The renowned physicist muses on the days when the Sahara was wet.

Randall Hagadorn, Courtesy of the Institute for Advanced Study

The mystery of the wet Sahara has fascinated me ever since I read Henri Lhote’s book, The Search for the Tassili Frescoes, first published in English in 1959. The book includes reproductions of 50 rock paintings, showing people with herds of animals. The paintings are abundant and of superb artistic quality, comparable with the famous cave paintings at sites in France and Spain.

The Saharan rock paintings are actually more recent than the cave paintings; they were probably painted over a period of several thousand years, up until roughly 5,000 years ago. They are strong evidence that the Sahara was wet at that time. There appears to have been enough rain to support herds of cows and giraffes, which must have grazed on grass and trees. There were also some hippopotamuses and elephants, suggesting that the Sahara must have been like the Serengeti today.

At roughly the same point in the earth’s history, there were also trees standing in mountain valleys in Switzerland, valleys that are now filled with famous glaciers; these glaciers, which are shrinking, were smaller then than now. Six thousand years ago seems to have been the warmest and wettest period of the interglacial era, which began 12,000 years ago (when the last ice age ended).

Given the current warming trend, I would like to ask the following two questions: First, if the modern increase of carbon dioxide in the atmosphere continues, shall we arrive at a climate similar to the climate of 6,000 years ago, when the Sahara was wet? Second, if we could choose between the climate of today with a dry Sahara and the climate of 6,000 years ago with a wet Sahara, should we prefer the climate of today? Since I am a heretic, I am inclined to answer yes to the first question and no to the second.


Freeman Dyson is a futurist and professor emeritus of physics at the Institute for Advanced Study in Princeton, New Jersey.

Originally published March 22, 2006

Tags

Share this Stumbleupon Reddit Email + More

Now on SEEDMAGAZINE.COM

  • Ideas

    I Tried Almost Everything Else

    John Rinn, snowboarder, skateboarder, and “genomic origamist,” on why we should dumpster-dive in our genomes and the inspiration of a middle-distance runner.

  • Ideas

    Going, Going, Gone

    The second most common element in the universe is increasingly rare on Earth—except, for now, in America.

  • Ideas

    Earth-like Planets Aren’t Rare

    Renowned planetary scientist James Kasting on the odds of finding another Earth-like planet and the power of science fiction.

The Seed Salon

Video: conversations with leading scientists and thinkers on fundamental issues and ideas at the edge of science and culture.

Are We Beyond the Two Cultures?

Video: Seed revisits the questions C.P. Snow raised about science and the humanities 50 years by asking six great thinkers, Where are we now?

Saved by Science

Audio slideshow: Justine Cooper's large-format photographs of the collections behind the walls of the American Museum of Natural History.

The Universe in 2009

In 2009, we are celebrating curiosity and creativity with a dynamic look at the very best ideas that give us reason for optimism.

Revolutionary Minds
The Interpreters

In this installment of Revolutionary Minds, five people who use the new tools of science to educate, illuminate, and engage.

The Seed Design Series

Leading scientists, designers, and architects on ideas like the personal genome, brain visualization, generative architecture, and collective design.

The Seed State of Science

Seed examines the radical changes within science itself by assessing the evolving role of scientists and the shifting dimensions of scientific practice.

A Place for Science

On the trail of the haunts, homes, and posts of knowledge, from the laboratory to the field.

Portfolio

Witness the science. Stunning photographic portfolios from the pages of Seed magazine.

SEEDMAGAZINE.COM by Seed Media Group. ©2005-2012 Seed Media Group LLC. All Rights Reserved.

Sites by Seed Media Group: Seed Media Group | ScienceBlogs | Research Blogging | SEEDMAGAZINE.COM