This is a remarkable and timely book by a scientist who is well known internationally both for her research on climate and for her innovations in education. In straightforward and accessible language, Catherine Gautier introduces the reader to a complex variety of interlinked issues. The theme that unifies this book is that the seemingly disparate topics of oil, water, climate, and population are in fact inexorably bound together by powerful interconnections. As a result, at the dawn of the 21st century, humanity is confronted with a set of urgent challenges. It is no exaggeration to say that these challenges put the very future of civilization at risk.

It is paradoxical that these challenges should arrive at a time when the human race has made remarkable strides in overcoming long-standing obstacles. For millennia, humanity struggled to maintain population growth in the face of the ancient threats of starvation, disease, and war. Recent decades, however, have seen an explosion in human numbers and, in some countries, extraordinary increases in prosperity.

Two thousand years ago, the entire earth supported a population of only about 300 million people. It took until about 1800 for global population to pass 1 billion, and the doubling of that figure to reach 2 billion was not achieved until around 1930. In retrospect, we can now see that, at about that time, a dramatic population surge began to occur, and the global population rose to about 6.5 billion people by 2006.