From Out of Gas, by David L. Goodstein, 2004:

There is no existing technology capable of replacing the oil we will soon be without, nor is there any on the horizon that we can depend on to replace the remaining fossil fuels when they are exhausted. ...

... Civilization as we know it will come to an end sometime in this century unless we can find a way to live without fossil fuels.

David L. Goodstein is a U.S. physicist and educator. Since 1988, he has served as Vice-provost of the California Institute of Technology (Caltech), where he is also a professor of physics and applied physics.

David L. Goodstein:

So, what does the future hold? Well, for one thing, there will be an oil crisis very soon. Whether that means it has already begun or won't happen until later in this decade or sometime in the next decade, I don't know. In my view, the numbers are not dependable enough for us to say. However, while the difference between those estimates may be very important to us, it’s of no importance at all on the time scale of human history. Either we, our children, or perhaps our grandchildren, are in for some very, very bad times.
From a talk given by David Goodstein at Caltech in April 2004, quoted in the New York Times review of his book "Out of gas". See http://arral.org/news/wow/saved_6507.html

David L. Goodstein is a U.S. physicist and educator. Since 1988, he has served as Vice-provost of the California Institute of Technology (Caltech), where he is also a professor of physics and applied physics.

Paul Krugman

So what should we be doing? Here's a hint: We can neither drill nor conquer our way out of the problem. Whatever we do, oil prices are going up. What we have to do is adapt.

The Oil Crunch, by Paul Krugman, The New York Times, May 7, 2004

Colin Campbell

Crude Awakening: Preparing Ottawa-Gatineau for Peak Oil