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 user 2006-05-17 at 9:46:00 am Views: 64
  • #15470

    Fabled ice field ‘set to vanish’

    A fabled tropical ice field in Africa could disappear in two decades because of climate change, a study says.

    The finding comes from the first survey in a decade of glaciers in the
    Rwenzori Mountains, East Africa, often referred to as the “Mountains of
    the Moon”.

    A British-Ugandan team says an increase in air
    temperature over the last four decades has contributed to a substantial
    reduction in glacial cover.

    Details of the work appear in the journal Geophysical Research Letters.

    Tropical glaciers are very sensitive indicators of tropical climate.
    They indicate quite clearly that the climate is changing

    Richard Taylor, UCL

    The Rwenzori Mountains straddle the border between Democratic Republic of Congo and Uganda.

    They are home to one of four remaining tropical ice fields outside the
    Andes and are renowned for their spectacular and rare plant and animal

    Their legendary status may stretch back to a reference
    by the 2nd Century AD Greek geographer Ptolemy, who wrote of
    snow-capped equatorial peaks that fed the Nile: “The Mountains of the
    Moon whose snows feed the lakes, sources of the Nile”.

    Some researchers think conceptual maps prepared by
    Ptolemy are a good fit for the Rwenzori, which feeds Lake Albert, which
    in turn feeds the White Nile.

    An analysis of data from field surveys and images from
    the LandSat satellites shows the combined area of the Rwenzori glaciers
    has halved from around two sq km to just under one sq km since 1987.

    Weather data collected from field stations shows that
    increased air temperature is the main driver behind the loss of glacial

    Temperature trends

    Trends point to an air temperature rise of roughly half a degree
    Celsius per decade since the 1960s without any significant change in
    annual rainfall.

    Dr Richard Taylor of University College London and
    colleagues extrapolated the data on glacial shrinkage since 1906 and
    found that the glaciers would disappear within 20 years if trends

    “The observed increases of about 0.5C per decade are much greater than
    you would expect,” Dr Taylor told the BBC News website. “You would
    expect, consistent with warming trends for the East African region,
    about 0.1-0.2C per decade.”

    Rainfall data for the region extends back 100 years, but
    temperature records go back no further than the 1960s. Consequently,
    the researchers were unable to say whether they are observing a
    long-term trend.

    There were no field stations higher than 1,800m
    (6,000ft) above sea level, which meant the scientists had to infer
    temperature and rainfall data from information gathered at lower
    altitudes. However, this was relatively straightforward and reliable,
    Dr Taylor explained.

    Loss of cover

    The UCL scientist added: “Tropical glaciers are very sensitive
    indicators of tropical climate. They indicate quite clearly that the
    climate is changing.”

    Local biodiversity is not expected to suffer in the
    short term, but habitats for rare vegetation could be constrained in
    the longer term.

    The largest conglomerations of equatorial ice are in
    the Andes in South America, representing over 90% of glacial cover in
    the tropics.

    Of the four outside the Andes, about two sq km of ice
    remains on Irian Jaya, 0.4 sq km on Mount Kenya, three sq km on
    Kilimanjaro and 0.96 sq km in the Rwenzori.

    The disappearance of the glaciers would have a
    negligible effect on Nile waters, to which the major contribution comes
    from rainfall at lower altitudes.