The Earth has been going through very long, very slow cycles of warming and cooling for hundreds of millions of years. We are currently in a warming phase that has included the melting of the massive ice sheets during the period of roughly 15,000 years ago to about 9,000 years ago.

There is concern about the problems that may be caused by continued warming. Earth has a wide range of local climates ranging from the hot, damp tropics to the cold, dry north, and elevations that vary from sea level to relatively high mountains. It would seem likely that continued warming will shift or enlarge the warmer areas toward or into the colder areas. This is not likely to be a problem, because the natural world has adapted and people have lived in the different local climates for a very long time.

Many people have already experienced climate change by simply moving from one local climate to another, such as moving from the northern areas of the United States to the Caribbean coast.

Climate changes very slowly over a very long time. It is likely that the great majority of people in the world will not perceive the effects of climate change during their lifetimes. The effects will probably be noticeable only to those who live in fringe areas or who engage in specialized work that is sensitive to climate change.

David W. Knudsen


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