With Speed and Violence: Why Scientists Fear Tipping Points in Climate Change by Fred Pearce Read Free Book Online

extent of the damage we are doing to our planetary home. We often see our impact as limited to individual parts of the system: to trashed rainforests, polluted oceans, and even raised air temperatures. We rarely notice that by doing all these things at once, we are undermining the basic planetary systems. Something, Steffen says, is going to give: "The planet may have an Achilles heel. And if it does, we badly need to know about it." Without that knowledge and the will to act, he says, the Anthropocene may well end in tears.
    A report from the U.S. National Academy of Sciences in 2002, under the chairmanship of Richard Alley, of Penn State University-a glaciologist with the slightly manic appearance of an ex-hippie, who has become a regular on Capitol Hill for his ability to talk climate science in plain language-sounded a similar warning. "Recent scientific evidence shows that major and widespread climate changes have occurred with startling speed," the report began. "The new paradigm of an abruptly changing climate system has been well established by research over the last decade, but this new thinking is little known and scarcely appreciated in the wider community of natural and social scientists and policymakers." Or, Alley might have added, among the citizens of this threatened planet.
    We have already had one lucky break. It happened twenty years ago, when a hole suddenly opened in the ozone layer over Antarctica, stripping away the continent's protective shield against ultraviolet radiation. We were lucky that it happened over Antarctica, and lucky that we spotted it before it spread too far.
    Many of the scientists who worked to unravel the cause of the ozone hole-including Crutzen, who won his Nobel Prize in this endeavor-are among the most vehement in issuing the new warnings. They know how close we came to disaster. Glaciologists like Alley are another group who take the perils of the Anthropocene most seriously. In the past decade, they have analyzed ice cores from both Greenland and Antarctica to map the patterns of past natural climate change. The results have been chilling.

    It has emerged, for instance, that around 12,000 years ago, as the last ice age waned and ice sheets were in full retreat across Europe and North America, the warming abruptly went into reverse. For a thousand years the world returned to the depths of the ice age, only to emerge again with such speed that, as Alley puts it, "roughly half of the entire warming between the ice ages and the postglacial world took place in only a decade." The world warmed by at least 9 degrees-the IPCC's prediction for the next century or so-within ten years. This beggars belief. But Alley and his coresearchers are adamant that the ice cores show this happened.
    Similar switchback temperature changes occurred regularly through the last glaciation, and there were a number of other "flickers" as the planet staggered toward a new postglacial world. Stone Age man, with only the most rudimentary protection from a climatic switchback, must have found that tough. Heaven knows how modern human society would respond to such a change, whereby London would have a North African climate, Mexican temperatures would be visited on New England, and India's billionplus population would be deprived of the monsoon rains that feed them.
    The exact cause of the rise and fall of the ice ages still excites disputes. But it seems that the 100,000-year cycles of ice ages and interglacials that have persisted for around a million years have coincided with a minor wobble in Earth's orbit. Its effect on the solar radiation reaching the planet is minute, and it happens only gradually. But somehow Earth's systems amplify its impact, turning a minor cooling into an abrupt freeze or an equally minor warming into a sudden defrost. The amplification certainly involves greenhouse gases, as Arrhenius long ago surmised. The extraordinary way in which temperatures and carbon dioxide levels have