Story highlights Scientists and journalists are worried about the condition of the planet for their own children and grandchildren, writes David Ray Griffin

The threat to civilization comes primarily from the increase of the level of carbon dioxide (CO2) in the atmosphere, he says

Griffin: The burning of coal, oil, and natural gas has made the planet warmer than it had been since the rise of civilization 10,000 years ago

The resulting threat of runaway global warming is not merely theoretical, he writes

David Ray Griffin is emeritus professor of philosophy of religion at Claremont School of Theology and Claremont Graduate University. His most recent book is Unprecedented: Can Civilization Survive the CO2 Crisis? The views expressed in this commentary are solely those of the author.

(CNN) Although most of us worry about other things, climate scientists have become increasingly worried about the survival of civilization. For example, Lonnie Thompson, who received the U.S. National Medal of Science in 2010, said that virtually all climatologists "are now convinced that global warming poses a clear and present danger to civilization."

Informed journalists share this concern. The climate crisis "threatens the survival of our civilization," said Pulitzer Prize-winner Ross Gelbspan. Mark Hertsgaard agrees, saying that the continuation of global warming "would create planetary conditions all but certain to end civilization as we know it."

These scientists and journalists, moreover, are worried not only about the distant future but about the condition of the planet for their own children and grandchildren. James Hansen, often considered the world's leading climate scientist, entitled his book "Storms of My Grandchildren."

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The threat to civilization comes primarily from the increase of the level of carbon dioxide (CO2) in the atmosphere, due largely to the burning of fossil fuels. Before the rise of the industrial age, CO2 constituted only 275 ppm (parts per million) of the atmosphere. But it is now above 400 and rising about 2.5 ppm per year.

Because of the CO2 increase, the planet's average temperature has increased 0.85 degrees Celsius (1.5 degrees Fahrenheit). Although this increase may not seem much, it has already brought about serious changes.