• Climate changed abruptly at tipping poin

    From ScienceDaily@1:317/3 to All on Tue Nov 16 21:30:38 2021
    Climate changed abruptly at tipping points in past
    Statistical method more accurately determines whether jumps in ice core
    data significant or merely noise.

    Date:
    November 16, 2021
    Source:
    American Institute of Physics
    Summary:
    Climate scientists identify abrupt transitions in climate records
    that may have been caused by the climate system crossing a tipping
    point. They devised a statistical method to determine whether these
    transitions are simply noise or evidence of a more significant
    change. Their method is less error-prone than previous methods,
    since it doesn't rely on human determination. It also allows
    comparing different records consistently and can identify important
    events that may have been overlooked in older studies.



    FULL STORY ========================================================================== Abrupt changes in ice core samples and other records indicate dramatic
    changes in climate occurred at certain points in the past.


    ==========================================================================
    In Chaos, by AIP Publishing, climate scientists identify abrupt
    transitions in climate records that may have been caused by the climate
    system crossing a tipping point. This happens when self-reinforcing
    feedbacks in a system push it away from a stable state, leading to
    dramatic change.

    Identifying these events in the Earth's past is critical to understanding
    the tipping points likely to be encountered this century as a warming
    climate destabilizes the Earth's physical systems and ecosystems.

    The researchers from CNRS (France), UCLA, and Columbia University
    devised a statistical method to determine whether transitions seen in
    climate records such as ice cores are simply noise or evidence of a more significant change.

    This has typically been done by visual inspection, a process that is time- consuming and subjective.

    Their method is less error-prone, since it doesn't rely on human
    determination of whether a jump is a significant transition. It allows comparing different records consistently and can identify important
    events that may have been overlooked in older studies.

    An augmented Kolmogorov-Smirnov (KS) test, a statistical technique
    named after its original authors, provided an alternative approach to recurrence analysis.

    The KS test has been successfully applied to other inherently noisy
    systems, such as finance and signal processing.



    ==========================================================================
    The method compares two samples taken before and after the potential
    transition point to test whether they come from the same continuous distribution. If they don't, the transition point is identified as a significant abrupt change indicative of a true climactic shift.

    "We applied our method to two paleoclimate records of the last climate
    cycle, a Greenland ice core and a speleothem composite record from China,"
    said author Witold Bagniewski.

    Analysis of ice cores reveals that the ratio of two oxygen isotopes varies
    over time. This ratio depends on the local temperature at the time the ice formed, providing a measurement of the climate at that particular time.

    Speleothems are mineral deposits in caves showing a similar pattern of
    isotope ratios varying as the climate changes.

    "Many of the abrupt transitions in the Greenland ice core record
    correspond to shifts between a warmer climate, known as Greenland
    Interstadials (GIs), and a colder climate, the Greenland Stadials (GSs),"
    said Bagniewski.

    The existence of these two climate states, GI and GS, is an example
    of a bistable climate system, in which two distinct states are both
    stable. The climate may jump abruptly from one to the other when crossing
    a tipping point.

    "Our methodology is very effective in correctly detecting abrupt
    transitions in climate records," said Bagniewski. "Its wider application
    may help reconstruct the chronology of Earth's climatic events." ========================================================================== Story Source: Materials provided by American_Institute_of_Physics. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. W. Bagniewski, M. Ghil, D. D. Rousseau. Automatic detection
    of abrupt
    transitions in paleoclimate records. Chaos: An Interdisciplinary
    Journal of Nonlinear Science, 2021; 31 (11): 113129 DOI:
    10.1063/5.0062543 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2021/11/211116111407.htm

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