01 Jun 1998 Sun to Blame for Global Warming, by John Carlisle

Those looking for the culprit responsible for global warming have missed the obvious choice – the sun. While it may come as a newsflash to some, scientific evidence conclusively shows that the sun plays a far more important role in causing global warming and global cooling than any other factor, natural or man-made. In fact, what may very well be the ultimate ironic twist in the global warming controversy is that the same solar forces that caused 150 years of warming are on the verge of producing a prolonged period of cooling.

The evidence for future cooling is supported by considerable scientific research that has only recently begun to come to light. It wasn’t until 1980, with the aid of NASA satellites, that scientists definitively proved that the sun’s brightness – or radiance – varies in intensity, and that these variations occur in predictable cyclical patterns. This was a crucial discovery because the climate models used by greenhouse theory proponents always assumed that the sun’s radiance was constant. With that assumption in hand, they could ignore solar influences and focus on other influences, including human.

That turned out to be a reckless assumption. Further investigation revealed that there is a strong correlation between the variations in solar irradiance and fluctuations in the Earth’s temperature. When the sun gets dimmer, the Earth gets cooler; when the sun gets brighter, the Earth gets hotter. So important is the sun in climate change that half of the 1.5° F temperature increase since 1850 is directly attributable to changes in the sun. According to NASA scientists David Lind and Judith Lean, only one-quarter of a degree can be ascribed to other causes, such as greenhouse gases, through which human activities can theoretically exert some influence.

The correlation between major changes in the Earth’s temperature and changes in solar radiance is quite compelling. A perfect example is the Little Ice Age that lasted from 1650 to 1850. Temperatures in this era fell to as much as 2° F below today’s temperature, causing the glaciers to advance, the canals in Venice to freeze and major crop failures. Interestingly, this dramatic cooling happened in a period when the sun’s radiance had fallen to exceptionally low levels. Between 1645 and 1715, the sun was in a stage that scientists refer to as the Maunder Minimum. In this minimum, the sun has few sunspots and low magnetism which automatically indicates a lower radiance level. When the sun began to emerge from the minimum, radiance increased and by 1850 the temperature had warmed up enough for the Little Ice Age to end.

The Maunder Minimum is not an isolated event: it is a cyclical phenomenon that typically appears for 70 years following 200-300 years of warming. With only a few exceptions, whenever there is a solar minimum, the Earth gets colder. For example, Europe in the 13th and 15th Centuries experienced significantly lower temperatures and in both cases the cold spells coincided with a minimum. Similar correlations were found in the 9th Century and again in the 7th Century. Since 8700 B.C., there have been at least ten major cold periods similar to the Little Ice Age. Nine of those ten cold spells coincided with Maunder Minima.

There is no reason to believe that this 10,000-year-old cycle of solar-induced warming and cooling will change. Dr. Sallie Baliunas, an astrophysicist with the Harvard-Smithsonian Center for Astrophysics and one of the nation’s leading experts on global climate change, believes that we may be nearing the end of a solar warming cycle. Since the last minimum ended in 1715, Baliunas says there is a strong possibility that the Earth will start cooling off in the early part of the 21st Century.

Indeed, it could already be happening. Of the 1.5° F in warming the planet experienced over the last 150 years, two-thirds of that increase, or one degree, occurred between 1850 and 1940. In the last 50 years, the planetary temperature increased at a significantly slower rate of 0.5° F – precisely when dramatically increasing amounts of man-made carbon dioxide emissions should have been accelerating warming. Further buttressing the arguments for future cooling is the evidence from NASA satellites that the global temperature has actually fallen 0.04° F since 1979.

Of course, it is impossible to precisely predict when solar radiance will drop and global temperatures will begin falling. But one thing is certain: There is little evidence that mankind is responsible for global warming. There is considerable evidence that the sun causes warming and will most likely stimulate cooling in the not so distant future.

John K. Carlisle is the Director of The National Center for Public Policy Research’s Environmental Policy Task Force. Comments may be sent to [email protected].