Introduction

Humankind's present-day dilemma with respect to global warming often is viewed with virtually no temporal perspective at all. The World Meteorological Organization reports that the decade 2001-2010 was the warmest on record, surpassing 1991-2000, which itself was warmer than previous decades. But how does this century compare to other centuries, or this millennium to others? In the third part of this book, we explore extremes of Earth climate far more profound than those experienced in modern times, or even through the short span of human history.

To really put global warming in perspective, however, we need to understand how the climate has varied during the penultimate geologic epoch, the Pleistocene, a time when all of Earth's geologic processes, and the chemistry of the atmosphere, are fully modern in every respect. The time since the last interglacial, through the last ice age to the present interglacial, is recent enough that evidence is available by which very detailed records of climate can be constructed. The most thorough records can be assembled for the past 10,000 years of Earth history, the Holocene. In this chapter, techniques for assembling detailed climate information are summarized, and we compare the climate in this interglacial with that in the last, a kind of “Jekyll and Hyde” story.