We are doing an uncontrolled experiment with the climate of the only planet we have.

It took the Earth and the Sun hundreds of millions of years to produce the world's petroleum — in 150 years we've used up nearly half of it. With worldwide oil consumption rapidly expanding, we are already burning up 25 billion barrels a year. We will soon start to run out of oil.

With any natural resource, the amount available starts at zero when it's first discovered, rises to a maximum that will never be exceeded, and then declines forever. As the demand for oil only goes on increasing, we will be in trouble when we reach the maximum, not when we pump the last barrel of oil out of the ground. That should occur (by symmetry) roughly when we reach the halfway point in our use of the stuff. We are already very close to the halfway point.

Of course, all fossil fuels are replaceable. Natural gas could replace oil, but the worldwide peak for natural gas is only a decade or two behind the oil peak, so that's a temporary solution at best. Other possible substitutes for oil include shale oil, methane hydrate and coal: all of these have very serious drawbacks. Another possibility is biofuels, such as ethanol or biodiesel, but it's far from obvious that their use could be scaled up sufficiently to replace oil. And whatever does replace oil will probably continue to pour greenhouse gases into the atmosphere. We are doing an uncontrolled experiment with the climate of the only planet we have. It is very foolish indeed.

What is desperately needed is a crash programme to enable us to kick the fossil-fuel habit now, before we use all the stuff up. The fact is, we are very good at solving technical problems once we put our minds and resources on the line. But we need courageous, visionary political leadership that will challenge us scientists to do it — just as JFK once challenged us to put a man on the Moon. Unfortunately, that seems unlikely. But the alternative is nothing less than the end of our oil-based civilization.