Survival of the Sickest: The Surprising Connections Between Disease and Longevity. Jonathan Prince

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      Of course, there were some contrary voices singing a different tune, but the larger scientific community paid them very little regard. Andrew Ellicott Douglass was an astronomer working in Arizona in 1895 when he first started cutting down trees to examine them for evidence of any effect from a specific solar activity, called sunspots, that occurs in cycles. He never found that – but he did ultimately invent dendrochronology, the scientific technique of studying tree rings for clues about the past. One of his first observations was that tree rings were thinner during cold or dry years and thicker during wet or warm years. And by rolling back the years, one ring at a time, he discovered what appeared to be a century-long climate change that occurred around the seventeenth century, with a significant drop in temperature. The reaction of the scientific community was a collective “Nah.” As far as the climate change community was concerned, Douglass was cutting down trees in a forest with nobody there to hear it. (According to Dr. Lloyd Burckle of Columbia University, not only was Douglass right: the hundred-year cold spell he discovered was responsible for some beautiful music. Burckle says the superior sound of the great European violin makers, including the famous Stradivari, is the result of the high-density wood from the trees that grew during this century-long freeze – denser because they grew less during the cold and had thinner rings as a result.)

      More evidence of the possibility of rapid climate change accumulated. In Sweden, scientists studying layers of mud from lake bottoms found evidence of climate change that occurred much more quickly than anyone at the time thought possible. These scientists discovered large amounts of pollen from an Arctic wildflower called Dryas octopetala in mud cores from only 12,000 years ago. Dryas’s usual home is the Arctic; it only truly flourished across Europe during periods of significant cold. Its widespread prevalence in Sweden around 12,000 years ago seemed to indicate that the warm weather that had followed the last ice age had been interrupted by a rapid shift back to much colder weather. In honor of the telltale wildflower, they named this arctic reprise the Younger Dryas. Of course, given prevailing thinking, even these scientists believed that the “rapid” onset of the Younger Dryas took 1,000 years or so.

      It’s hard to underestimate the chilling effect conventional wisdom can have on the scientific community. Geologists of the time believed the present was the key to the past – if this is the way the climate behaves today, that’s the way it behaved yesterday. That philosophy is called uniformitarianism and, as the physicist Spencer Weart points out in his 2003 book The Discovery of Global Warming, it was the guiding principle among scientists of the time:

      Through most of the 20th century, the uniformitarian principle was cherished by geologists as the very foundation of their science. In human experience, temperatures apparently did not rise or fall radically in less than millennia, so the uniformitarian principle declared that such changes had never happened in the past.

      If you’re positive something doesn’t exist, you’re not going to look for it, right? And because everyone was certain that global climate changes took at least a thousand years, nobody even bothered to look at the evidence in a way that could reveal faster change. Those Swedish scientists studying the layers of lake bottom clay who first postulated the “rapid” thousand-year onset of the Younger Dryas? They were looking at chunks of mud spanning centuries; they never looked at samples small enough to demonstrate faster change. The proof that the Younger Dryas descended on the Northern Hemisphere much more rapidly than they thought was right in front of their eyes – but they were blinded by their assumptions.

      By the 1950s and 1960s, the uniformitarian vise started to lose its hold, or at least change its grip, as scientists began to understand the potential of catastrophic events to produce rapid change. In the late 1950s, Dave Fultz at the University of Chicago built a mock-up of the earth’s atmosphere using rotating fluids that simulated the behavior of atmospheric gases. Sure enough, the fluids moved in stable, repeating patterns – unless, that is, they were disturbed. Then, even the smallest interference could produce massive changes in the currents. It wasn’t proof by a long shot, but it certainly was a powerful suggestion that the real atmosphere was susceptible to significant change. Other scientists developed mathematical models that indicated similar possibilities for rapid shifts.

      As new evidence was discovered and old evidence was re-examined, the scientific consensus evolved. By the 1970s there was general agreement that the temperature shifts and climate changes leading into and out of ice ages could occur over mere hundreds of years. Thousands were out, hundreds were in. Centuries were the new “rapid.”

      There was a new consensus around when – but a total lack of agreement about how. Perhaps methane bubbled up from tundra bogs and trapped the heat of the sun. Perhaps ice sheets broke off from the Antarctic and cooled the oceans. Maybe a glacier melted into the North Atlantic, creating a massive freshwater lake that suddenly interrupted the ocean’s delivery of warm tropical water to the north.

      It’s fitting that hard, cold proof was eventually found in hard, cold ice.

      In the early 1970s, climatologists discovered that some of the best records of historic weather patterns were filed away in the glaciers and ice plateaus of northern Greenland. It was hard, treacherous work – if you’re imagining the stereotypical lab rat in a white coat, think again. This was Extreme Sports: Ph.D. – multinational teams trekking across miles of ice, climbing thousands of feet, hauling tons of machines, and enduring altitude sickness and freakish cold, all so they could bore into a two-mile core of ice. But the prize was a pristine and unambiguous record of yearly precipitation and past temperature, unspoiled by millennia and willing to reveal its secrets with just a little chemical analysis. Once you paid it a visit, of course.

      By the 1980s, these ice cores definitively confirmed the existence of the Younger Dryas – a severe drop in temperature that began around 13,000 years ago and lasted more than a thousand years. But that was just, well, the tip of the iceberg.

      In 1989 the United States mounted an expedition to drill a core all the way to the bottom of the two-mile Greenland ice sheet – representing 110,000 years of climate history. Just twenty miles away, a European team was conducting a similar study. Four years later, both teams got to the bottom – and the meaning of rapid was about to change again.

      The ice cores revealed that the Younger Dryas – the last ice age – ended in just three years. Ice age to no ice age – not in three thousand years, not in three hundred years, but in three plain years. What’s more, the ice cores revealed that the onset of the Younger Dryas took just a decade. The proof was crystal clear this time – rapid climate change was very real. It was so rapid that scientists stopped using the word rapid to describe it, and started using words like abrupt and violent. Dr. Weart summed it up in his 2003 book:

      Swings of temperature that scientists in the 1950s believed to take tens of thousands of years, in the 1970s to take thousands of years, and in the 1980s to take hundreds of years, were now found to take only decades.

      In fact, there have been around a score of these abrupt climate changes over the last 110,000 years; the only truly stable period has been the last 11,000 years or so. Turns out, the present isn’t the key to the past – it’s the exception.

      The most likely suspect for the onset of the Younger Dryas and the sudden return to ice age temperatures across Europe is the breakdown of the ocean “conveyor belt,” or thermohaline circulation, in the Atlantic Ocean. When it’s working normally – or at least the way we’re used to it – the conveyor carries warm tropical water on the ocean surface to the north, where it cools, becomes denser, sinks, and СКАЧАТЬ