The Venus syndrome

Dr. James Hansen, NASA’s Goddard Space Institute Director, is predicting that we are heading to a point of no return, a catastrophic tipping point of the Earth climate, if we continue to burn all available fossil fuels. He calls it the Venus syndrome. On page 23 of his lecture he says:

“The Earth’s climate becomes more sensitive as it becomes very cold, when an amplifying feedback, the surface albedo, can cause a runaway snowball Earth, with ice and snow forming all the way to the equator. If the planet gets too warm, the water vapor feedback can cause a runaway greenhouse effect. The ocean boils into the atmosphere and life is extinguished. The Earth has fell off the wagon several times in the cold direction, ice and snow reaching all the way to the equator. Earth can escape from snowball conditions because weathering slows down, and CO2 accumulates in the air until there is enough to melt the ice and snow rapidly, as the feedbacks work in the opposite direction. The last snowball Earth occurred about 640 million years ago.” Now the danger that we face is the Venus syndrome. There is no escape from the Venus Syndrome. Venus will never have oceans again.”

This scenario is maybe a bit exaggerated: oceans existed on earth long before life and at a much higher level of CO2. But at the time, 3-4 billion years ago, the Sun may have been weaker, too… And I believe that global warming in its worst form combined with burning of all fossil fuels could in fact be a severe threat to the existence of human life on earth. The oxygen in the air is basically a pollution of the atmosphere caused by life itself. Originally, there was little O2 in the atmosphere, but much CO2. As a study reports, CO2 was more than 10 to 200 times today’s level 1.4 billion years ago. If life can produce oxygen, it can also consume it again. When all fossil fuels are burnt and the last rainforest vanishes, then obviously this would change the composition of the atmosphere: the amount of CO2 increases while the amount of O2 decreases. In earth’s atmosphere there is now 20% oxygen and 0.039% (390 parts per million or ppm) carbon dioxide. If the ratio would be reversed, then no higher life forms would be possible.