2 - Greenhouse Earth

Summary

If this were a science fiction story, I would tell of the underground cities on Mars that get their heat from the still-warm core of the planet. I would tell of the underground cities on Venus too, and their struggle to insulate themselves from the killing heat of the surface. In the story I would sympathize with the Martians because through no fault of their own, they lived on a planet that was too small to keep its atmosphere and with it the greenhouse effect that kept it warm enough for liquid water to flow. As for the Venusians, I would write with sadness of their blindness to the dangers of global warming and the runaway greenhouse effect that forced them underground.

There is no question about the reality of the greenhouse effect, even from those who still deny that human activities have anything to do with global warming. This chapter and the next three tell the story of how we can be so sure there is an effect, why almost everyone has finally concluded that our planet is getting warmer and that we are primarily responsible for it, and what the future holds if we continue on our present course.

To understand the issues, we can call on information about other planets in our Solar System as well as on what we can measure on our own. We and our nearest neighbors, Venus, closer to the Sun, and Mars, further out, are very much alike in composition, but very different in surface temperatures because of the greenhouse effect. Venus is too hot to support life, and Mars is too cold. Yet all were formed about 4.5 billion years ago, and all are made from the same stuff. The difference lies in their greenhouse effects: too much for Venus, too little for Mars, and just right for us.