An Old Friend Turned Enemy Stephen Fung February 7, 2007 Life on Earth would never had been possible without liquid water and new evidence shows that CO2 helped maintain the temperatures above freezing at a time when the young Sun was too weak to warm the surface of our planet. This gas, now considered a nuisance and held responsible for the current observed global warming, was once essential for the apparition of life and for preventing the Earth from suffering the same fate as Mars. Source: Science Daily Share This With The World!