EARTH SCIENCES: ON THE
DISCOVERY OF RAPID CLIMATE CHANGE
ScienceWeek http://www.scienceweek.com
The following points are made by Spencer Weart (Physics Today
2003 August):
1) How fast can our planet's climate change? Too slowly for humans to
notice, according to the firm belief of most researchers through much of the
20th century. Any shift of weather patterns, even the Dust Bowl droughts
that devastated the
2) In the 1950s, a few researchers found evidence that some of
the great climate shifts in the past had taken
only a few thousand years. During the 1960s and 1970s, other lines of research
made it plausible that the global climate
could shift radically within a few hundred years. In the 1980s and 1990s,
further studies reduced the scale to the span of a single century. Today, there
is evidence that severe change can take less
than a decade. A committee of the National Academy of Sciences (NAS) has called
this reorientation in the thinking of scientists a veritable "paradigm
shift". The new paradigm of abrupt global climate
change, the committee reported in 2002,
"has been well established by research over the last decade, but this new
thinking is little known and scarcely appreciated in the wider community of
natural and social scientists and policy makers."
3) Much earlier in the 20th century, some specialists had
evidence of abrupt climate change in front of
their eyes. The evidence was meaningless to them. To appreciate change occurring within 10 years as significant,
researchers first had to accept the possibility of change
within 100 years. That, in turn, had to wait until they accepted the 1000-year
time scale. The history of this evolution gives a good example of the stepwise
fashion in
which science commonly proceeds, contrary to the familiar heroic myths of
discoveries springing forth in an instant. The history also suggests why, as
the NAS committee worried, most people still fail to realize just how badly the
world's climate might misbehave.
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ON CLIMATE CHANGE
We derive our confidence that the climate
will not change much from its constancy and
generally favorable state in the first half of the
20th century. Before 1920 drought and famine could be counted on to devastate
accordingly. Early in this century Californians expected a truly dry winter
about once in seven years, but for the next 50 years droughts arrived less than
half as often. The 1960s changed all that and the world's climate has returned to an earlier, less benign
state. At the same time rapid population growth and an increasing need for
advance planning in an ever more complex
world keep reducing our capacity for a swift and flexible response.
All this is perfectly normal. During the past two millennia
our climate has changed often, rapidly, and
often drastically. Across
where human subsistence is always marginal, a cold spell in the 14th century
and the Little Ice Age converted the country permanently from a wheat-growing
to a sheep-farming economy, although the temperature fell only 1.5 to 2.0
degrees Celsius.
The cold 14th century also contributed to the demise of the
first European colony west of the
shifted the focus away from the far west of the Viking world administered the
coup de grace.
Not everywhere was the Little Ice Age a bad time. Early in the
19th century, the prairies of
the Little Ice Age arrived together with the new immigrants, who found land and
climate to be far less suitable than promised.
The marked decline in rainfall that followed would have decimated the buffalo
herds, had not the white man taken his toll a little earlier and somewhat more
thoroughly.
Adapted from: Tieerd H. Van Andel: New Views on an Old Planet: A History of Global Change. Cambridge University Press 1994, p.47.
ScienceWeek http://www.scienceweek.com
Best,
Frederick Martin McNeill
Poway, California, United States of America
mmcne...@fuzzysys.com
http://www.fuzzysys.com
http://members.cox.net/fmmcneill/