First, let me establish my credentials. I have a Ph.D. in chemistry from an Ivy League university, and have worked as an environmental chemist, as well as an ozone chemist. Yes, ozone, that toxic gas which is both a dangerous pollutant and essential to protect us from UV radiation and keep us from getting skin cancer. I am also an "environmentalist," and have led back-country outings for national organizations.
The environmental movement predicts that "the effects of man made climate change will lead to more 'freak' weather conditions, massive displacement of populations, potentially enormous loss of life, greater risk from diseases, and extinction of species." These predictions may have some truth in them, but what has happened without the help of man makes them look pretty trivial.
We should all be aware that global warming has been going on for a very long time. I refer readers to the government websites http://www.gcrio.org/CONSEQUENCES/winter96/geoclimate.html and http://ga.water.usgs.gov/edu/earthglacier.html and an article in Science 288, 1033-1035, May 12, 2000.
The article in the "gcrio" on-line magazine, "Consequences," shows that during the so-called Medieval Warm Period, between about the years 1050 and 1250, the temperature was somewhat higher than it is now. If we look back further, it was a lot warmer between about 4000 and 7000 years ago. It's hard to see how man could have caused those high temperatures. 125,000 years ago it was warmer still.
The USGS website says that "if all glaciers melted today the seas would rise about 260 feet." The Science article shows that the sea level has risen almost 400 ft in the past 22,000 years, and the EPA reports that the sea level is now rising at the rate of 10-12 inches per century. If we calculate an average rate of sea level rise from the Science article, it comes out 22 inches per century, so the current rate of sea level rise is slower than the average for the past 22,000 years. We have no reason to think that sea level rise will stop here, whether mankind stops adding greenhouse gases or not. Something other than the works of MAN has caused the sea level to rise 400 ft in the past 22,000 years!
If the sea level rises 260 ft, most of the big cities, and a lot of the cropland in the United States will be under water. Boston, New York City, Philadelphia, Baltimore, Washington DC, Miami, New Orleans, Houston, Los Angeles, San Francisco, Tacoma, and Seattle will all be deep under water. Louisville, St. Louis, Chicago, Phoenix, and Denver will be the only big cities in the US that will be on dry land.
Additional evidence of sea level rise during ancient history is the number of sunken cities in the Mediterranean and Black Seas that are now being explored by archaeologists. The same event that flooded them is very likely the source of the legend of Atlantis, and is almost certainly the source of the stories of Noah’s and Deucalion’s floods.
The climate has also changed as a result of these sea level and/or temperature changes. For example, the South Sahara, which is one of the driest deserts on earth, was green and fertile at the time of the Tassili Frescos, 6000 BC. The climate also changed over shorter time scales, like the relatively wet time in the desert southwest during the Medieval Warm Period. That was the time when the Anasazi were most prominent, and when it ended, the Anasazi disappeared.
About 15,000 years ago, the sea level was so low that humans crossed the dry Bering Straits, and settled in the Western Hemisphere. The large North American mammals, such as elephants, horses, camels, great cats, etc., became extinct, probably because of man’s over-hunting.
How about those for examples of "freak weather conditions, massive displacement of populations, potentially enormous loss of life, greater risk from diseases, and extinction of species!"
Rather than try to stop global warming, for which man may or may not be responsible, and over which he may have no control, we had better focus our attention on learning to live with the changes that nature has caused in the past, and will almost certainly cause in the future.