In contrast with Dr. Mann's conclusion, the current modest temperature trend is consistent in both magnitude and timing with the natural temperature cycles that the earth has been experiencing for millions of years, and it is nothing to fear.

The earth's climate cycles result from a number of long- and short-term driving forces. Long-term cycles, which include a 100,000-year orbital eccentricity cycle, a 41,000-year axis tilt angle cycle and a 23,000-year orbital "wobble" cycle, are responsible for major ice ages and interglacial periods.

Superposed on top of the long-term climate fluctuations are smaller and shorter climate cycles that have a period of roughly 1,500 years, theorized to result from solar variation.

Convincing evidence for these short-term cycles has been found all over the world. Originally, these 1,500-year cycles were discovered by studying radioactive isotopes in ice cores taken from Greenland, which provided a 250,000-year geologic record. Similar results have been uncovered on the opposite side of the world in Antarctic ice cores.

Hundreds of peer-reviewed articles in the world's leading scientific journals have documented additional evidence using a variety of proxies from all over the world. These include coral samples, cave stalagmites, tree rings, ocean glacial deposition, pollen deposition, bore holes and fossils, as summarized by renowned scientist and skeptic of the current CO2 hysteria, Dr. S. Fred Singer, in his recent New York Times best seller, "Unstoppable Global Warming: Every 1,500 Years."

Historical records from a broad geographic sampling corroborate the physical evidence. For example, records showed that the agricultural range of temperature-sensitive plants expanded and contracted in a manner consistent with the temperature cycle.

The current modest warming trend is the predictable temperature rise in the 1,500-year cycle following the "Little Ice Age," which lasted from 1300 to 1850. For its part, the Little Ice Age followed the Medieval Warming Period, which followed the Dark Ages cooling period, which followed the "Roman Warming Period," which followed another cold period before that and so on for millions of years.

Should we be concerned? Not if history is a guide — warm periods in the world's climate have historically been prosperous and bountiful, while the colder cycles have been characterized by mass starvation, disease, increased weather severity and civil unrest.