The View From 1776

Global warming: Our best guess is likely wrong

Computer models fail to substantiate the claimed link between carbon and temperature.

...climate models explain only about half of the heating that occurred during a well-documented period of rapid global warming in Earth’s ancient past….“In a nutshell, theoretical models cannot explain what we observe in the geological record,” said oceanographer Gerald Dickens, a co-author of the study and professor of Earth science at Rice University. “There appears to be something fundamentally wrong with the way temperature and carbon are linked in climate models.”

Posted by .(JavaScript must be enabled to view this email address) on 07/15 at 02:16 PM
  1. Tom,
    You have not grasped the essence of Dr. Dickens' paper. He is saying that the heating in the atmosphere 55 million years ago was more severe than indicated by the CO2 levels would have led us to expect. This in no way invalidates the current work on global warming. Dr. Dickens is considered one of the foremost authorities on the science of global warming. Your understanding of the problem would be increased if you read any of his papers on the topic.
    Posted by .(JavaScript must be enabled to view this email address)  on  07/17  at  05:43 PM
  2. Mr. Jay:

    Try re-reading the report yourself. The point is that none of present-day models (which, by the way, differ from each other, though the matter of man-made global warming is bruited as "settled science") can account for the geological record of warming and CO2 changes.
    Posted by .(JavaScript must be enabled to view this email address)  on  07/17  at  09:34 PM
  3. Mr. Brewton,

    Forgive me for the attached piece because it is a little long, but perhaps it might help you grasp the issue better (New York Times Science article November 23, 1999):

    A gradual warming of unknown cause preceded the sharp upward spike in temperature 55 million years ago, said Miriam E. Katz, a paleooceanographer at Rutgers University, who is the leading author of a report on the ancient phenomenon in the current issue of the journal Science.

    But at some point, the warming crossed a threshold that abruptly kicked the temperature up to a new level, said another author of the Science paper, Dr. Gerald R. Dickens of James Cook University in Australia. He compared it to the stretching of a rubber band: "You gradually pull at both ends and, at some instant, the rubber band suddenly breaks."

    What caused the climate to snap and send the temperature soaring, according to a hypothesis formulated by Dr. Dickens, was a sudden release of methane locked in the ocean floor, touched off by the previous, more gradual warming.

    Methane is a greenhouse gas in its own right, and when released from ocean sediments it also combines with oxygen to form carbon dioxide that eventually percolates to the atmosphere.

    Dr. Dorothy K. Pak of the University of California at Santa Barbara and Dr. Kenneth G. Miller of Rutgers are the other authors of the report in Science, which describes chemical and geological evidence of the ancient rush of greenhouse gases and the way it happened. The evidence was contained in corings and ultrasound readings of sediments on a subsea promontory called the Blake Nose, northeast of Cape Canaveral, Fla.

    The researchers believe that the original, gradual warming, beginning about 60 million years ago, caused a change in ocean circulation currents that pushed warm surface waters down into the deep sea.

    This deep-sea warming converted icelike solid methane locked in crystalline structures in the sea-floor sediments into gaseous form.

    This gas then blasted upward through the sediment, starting mudslides that freed the methane and allowed it to escape into the water and eventually to the atmosphere. On the way, it reacted with oxygen to produce globe-warming carbon dioxide.

    One effect of the warming spike, Ms. Katz says, was to transform the environment of the deep ocean, as evidenced by the extinction of more than half of all species of microscopic bottom-dwelling animals.

    The warming is also believed to have enabled that era's relatively small array of mammals to spread out into formerly frozen regions to colonize other continents, where they proliferated in many evolutionary directions.

    Among these were the ancestors of horses, apes and humans.

    Dr. Dickens has calculated that the sudden influx of carbon associated with the sharp spike of global warming 55 million years ago amounted to at least a billion billion metric tons.

    At present rates of carbon-dioxide emission from global sources, about two-thirds of that amount would be added to the atmosphere by 2100.

    Some scientists say it is possible that before then, some threshold could again be surpassed, resulting in an abrupt but unknown change in climate.

    Many questions remain. The cause of the gradual warming that preceded the spike 55 million years ago is unknown.

    Nor do scientists know the magnitude of the atmospheric concentrations before the gradual warming trend and the spike, frustrating comparisons with today. Moreover, it is not clear how much of the ancient warming resulted from the influx of greenhouse gas and how much from accompanying changes in ocean circulation; Dr. Dickens believes both were involved.

    A further complication, says Dr. Dickens, is that the influx of greenhouse gases was spewed initially into the ocean 55 million years ago, but is going directly into the atmosphere today.

    That difference could affect the rate of the consequent warming, since the ocean's inertia might slow the migration of carbon dioxide into the air, making the ancient warming spike less abrupt than otherwise.

    The evidence drawn from ocean sediments in the new study was not fine-grained enough to determine just how sharp the ancient warming was, Dr. Pak said, though it took place within a few thousand years at most.

    Other large, abrupt climatic changes of the more recent past -- during the transition out of the last ice age, for example -- have taken place within a human lifetime or less and sometimes within a decade, according to recent evidence.

    All of these complications muddy the possible comparison between what happened in the transformational climatic event 55 million years ago and what is happening today. Nevertheless, says Dr. Dickens, the ancient transformation provides a new and continuing opportunity to explore the possible effects of growing concentrations of greenhouse gases without resorting to computer-assisted simulations of the climate.

    And, he says, it teaches that "the earth can, for natural reasons, suddenly change dramatically."
    Posted by .(JavaScript must be enabled to view this email address)  on  07/18  at  03:02 PM
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