Date: Tue Jul 01 2003 - 07:45:52 PDT

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    Eurekalert, 28 June 2003

    Celestial Driver of Phanerozoic Climate?

    Nir J. Shaviv, Racah Institute of Physics, Hebrew University of
    Jerusalem, Jerusalem, 91904, Israel, and JŠn Veizer, Institut fŁr
    Geologie, Mineralogie und Geophysik, Ruhr Universitšt, 44780 Bochum,
    Germany, and Ottawa-Carleton Geoscience Centre, University of Ottawa,
    Ottawa, ON K1N 6N5, Canada.

    Is there a link between the climate on planet Earth and celestial
    processes associated with solar activity, supernovas ands spiral
    galaxies? In a uniquely cross-disciplinary approach to this problem, Nir
    Shaviv, an astrophysicist at Racah Institute of Physics (Hebrew
    University, Israel) and Jan Veizer a geochemist at the University of
    Ottawa (Canada) and Ruhr University (Germany), have collaborated to
    address this question from the perspective of astrophysics and geology.
    In this paper, the authors examined the periodicity in the Earth's
    climate over the past 600 m.y. that is apparent from the analysis of
    isotopes of oxygen in fossil material. This was compared to the
    periodicity predicted in the variation in the flux of cosmic rays (CRF)
    reaching the Earth (and observed in the CRF recorded in iron meteorites)
    as a function of the periodic passage of our solar system through the
    spiral arms of the Milky Way. Cosmic rays are interpreted to influence
    cloud formation on our planet and hence affect the planetary albedo. The
    authors demonstrate a tantalizing correlation between celestial and
    geological processes and add to the proposition that celestial processes
    may be an important, perhaps even dominant influence, on climate change.
    If this is the case, then the role of carbon dioxide becomes even more
    critical to understand as it may well amplify the signals forced by
    celestial processes. This is one of a number of new studies that are
    shaking up our traditional understanding of the link between climate and
    atmospheric gases.


    GSA Today, 1 July 2003

    Celestial driver of Phanerozoic climate?

    Nir J.Shaviv, Racah Institute of Physics,Hebrew University of
    Jerusalem,Jerusalem, 91904, Israel
    JŠn Veizer, Institut fŁr Geologie,Mineralogie und Geophysik,Ruhr
    Universitšt, 44780 Bochum, Germany, and Ottawa-Carleton Geoscience
    Centre, University of Ottawa, Ottawa,Ontario K1N 6N5,Canada

    Atmospheric levels of CO2 are commonly assumed to be a main driver of
    global climate. Independent empirical evidence suggests that the
    galactic cosmic ray flux (CRF) is linked to climate variability. Both
    drivers are presently discussed in the context of daily to millennial
    variations, although they should also operate over geological time
    scales. Here we analyze the reconstructed seawater paleotemperature
    record for the Phanerozoic (past 545 m.y.), and compare it with the
    variable CRF reaching Earth and with the reconstructed partial pressure
    of atmospheric CO2 (pCO2 ). We find that at least 66% of the variance in
    the paleotemperature trend could be attributed to CRF variations likely
    due to solar system passages through the spiral arms of the galaxy.
    Assuming that the entire residual variance in temperature is due solely
    to the CO2 greenhouse effect, we propose a tentative upper limit to the
    long-term "equilibrium" warming effect of CO2, one which is potentially
    lower than that based on general circulation models.



    The Guardian, 1 July 2003,3604,988380,00.html

    Shadow of extinction: Only six degrees separate our world from the
    cataclysmic end of an ancient era

    George Monbiot

    It is old news, I admit. Two hundred and fifty-one million years old, to
    be precise. But the story of what happened then, which has now been told
    for the first time, demands our urgent attention. Its implications are
    more profound than anything taking place in Iraq, or Washington, or even
    (and I am sorry to burst your bubble) Wimbledon. Unless we understand
    what happened, and act upon that intelligence, prehistory may very soon
    repeat itself, not as tragedy, but as catastrophe.

    The events that brought the Permian period (between 286m and 251m years
    ago) to an end could not be clearly determined until the mapping of the
    key geological sequences had been completed. Until recently,
    palaeontologists had assumed that the changes that took place then were
    gradual and piecemeal. But three years ago a precise date for the end of
    the period was established, which enabled geologists to draw direct
    comparisons between the rocks laid down at that time in different parts
    of the world.

    Having done so, they made a shattering discovery. In China, South
    Africa, Australia, Greenland, Russia and Svalbard, the rocks record an
    almost identical sequence of events, taking place not gradually, but
    relatively instantaneously. They show that a cataclysm caused by natural
    processes almost brought life on earth to an end. They also suggest that
    a set of human activities that threatens to replicate those processes
    could exert the same effect, within the lifetimes of some of those who
    are on earth today.

