Scientific conclusions should be based on observable facts, not political agendas. Yet politics is driving the global warming debate. Moreover, many environmentalists and political leaders take very radical stances, which they claim to base on science.

"Science, in the public arena, is commonly used as a source of authority with which to bludgeon political opponents and propagandize uninformed citizens," climate scientist Dr. Richard Lindzen once lamented in the Wall Street Journal. "This is what has been done with both the reports of the IPCC and the NAS. It is a reprehensible practice that corrodes our ability to make rational decisions."

Yet rational decisions can be made. All that is necessary is to separate the politics from the science and examine the known facts:

• Climate variability: The climate is constantly changing, not just season to season but year to year, century to century, and millennium to millennium. In his Journal article, Dr. Lindzen pointed out that "two centuries ago, much of the Northern Hemisphere was emerging from a little ice age. A millennium ago, during the Middle Ages, the same region was in a warm period. Thirty years ago, we were concerned with global cooling." During the global cooling scare of the 1970s, some observers even worried that the planet was on the verge of a new ice age.
• The actual temperature record: The global mean temperature is approximately 0.5 degrees Celsius higher than it was a century ago. Based on surface readings, the temperature rose prior to 1940, perhaps in response to the end of the little ice age, which lasted until the 19th century. From about 1940 until about 1975, the temperature dropped, sparking the above-mentioned global cooling scare. More recently the temperature has been rising again, sparking concerns about global warming.
  The accuracy of the surface temperature record must be kept in mind when evaluating trends measured in fractions of a degree. One significant problem is the extent to which the data may be skewed as a result of urbanization. Atmospheric physicist Dr. S. Fred Singer wrote in a letter that appeared in the May issue of Science: "The post-1940 global warming claimed by the IPCC comes mainly from distant surface stations and from tropical sea surface readings, with both data sets poorly controlled (in both quality and location)." On the other hand, "surface data from well-controlled U.S. stations (after removing the urban ‘heat-island’ effects) show the warmest years as being around 1940." In his testimony to the Senate Commerce Committee on July 18th of last year, Singer bluntly stated: "The post-1980 global warming trend from surface thermometers is not credible."
  Dr. Singer, who established the U.S. Weather Satellite Service and served as its first director, is just one of many scientists who believe that temperature data collected by weather satellites provides a far better measuring stick than the surface readings. After all, the satellite data is truly global, and it is not skewed by the urban heat effect. The satellite data from January 1979 (when this data first became available) through May 2001 shows a warming trend of 0.038 degrees Celsius per decade — or less than four-tenths of one degree per century. This minuscule rate of increase, which could change, is far less than the dramatic increases in temperature the forecasters of doom have been warning against.
• Man's effect on the climate: In the interest of scrupulous accuracy, Dr. Lindzen acknowledged in his May 2nd Senate testimony that "man, like the butterfly, has some impact on climate." Obviously this was true when the Vikings were able to cultivate Greenland, Iceland, and Newfoundland. But it is true even today. In the April 3rd issue of the Wall Street Journal, George Melloan noted that, according to "serious scientists," "the greenhouse gases are a fundamental part of the biosphere, necessary to all life, and … industrial activity generates less than 5% of them, if that."
• Carbon dioxide's effect on climate: According to the global warming theory, the increase of carbon dioxide in the atmosphere, which has been established, is causing the global temperature to rise. Most of the increase in the surface temperature during the past century occurred before most of the increase in atmospheric CO2. The temperature in 1940, recall, was not much different than it is now. Yet, as astrophysicist Sallie Baliunas pointed out in a letter published in the August 5, 1999 Wall Street Journal, "more than 80% of the manmade carbon dioxide has entered the air since the ’40s."
  One reason why the global warming theory may be flawed is that the amount of atmospheric CO2 is not the only variable determining the earth’s temperature. It is not even the main "greenhouse" gas. In a chapter appearing in the compendium Earth Report 2000, Dr. Roy Spencer, senior scientist for climate studies at NASA’s Marshall Space Flight Center, noted: "It is estimated that water vapor accounts for about 95 percent of the earth’s natural greenhouse effect, whereas carbon dioxide contributes most of the remaining 5 percent. Global warming projections assume that water vapor will increase along with any warming resulting from the increases in carbon dioxide concentrations."
  The projected "positive feedback" to the initial CO2-induced warming may not occur to the extent that global warming theorists are predicting, however. As Dr. Spencer points out, "there remain substantial uncertainties in our understanding of how the climate system will respond to increasing concentrations of carbon dioxide and other greenhouse gases." Moreover, the natural greenhouse effect that heats the earth is moderated by natural cooling processes. "In other words," concluded Dr. Spencer, "the natural greenhouse effect cannot be considered in isolation as a process warming the earth, without at the same time accounting for cooling processes that actually keep the greenhouse effect from scorching us all."
• The sun's effect on climate: One factor global warming theorists ignore is the effect that the sun’s changing activity may have on the global temperature. A brighter sun may cause the global temperature to rise, and vice versa. Dr. Baliunas, in the Wall Street Journal letter referenced above, explained how the sun’s activity can be measured by the length of the sunspot cycle (the shorter the cycle, the more active the sun). Dr. Baliunas’ letter included a chart showing a close correlation between changes in the length of the sunspot cycle and Northern Hemisphere land temperature for 1750-1978.