two of their scenarios to ridicule while ignoring the rest. Paul Ehrlich told me he had the same experience with The Population Bomb, which also offered scenarios rather than cast-iron predictions. Kahn was not so unprofessional as to commit the same egregious error.

As for all four types melding into one-it is no longer wishful thinking. I took the trouble to call the heroine in my novel, 2007: A true story waiting to happen, Kate Schumpeter. For me she symbolised the way Kahn’s categories would have to merge this century if we are to survive. Kate is an innovator and an entrepreneur. She eventually becomes green as well. But there is not a scintilla of Malthusian gloom about her. You get the gist from the following cameo of Kate’s namesake-the great economist Joseph Schumpeter-given by Queensland University ’s Professor Mark Dodgson in January 2006 on ABC Radio National’s Ockham’s Razor.

Joseph Schumpeter was one of the most important economists of the twentieth century. In a world where technology and innovation are so important for us all, he was one of the first to examine their impact on the economy. He was quite a character. He was Austrian Finance Minister, a Harvard professor, and always proclaimed to have three rather immodest ambitions: to be the best economist in the world, the most skilful horseman in Austria, and the greatest lover in Vienna. On his deathbed, he glumly accepted that there was probably one person who’d always been better on a horse…

Schumpeter used wonderfully colourful and evocative language. He argued that innovation unleashed ‘the gales of creative destruction’. It arrives in great storms of revolutionary technologies like steam power and computers that fundamentally change and improve the economy. Innovation is creative and beneficial, bringing new industries, wealth and employment, and at the same time is destructive of some established firms, many products and jobs and the dreams of failed entrepreneurs. For Schumpeter, innovation offers the ‘carrot of spectacular reward or the stick of destitution’.

This eruption of a new kind of innovation is happening already. Amory and Hunter Lovins, of the Rocky Mountain Institute, have written Natural Capitalism, containing enough ideas to help us tackle the next 50 years. Dave Suzuki has covered similar ground in Good News for a Change. In London, the Forum for the Future, chaired by Jonathon Porritt, has a magazine called Green Futures, in which these ideas have been promoted for over ten years. It invites corporations to submit a £5000 joining fee and a statement about how they are, as organisations, facing the future. Promotion puffs written in the customary corporate way are unacceptable and immediately returned to sender. Only realistic grapplings with possibilities, good or bad, are accepted. Then there is the comprehensive The Natural Advantage of Nations, Business Opportunities, Innovation and Governance in the 21st Century, edited by Karlson Hargroves and Michael Smith, two Australians from the Natural Edge Project. Gradually business is learning that being green is a supremely serious venture, and profitable. Environment Business Australia is taking its own approach, successfully. It suggests that green enterprise in Oz will be worth $40-50 billion a year by 2010.

What Kahn did not foresee 30 years ago, I repeat, is that his four distinct types would soon morph into one on today’s world stage. The Australian Business Round Table was launched in 2006 by six magnificent CEOs (whose companies included Westpac, Visy Industries, I AG, Swiss Re, Origin Energy and BHP). Put them together with leaders such as Lord Oxburgh and Cathy Zoi (who now runs Al Gore’s office but promises to return to Australia) and you have the beginnings of lift-off.

I was born in January 1944. Hitler was still going strong. The atomic bomb had not yet been tested, nor dropped on two Japanese cities. Martha Gellhorn was yet to write about the hitherto unsuspected (by the public at least) outrage of the concentration camps. I arrived in a world not dissimilar to hell. So I know, as you do, how bad things can get. We also know how good they can be, some of us.

Today, like Tolstoy’s unhappy families, our bad things are bad in different ways. This is how our problem is posed by Martin Rees:

We are entering an era when a single person can, by one clandestine act, cause millions of deaths or render a city uninhabitable for years, and when a malfunction in cyberspace can cause havoc worldwide to a significant segment of the economy: air transport, power generation, or the financial system. Indeed disaster could be caused by someone who is merely incompetent rather than malign.

Martin Rees is a calm, immensely courteous Welshman. He is the last person on Earth to be inclined to histrionics. He is also one of the most distinguished scientists alive, combining, somehow, the positions of President of the Royal Society of London, Master of Trinity College, Cambridge, member of the House of Lords and professor of astrophysics (he had to give up being Astronomer Royal!). Yet this sensible man was willing to have a wager on oblivion. In his book Our Final Century (note, no question mark!), he wrote:

I staked one thousand dollars on a bet: ‘That by the year 2020 an instance of bioerror or bioterror will have killed a million people.’

Of course, I fervently hope to lose this bet. But I honestly do not expect to. This forecast involved looking less than twenty years ahead. I believe the risk would be high even if there were a ‘freeze’ on new developments, and the potential perpetrators of such outrages or mega errors had continuing access only to present-day techniques. But of course, no subject is forging ahead faster than biotechnology, and its advances will intensify the risks and enhance their variety.

To Lord Rees’s nightmare add mad mullahs, myopically dim US presidents and a few million folk waiting and even wishing for Armageddon, and you have a mixture that even my contemporaries in 1944 might have found too dreadful to contemplate. At least back then you had some almost Utopian optimism about possible futures. One monster, Hitler, was about to be vanquished; another, Stalin, would last but another nine years. Little did we imagine that the end of the world would come, not through the agency of the Devil but by the actions of idiots. To misquote T.S. Eliot: ‘This is the way the world ends, not with a bang but a blunder.’ The whimper comes afterwards.

In his book Last and First Men, published in 1930, Olaf Stapledon wrote a two-billion-year history of the human race. In his tale we grow wings and take to the sky and move from Earth to the outer reaches of our solar system-though we do not leave it. Stapledon was a philosopher trained, like Richard Dawkins, at Balliol College in Oxford, though he later went west to the University of Liverpool to lecture. His narrative is not enlivened by winsome or wicked characters or personal vignettes, but proceeds, almost like a formal history, to leap through the centuries and millennia. He was boldly optimistic that we have many millions of years ahead of us, even though we have managed only about 120,000 so far as modern humans and barely ten thousand years of civilisation.