What is some of the evidence presented to support the global warming theory?
Over the last few years, the press has been filled with stories purported to “prove” that human intervention with the greenhouse mechanism is producing the global warming that the computer models (which are far from perfect tools) suggest might hap pen. Some are listed below. But it should be remembered that climate varies naturally all the time. While global warming as a theory has been widely debated, actual measurements that support the theory are hard to come by.
May 1991 was hotter than usual in Kentucky. Louisville had the warmest May in 149 years of record. Lexington also had its warmest May in over a century. Curiously, no daily record highs were broken anywhere in the state during the month.
Some evidence seems to indicate that it’s getting drier as well. Yearly precipitation over land areas of our planet declined in the 1980s following a three-decade trend towards wetter conditions. It’s much too early to tell, however, if this is an effect of global warming or just part of the natural climate cycle.
One possible impact of global warming may be increased amounts of water flowing through U.S. streams during the cold season. This seems to contradict the notion that the planet is getting drier; such contradictions are typical of many of the pronouncements concerning the evidence for global change.
In the period 1941—88, increasing levels of water flowing through U.S. rivers and streams, especially in autumn and winter, may be one indication of some systematic climate change. Unfortunately, periodic summer droughts do not seem to have been canceled out.
The polar ocean ice sheets have long been suspected to be sensitive indicators of global temperature. Satellite observations did show a two percent shrinkage over an eight-year period in the 1980s in the Arctic Ocean. No change was noted in South Polar regions, however.
Whether global warming due to human activities is just a theoretical prediction or something that is already occurring is a hotly debated topic in atmospheric sciences. Temperature data from surface stations around the world are beginning to show some apparent signs of the predicted warming. The period 1991 - 95 was the warmest half-decade on record, with 1995 setting a record high in the 140 years of reliable global temperature data. British researchers believe the planet is now warming at the rate of 0.2°C per decade. Globally, the years 1990 and 1991 were two of the warmest years since worldwide records began during the last century. This does not yet prove, however, that widespread global warming is underway, but it is one piece of evidence.
By most measures the winter of 1991 - 92 was the warmest on record in the 48 contiguous United States. January 1990 was noted for its warmth over much of the United States. For the first time in over a century some northern plains cities had no minimum temperatures of 0°F or less.