The Pleistocene "Ice Age," which began 2 million years ago and ended 10,000 years ago, was just the latest of at least six glacial epochs in the 4.6 billion year history of our planet. And if the Pleistocene was typical of the other ice ages, they were characterized by intermittent periods of glacial formation and glacial retreat, as the climate cooled and warmed. During the Pleistocene, there were four major episodes of glaciation, separated by warm, interglacial periods.
We live in the Holocene Period, which began 10,000 years ago. Most climatologists believe that this is just another interglacial period and that our climate will begin to cool in another 5-10,000 years. In fact, a brief period of cooling, often called the Little Ice Age, occurred from about 1300 to 1850 AD, when global temperatures dropped by 2-3 degrees C.; during this period, glaciers advanced, northern com-munities collapsed and crop failures were widespread. The cause for this brief ice age is uncertain but most evidence points toward decreased solar activity.
Today, as we hear several times each day, Earth's climate is warming. While man is certainly contributing with his indus-trial "greenhouse gases," other factors are surely at play. Most of the Pleistocene interglacials were much warmer than our present-day climate and climate cycles have occurred throughout Earth's history. Our focus on man's role, which began with the industrial revolution (120 years at most) is a reflection of our human-centered view of the Universe; we are, after all, "the culmination of God's creation." To think that our current global warming might be due to factors out of our control (like the solar activity level) is to question our own self-importance. And while we must try to minimize our impact on the ecosystems of our home planet, we cannot forget that nature's cycles developed long before we graced the scene.
