The Ice Chronicles: The Quest to Understand Global Climate Change

3 | The Discovery of Rapid Climate Change Events (RCCEs) and the Realization that Climate Has Multiple Controls

ç 3 The Discovery of Rapid Climate Change Events (RCCEs) and the Realization that Climate Has Multiple Controls I magine our early ancestors living within a few hundred miles of the vast ice sheets that covered much of the high latitudes of the Northern Hemisphere some 12,000 to 70,000 years ago (see fig.3.1). They were accustomed to cold winters and harsh winds, but every 1,500 years or so the winds became stronger, pushed violently out of the north, and the winters lasted all year. These conditions might have persisted for decades, even centuries, forcing our ancestors to move southward . The change was so rapid that it occurred within a lifetime, which at that time might have been only twenty to thirty years. In fact, it happened so quickly that it might have been noticed by people in some areas in less than two years. Imagine also the tiny population of humans living about 50,000 years ago, perhaps fewer than 100,000 (Asimov and White, 1990). If only a small percentage of the population experienced an invasion of terrible winds choked with dust, isn’t it possible that stories would have been passed from generation to generation, urging people to fear the “terrible demons of the north”? After all, the winds, in the minds of those early peoples, came from the mouths of demons and dragons. The Ice Chronicles tell us that a scientific reality lurks behind these myths. Imagine also that today, the winds suddenly increased and the winters lasted much longer, so that heating bills quadrupled, airline flights were frequently cancelled because of storms, and ice and snow brought most f i g u r e 3.1. Changes in the distribution of ice sheets over North America and Greenland during the stages from maximum extent of the ice sheet (21,000 to 17,000 years ago) to the last major remnants of the ice sheet (7,000 years ago). Modified from Mayewski et al., 1981. northern cities to a standstill ten or twenty times per winter. Now we have the scientific tools to determine the likelihood of such a scenario. Since GISP2 hit rock bottom in Greenland in 1993, scientists around the world have been energetically analyzing more than 100,000 years of the Earth’s climate history. So far, hundreds of papers have been published on the results of the expedition, and this work is likely to go on for years. GISP2, and subsequent supporting research, has already provided us with a raft of insights about how climate works. For the paleoclimatologist , the thrill of plotting real data on climate change over the span of many millennia is difficult to describe. It’s a bit like looking at the Holy Grail of climate research. For most people, however, GISP2 will probably be remembered, first and foremost, for its confirmation that Rapid Climate Change Events (RCCEs) are real, they are natural, and they have occurred many times in the past—even before human beings began to alter the Earth’s climate system on a vast scale. 82 The Ice Chronicles ç ç end-to-end science In 1970, on my second expedition to Antarctica as a graduate student , the National Science Foundation gave me the opportunity to show a U.S. Senator around a portion of the Transantarctic Mountains accessible from the main U.S. base, McMurdo Station. I had been selected for the honor because this was part of my research area. The senator and I spent a few hours together, and I felt comfortable enough with him to ask a question that was perhaps a bit odd, considering the circumstances. I said,“You know, I love working in Antarctica , but I wonder why the United States government supports the type of research we’re doing here.” My point was that the research was incredibly exciting to us but it was not obvious to me why taxpayers should cover the costs. After all, it was unclear how the work would ever benefit the people who were paying for it. His response had a profound effect on the rest of my career . He said, “In twenty-five years, what you are doing will turn out to have practical value for all of humanity.” I thought that was a very nice thing to say, but how could it be true? What possible value could research in the Antarctic wasteland have for the rest of...