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]]]]]]]]]] HAS THE GLOBE REALLY WARMED? [[[[[[[[[[[[
(11/21/89)
[From Technology Review 92(8):80 (November/December 1989)]
[Kindly uploaded by Freeman 10602PANC]
Since the mid-nineteenth century, merchant-marine captains of
all nations have been required to log air and water temperatures
every six hours for weather services such as the British
Meteorological Office. Crews on each watch have hauled water
from the sea in standard buckets, dipped in standard
thermometers, recorded the data, and, generally, radioed it back.
The result is an incredible storehouse of information about
global temperatures since the Industrial Revolution.
Reginald E. Newell, Jane Hsiung, and Wu Zhongxiang of MIT,
along with colleagues from the ``British Met,'' as they call it,
have collected and analyzed these data. MIT Press intends to
publish them in the Global Ocean Surface Temperature Atlas. One
of the most striking results suggested by the data is that there
appears to have been little or no global warming over the past
century.
The advantage of ocean readings is that they are not
contaminated by urbanization: the growth of structures and roads
even in the small towns where many weather stations are located
can raise temperatures, Newell explains. Unfortunately, ocean
readings are not entirely reliable either. One of the chief
problems is that prior to World War II, the buckets for
collecting water were made of canvas. As it was hauled onto the
deck, the water could be cooled by wind and heated by sun.
Christopher Folland of the British Meteorological Office and Jane
Hsiung attempted to correct for such problems, for example by
measuring the cooling of the buckets at different wind speeds.
Gauging long-term temperature change required more analysis.
First, Newell, Hsiung, and Wu needed to measure the cooling
caused when volcanoes inject dust and gases into the atmosphere.
They discovered an intriguing piece of work that measures the
atmospheric ``turbidity'' from the dust over the past century.
Beginning in the late 1800s, weather stations have used devices
known as Campbell-Stokes sunshine recorders that burn a track in
a paper card each day, indicating how long the sun was up.
Researchers at the University of Mainz in West Germany collected
and analyzed numerous such cards, noting particularly the
beginning and end of the burn, which correspond to sunrise and
sunset. Whenever atmospheric turbidity rose, the burn started
later and ended earlier. The weather station in Sonnblick,
Austria, almost unaffected by urban pollution at an elevation of
3 kilometers in the Alps, provides a record of turbidity back to
1887.
Newell, Hsiung, and Wu also assessed the periodic change in
tropical temperatures caused by the El Ni$o-Southern Oscillation,
a complex of ocean and air currents. Factoring out the effects
of the El Ni$o-Southern Oscillation and the cooling caused by
volcanoes, they found that global temperatures have warmed by
only 0.2xC over the past century, which is within the estimated
margin of error. In other words, the results leave open the
possibility that there has been no warming at all.
In a paper based on the same data in Geophysical Research
Letters, Nicholas E. Newell (Reginald Newell's son) joins the
other researchers to examine a third temperature variation: a
roughly 22-year cycle of warming and cooling that has occurred
since 1856, when the marine data begin. This may be caused by
the 22-year solar magnetic cycle, during which the sun's magnetic
field changes polarity and then returns to its original state.
The magnetic cycle is reflected in changing sunspot patterns.
When the authors subtract from the basic temperature record all
cycles of less than 26 years -- the chief one being this 22-year
warming-and-cooling pattern -- they find ``no appreciable
difference'' between temperatures in 1856 and 1986.
Both studies are at odds with some other research. For
example, using land data that attempt to factor out effects of
urbanization, James Hansen of NASA Goddard Space Flight Center
and Sergej Lebedeff of Sigma Data Services Corp. conclude that
the globe has warmed 0.5 degrees C to 0.7 degrees C over the past
century.
The conflict is far from resolved. Unfortunately, despite all
the models of how global climate may change, there is relatively
little funding for research on the actual record. A case in
point: though the Global Ocean Surface Temperature Atlas has
passed peer review and been accepted by MIT Press, so far no
sponsor has been willing to provide the modest subsidy that such
a technical book often requires for publication -- it this case
$60,000.
* * *
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