    As the professor of palaeontology Michael Benton records in his new
    book, When Life Nearly Died, the marine sediments deposited at the end
    of the Permian period record two sudden changes. The first is that the
    red or green or grey rock laid down in the presence of oxygen is
    suddenly replaced by black muds of the kind deposited when oxygen is
    absent. At the same time, an instant shift in the ratio of the isotopes
    (alternative forms) of carbon within the rocks suggests a spectacular
    change in the concentration of atmospheric gases.

    On land, another dramatic transition has been dated to precisely the
    same time. In Russia and South Africa, gently deposited mudstones and
    limestones suddenly give way to massive dumps of pebbles and boulders.
    But the geological changes are minor in comparison with what happened to
    the animals and plants.

    The Permian was one of the most biologically diverse periods in the
    earth's history. Herbivorous reptiles the size of rhinos were hunted
    through forests of tree ferns and flowering trees by sabre-toothed
    predators. At sea, massive coral reefs accumulated, among which lived
    great sharks, fish of all kinds and hundreds of species of shell

    Then suddenly there is almost nothing. The fossil record very nearly
    stops dead. The reefs die instantly, and do not reappear on earth for 10
    million years. All the large and medium-sized sharks disappear, most of
    the shell species, and even the great majority of the toughest and most
    numerous organisms in the sea, the plankton. Among many classes of
    marine animals, the only survivors were those adapted to the
    near-absence of oxygen.

    On land, the shift was even more severe. Plant life was almost
    eliminated from the earth's surface. The four-footed animals, the
    category to which humans belong, were nearly exterminated: so far only
    two fossil reptile species have been found anywhere on earth that
    survived the end of the Permian. The world's surface came to be
    dominated by just one of these, an animal a bit like a pig. It became
    ubiquitous because nothing else was left to compete with it or to prey
    upon it.

    Altogether, Benton shows, some 90% of the earth's species appear to have
    been wiped out: this represents by far the gravest of the mass
    extinctions. The world's "productivity" (the total mass of biological
    matter) collapsed.

    Ecosystems recovered very slowly. No coral reefs have been found
    anywhere on earth in the rocks laid down over the following 10 million
    years. One hundred and fifty million years elapsed before the world once
    again became as biodiverse as in the Permian.

    So what happened? Some scientists have argued that the mass extinction
    was caused by a meteorite. But the evidence they put forward has been
    undermined by further studies. There is a more persuasive case for a
    different explanation. For many years, geologists have been aware that
    at some point during or after the Permian there was a series of gigantic
    volcanic eruptions in Siberia. The lava was dated properly for the first
    time in the early 1990s. We now know that the principal explosions took
    place 251 million years ago, precisely at the point at which life was
    almost extinguished.

    The volcanoes produced two gases: sulphur dioxide and carbon dioxide.
    The sulphur and other effusions caused acid rain, but would have bled
    from the atmosphere quite quickly. The carbon dioxide, on the other
    hand, would have persisted. By enhancing the greenhouse effect, it
    appears to have warmed the world sufficiently to have destabilised the
    superconcentrated frozen gas called methane hydrate, locked in sediments
    around the polar seas. The release of methane into the atmosphere
    explains the sudden shift in carbon isotopes.

    Methane is an even more powerful greenhouse gas than carbon dioxide. The
    result of its release was runaway global warming: a rise in temperature
    led to changes that raised the temperature further, and so on. The
    warming appears, alongside the acid rain, to have killed the plants.
    Starvation then killed the animals.

    Global warming also seems to explain the geological changes. If the
    temperature of the surface waters near the poles increases, the
    circulation of marine currents slows down, which means that the ocean
    floor is deprived of oxygen. As the plants on land died, their roots
    would cease to hold together the soil and loose rock, with the result
    that erosion rates would have greatly increased.

    So how much warming took place? A sharp change in the ratio of the
    isotopes of oxygen permits us to reply with some precision: 6C. Benton
    does not make the obvious point, but another author, the climate change
    specialist Mark Lynas, does. Six degrees is the upper estimate produced
    by the UN's scientific body, the intergovernmental panel on climate
    change (IPCC), for global warming by 2100. A conference of some of the
    world's leading atmospheric scientists in Berlin last month concluded
    that the IPCC's model may have underestimated the problem: the upper
    limit, they now suggest, should range between 7 and 10 degrees. Neither
    model takes into account the possibility of a partial melting of the
    methane hydrate still present in vast quantities around the fringes of
    the polar seas.

    Suddenly, the events of a quarter of a billion years ago begin to look
    very topical indeed. One of the possible endings of the human story has
    already been told. Our principal political effort must now be to ensure
    that it does not become set in stone.

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