What Does the Story about human experiences of past natural climatic changes tell us in broad terms? At the least it points to the types of risks to the health, survival, and social stability of diverse populations likely to result from this century’s human- driven climate change. This chapter and the next look to that future, and to how humankind might avert the looming environmental and social crises. In preparation, paleoclimatologist Raymond Bradley argues that we should seek “insight into the nature and magnitude of past regional [climatic] anomalies and their human impacts by examining the Holocene paleoclimate record.” This chapter asks whether there are discernible patterns in the long story of past climate change and population health adversity. Have particular conditions and factors determined vulnerability to those adverse impacts? On this basis, how vulnerable are today’s populations, rich and poor, tropical and polar, to the climatic stressors and associated risks anticipated in this twenty- first century? An overview of the Holocene’s 11,000- year climatic experience, a mere sliver of the total Homo sapiens experience of climate variation, provides a good entry point. This latest of the nine interglacial periods during the past million years has been the one in which anatomically and behaviorally modern humans began exerting increasing control over the environment and its carrying capacity by shifting toward growing crops, herding animals, managing water flows, and building settlements. That agriculturally based era is shown near the top right in Figure 10.1, a moment in geological time. Throughout the Holocene, the climate was, as ever, naturally variable, and the gods of rain, sun, wind, and warmth held great sway over harvests, hunger, and viability. We will summarize here the main points from earlier chapters as the basis for a discussion of patterns in the past which may point to future vulnerability and implications for human well- being. The Holocene has been a period of relative climatic constancy, with an average global surface temperature of 15oC Changes in temperature and rainfall spanning several centuries have occurred, as have many shorter- term fluctuations.
