We live in a cold world compared to the geological near past.
Now, naturally, there is concern among some that the climate may be warming a bit. After all, it has been hundreds of thousands of years since mankind left the tropics to settle in colder areas of the planet. Certainly, our life-styles could be affected by warmer average global temperatures.
But, by and large, the earth remains a cold planet compared to the planet it was when there was an expansion of the diversity of life during its lush period 50-60 million years ago (98% point of life's timeline on this planet... beginning about 2.5 billion years ago). In fact, our current condition is a planet that is rather sparse with life comparatively.
Nature has a way of changing things despite our best efforts at trying to control everything. Little things like the gap between North and South America closing certainly did more than man could ever hope to accomplish. Sure, we may have some influence on the change, but we have a long way to go before the arctic reaches 74 degrees F again (Alaska averages between 10 and 40 degrees F).
The real question is: would we have a more or less habitable world... not just for man? I don't believe that question has really been posed... much less answered.
