Global Warming And The Onward March Of The Pine
London - Apr 13, 2004
Climate change could dramatically increase the forest cover of the
Earth's mountains, ecologists are predicting. Using data from the
Austrian Alps, ecologists have developed a model that predicts the area
covered by the local pine, Pinus mugo Turra, will increase from 10% today
to 60% by the turn of the next millennium.
The findings are published in the April issue of the British Ecological
Society's Journal of Ecology and the authors believe that this is the
first paper to model tree line dynamics driven by climate change on a
landscape scale in both time and space.
The Earth's climate has warmed approximately 0.6�C over the past 100
years and the rate of warming looks set to accelerate. Alpine tree lines
are assumed to be particularly sensitive to climate change, with high
mountain forests predicted to shift their ranges up-slope at the expense
of alpine vegetation.
According to one of the authors, Dr Stefan Dullinger of the University of
Vienna, "Shrinkage and fragmentation of alpine habitats, as a
consequence, may pose a serious threat to populations of many alpine
plants, especially to regional endemics.
On the other hand, expansion of mountain forests may also improve certain
ecosystem services for human welfare, such as erosion control and
increased water holding capacity in many high mountain water catchments."
Dr Dullinger says that the findings will help the City of Vienna use
pines to protect its drinking water catchment from erosion and pollution.
However, he warns that the Viennese model is not easily transferable to
other tree line systems.
"Tree lines may respond quite idiosyncratically to global warming. Our
model highlights the complex interactions of temperature rise, species
specific traits and resident alpine vegetation cover in driving a
possible future tree line expansion," said Dullinger.
Climate: Unraveling the borehole riddle
By Dan Whipple
Boulder (UPI) April 12, 2004
Progress in the genuine understanding of climate change, as with all
science, is achieved through the accumulation of detail and, in some
cases, excruciating detail.
Case in point: geologic boreholes.
In order to understand whether the modern climate warming is exceptional,
scientists must learn how the planet's atmosphere behaved in the past.
This is a complex task. Few temperature records go back more than two
centuries or so, and most of what does exist tends to be concentrated in
particular regions. For instance, there are thermometer measurements for
the 19th century for North America and Europe, but virtually none for
anywhere in the Southern Hemisphere.
The problem of determining a global average temperature, even today --
never mind past millennia -- is further complicated by the fact that
two-thirds of the Earth is covered by oceans, which until very recently
had no current thermometry records and few ways of obtaining historical
Scientists from various disciplines have devised clever ways to overcome
this lack of data. They have relied on so-called proxy records, which can
provide a great deal of information, albeit indirectly. As a result, each
one, by definition, has limitations and each one has generated a
controversy about its interpretation.
To reconstruct Earth's climate, scientists have looked at a number of
proxy records, such as tree rings. They contain potential temperature and
precipitation data that can be preserved in fossilized remnants as well
as living trees.
Climate researchers also have examined coral reefs, whose growth varies
with water temperature. They have studied ocean sediments, from which
oxygen isotope contents can infer temperature. They have extracted ice
cores, which trap oxygen and hydrogen and can provide a proxy for
temperature records. They have calculated glacier movements, which
advance and retreat depending on temperature.
They also have drilled boreholes -- core samples extracted from soil and
rock instead of ice -- to attempt to determine how climatic processes
have transferred surface heat to the underground environment.
Although all of these proxy records have drawn reactions ranging from
differing interpretations to outright disagreement, a recent exchange
over boreholes demonstrates how the details of climate science can affect
very large conclusions about the warming Earth.
Gavin Schmidt, of the NASA Goddard Institute for Space Studies and
Climate Systems Research at Columbia University in New York, and Michael
Mann, of the Department of Environmental Sciences at University of
Virginia in Charlottesville, published a paper recently in the journal
Geophysical Research Letters that argued snow cover affected and perhaps
skewed the borehole record.
"Our paper wasn't that fundamental," Schmidt told United Press
International. "I'm not going to claim that it was groundbreaking work.
Changes in snow cover can affect the temperatures that get transmitted to
deep boreholes. You're not going to find anybody who is going to disagree
As it turns out, some geologists are taking exception, including David
Chapman, Marshall Bartlett and Robert Harris, all of the Department of
Geology and Geophysics at the University of Utah in Salt Lake City.
In a comment published in GRL, Chapman and the others argued: "We have
been working on the same question as Mann and Schmidt -- the fidelity of
ground surface temperature and surface air tracking, in particular the
effect of seasonal snow cover ... But our analysis, based not on model
simulation but analysis of measurements of GST and SAT at observatories
... leads us to very different conclusions."
The most important point, Bartlett told UPI, "is that there is a
difference between the inferred amount of warming that has occurred. We
have confidence that the physics is really well understood. Any change in
the surface temperature gets conducted to the solid rock."
The interpretation resulting from these differences could be substantial.
Bartlett said the borehole records show warming to be about twice as
large since the advent of the industrial age as other estimates. He also
noted the trio's results "indicate that the warming induced by
industrialization since 1750 is more than we see in the proxy records and
agrees with the surface air temperature records."
This seemingly technical matter attracted the attention of Harvard
University astrophysicist Willie Soon, a controversial figure among
climate scientists, who argues that modern warming is not exceptional in
the historic period and the so-called medieval warm period -- from about
800 to 1300 A.D. -- was warmer than today. Soon is also a senior
scientist at the George Marshall Institute in Washington, D.C., one of
the leading skeptical think tanks on climate.
Soon e-mailed the analyses by Schmidt and Mann and by Chapman, Bartlett
and Harris to journalists with a brief note: "Just in case it is of
interest." What apparently attracted his attention was not the technical
arguments so much as the fact Mann was one of the co-authors. Mann's work
on modern temperature increases was cited by the Intergovernmental Panel
on Climate Change's 2001 assessment on global warming.
"Michael Mann has become a lightning rod for everybody and their dog,"
Schmidt said. "It's a ridiculous tactic. Obviously, you know why they do
it. Mike has been getting the same thing ever since that assessment
report. He's a combative guy. He likes to carry ball to the opposition.
"I work in a modeling group," Schmidt added. "I don't have any particular
axes to grind. General climate model experiments give you a laboratory to
test different things. You make things change with respect to solar
forcing, to greenhouse gases. To what extent does this model reflect the
Schmidt explained that because snow cover in Eurasia actually has
increased over the last few decades.
"It's a very complicated story and involves four dynamics of climate.
There isn't going to be a 'gotcha' moment, when everything is going to be
clear, where you get the temperature for the middle of the Little Ice
Age," he said.
Dan Whipple covers the environment for UPI Science News. E-mail
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