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Climate Has History Of Fast Changes

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  • Pat Neuman, Hydrologist
    by Dan Whipple Boulder (UPI) Mar 09, 2004 Those who think global climate change requires many years to unfold might want to take note of other worldwide
    Message 1 of 1 , Mar 9 10:17 AM
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      by Dan Whipple
      Boulder (UPI) Mar 09, 2004
      Those who think global climate change requires many years to unfold might want
      to take note of other worldwide temperature alterations in the past 15,000
      years, which occurred, in geological terms, quick as a flash.
      "Climate has changed abruptly in the past," said Carrie Morrill, a
      postdoctoral fellow at the National Center for Atmospheric Research who has just
      completed a paper on the subject.

      For example, Morrill explained, there was a 14 degree Fahrenheit rise at the end
      of a period called the Younger Dryas -- a climate period that occurred nearly
      12,000 years ago, just after the last ice age ended. While scientists are
      worried about the potential impact of a 2 degree or 3 degree F. global increase
      over the next century, the 14 degree rise occurred "in a period of
      decades," she said. "Future climate change probably won't be
      gradual."

      Concerns about a possible lightning-like climate shift are beginning to emerge
      from a number of quarters, including some surprising sources. For example, a new
      Pentagon report speaks of temperature rises overwhelming the world's
      infrastructure over the next 20 years, causing flooding, energy shortages,
      drought, famine and rioting.

      Nations might mass troops on their borders, threaten neighbors, and even wage
      nuclear war as they attempted to deal with the severe upheavals in their
      environments and economies, the report states.

      The report, "An Abrupt Climate Change Scenario And Its Implications For
      United States National Security," characterizes these possibilities as
      remote but "plausible."

      The idea of such a rapid shift in climate -- from moderate to glacial or the
      reverse in only a decade or two -- seem's counterintuitive. But there is little
      doubt it has happened in the past.

      Two events have been particularly well studied. They occurred at the beginning
      and end of the Younger Dryas. About 11,600 years ago, there was a rapid drop in
      temperature, followed about 1,000 years later by an equally rapid increase.

      Then about 8,200 years ago, there was a another rapid change -- another
      temperature decline. This occurrence, called the 8ka event, has been especially
      well documented. Average temperatures, as computed from data derived from
      Greenland ice cores, fell nearly 11 degrees F. in a few decades.

      Moreover, this dramatic temperature change was not restricted to the Arctic, or
      even to the northern hemisphere. Paleoclimate records for Venezuela show a
      virtually identical pattern for both time and temperature, as do global proxy
      records. All indications are that the the 8ka event was global, steep and
      rapid.

      MOrrill examined 105 different proxy records that can be used to track climate
      conditions covering about the last 15,000 years. These records include data
      collected from ice cores, marine sediments, lake sediments and fossils such as
      ostracods that demonstrate the impact of climate over time. Because of the wide
      range of records, she was able to narrow the time focus of the data to 150 year
      increments or better.

      Her analysis shows two new periods of abrupt climate change -- one occurring
      5,500 years to 5,800 years ago, and the other from 4,000 years to 4,800 years
      ago. During both periods, the climate in the tropics became drier; in the
      Mediterranean, colder and drier; in the high latitudes, colder, and in the
      mid-latitudes, colder and wetter.

      "Technically, an abrupt climate change occurs when the climate system is
      forced to cross some threshold, triggering a transition to a new state at a rate
      determined by the climate system itself and faSter than the cause,"
      according to a definition developed by the National Research Council.

      Abrupt change needs a trigger, an amplifier -- some mechanism to have the
      trigger affect a large area -- and a source of persistence. It turns out lots of
      triggers have been identified, for example, an accumulation of carbon dioxide in
      the atmosphere, as is occurring now.

      A paper in Science in March 2003 by Penn State glaciologist Richard Alley and
      others, noted: "... the drying of the Sahara during the latter part of the
      Holocene, and the ice age ... oscillations, are linked in time and
      mechanistically to orbital forcing. The Sahara dried as the African monsoon
      weakened in response to reductions in summertime incoming solar radiation ...
      Triggers may be fast (e.g., outburst floods from glacier-dammed lakes), slow
      (continental drift, orbital forcing) or somewhere between (human-produced
      greenhouse gases) and may even be chaotic; multiple triggers aLso may
      contribute."

      Although potential triggers for abrupt climate change have been fairly well
      identified, mechanisms that can spread the impacts globally are less obvious.

      "Global circulation models, forced by hypothesized causes of abrupt climate
      changes, often simulate some regional changes rather well, underestimate others,
      and fail to generate sufficiently widespread anomaly patterns," according
      to the paper by Alley et al.

      In her research, Morrill looked at the possibility the El Ni�o-Southern
      Oscillation phenomenon could serve as a globalizer for temperature changes in
      the tropics. El Ni�os, which are triggered by changes in tropical Pacific Ocean
      sea surface temperatures, are known to affect climate across North and South
      America, and perhaps even parts of Europe.

      The results seem inconclusive, however, at least as they relate to the rapid
      climate changes Morrill identified during the Holocene. She found the El Ni�o
      was stronger at the last glacial maximum -- about 21,000 years ago -- weaker
      during the mid-Holocene, and stronger now.

      Whatever the scientific uncertainties, rapid climate change is about to hit
      popular culture. The film "The Day After Tomorrow" is scheduled to be
      released in May. It depicts rapid climate change -- from the trailers,
      apparently in the matter of days, not decades -- that causes tidal waves to
      sweep over Manhattan and turns all that sea water into glaciers.

      "Most ecological and economic systems have the ability to adapt to a
      changing environment," the Science paper said. "Slower changes allow
      response with less disruption in both ecosystems and economies. Abrupt changes
      are particularly harmful where the individual entities have long lifetimes or
      are relatively immobile; damages also increase with the abruptness and
      unpredictability of the climate change and are likely to be larger if the system
      is Unmanaged."

      Long-lived and relatively immobile unmanaged ecosystems such as mature forests
      and coral reefs thus are likely to be especially sensitive to climate change,
      the paper continued. "Specific attention to vulnerable sectors such as
      these is warranted," its authors wrote.
      http://www.spacedaily.com/news/climate-04k.html
      All rights reserved. Copyright 2004 by United Press International.

      Scientist Muzzled Over Global Warming
      London (UPI) Mar 09, 2004 - The British scientist who claimed global warming is
      more of a danger than terrorism has been rebuked by the government, The
      Independent reported Monday.
      David King was given the hush order by Ivan Rogers, Prime Minister Tony Blair's
      principal private secretary, who told the leader's chief scientific adviser to
      limit his contact with the media.

      King wrote a scathing article in the American journal Science in January
      attacking President George Bush's administration for failing to take climate
      change seriously.

      "In my view, climate change is the most severe problem we are facing today,
      more serious even than the threat of terrorism," he wrote.

      In a leaked memo, King was told by Rogers, "This sort of discussion does
      not help us achieve our wider policy aims ahead of our G8 presidency (next
      year)."

      The newspaper said when asked toExplain how he had come to the conclusion that
      global warming was more serious than terrorism, King replied his equation was
      "based on the number of fatalities that have already occurred,"
      implying global warming has already killed more people than terrorism.







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