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Any student of environmental change quickly learns that many popular predictions of the effects of future climate change and sea-level rise in the Pacific (and elsewhere) are highly, and unhelpfully, exaggerated. Such natural changes are also far from unprecedented, although the predicted rates of twenty-first-century change may indeed be so. The specter of future sea-level rise is one that has loomed large over the Pacific countless times before. The principal difference with the situation today is that, for the first time in human history, we can predict with a high degree of certainty that temperature and sea level will rise and by how much they will do so. So the specter is no longer ethereal; it can be discerned and its effects anticipated. The other important difference is that the human societies of the Pacific are far more vulnerable today than they were once to the effects of future climate change and sea-level rise. This is both because people are more settled in particular places—they cannot move so readily—and because there are far more people living today in the lowerlying parts of the Pacific than there have ever been. Together these two considerations are understandably causing a great deal of anxiety. The Intergovernmental Panel on Climate Change, the body established by the United Nations in 1988 to look specifically at the nature and effects of future climate and sea-level change, estimates that average earth-surface temperature will rise by 1.4–5.8°C between 1990 and 2100, and sea level will rise 9–88 cm in the same period. Given that in the period 1900–2000, temperatures in the Pacific rose by around 0.6°C and sea level by around 15 cm, it looks like there will be a significant acceleration in both temperature and sea-level rise this century. Specifically, the rate of temperature rise will be at least 2.3 times faster this century, perhaps more than nine times faster. The rate of sea-level rise may be nearly six times faster. Much of the variation in these estimates depends on how earth systems respond to the global warming that is thought to be driving these changes.1 During the twentieth century, temperature rise and sea-level rise caused significant Vanished Islands of the Future 10 vanished islands of the future 183 changes to the Pacific that have impacted on its people and their livelihoods. Principal among these has been the loss of lowlands by seawater inundation, erosion, and groundwater salinization. Also, as discussed in the next section, recent sea-level rise has probably been responsible for the erasure of some surficial islands off the map of the Pacific. If sea level rises as projected during the twenty-first century, more will undoubtedly vanish. One of the main reasons for writing this book is to raise awareness about particular geohazards in the Pacific. To this end, in the final section of this chapter there is a discussion of what we can learn about geohazards from the study of vanished islands. Short-Term Changes in Pacific Geography The ocean surface (sea level) is never still. Even were it perfectly flat for as far as the eye could see from a particular coast, it still would rise and fall every day. There are also changes that occur regularly every month and within the course of a single year. Then there are the less-regular, and less easily predictable, intra-annual changes, such as those associated with El Niño events. Then finally there are longer-term changes, barely discernible within a human life span, that range from those taking place over centuries to those taking place over millennia. Currently the world is experiencing a period of sea-level rise. As far as we can tell, this began about AD 1800 at the end of the Little Ice Age during the 400 years of which sea level had been consistently low compared with more recent times. About AD 1800, for reasons we do not completely understand, sea level began rising and, despite some variation,2 has been doing so ever since. As noted earlier, the best-possible estimate of future sea-level changes (to AD 2100) is that sea level will continue to rise, almost certainly accelerating within the next few decades (Figure 10.1). Just as it is clear that sea-level rise over the past hundred years brought about significant environmental and societal changes in the Pacific Basin...


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