PLEASE NOTE:
*
CCNet CLIMATE SCARES & CLIMATE CHANGE, 14 March 2001
----------------------------------------------------
"At the beginning of the Little Ice Age, some 90 percent of
Europe's
population consisted of peasants engaged in subsistence farming.
Everyone, including the nobility, was dependent upon good weather
and bountiful harvests. Two bad years in a row and people started
to die.
As the Little Ice Age's unstable weather continued, however,
farmers began
to adapt. Innovations began in the Low Countries and spread to
England, including the introduction of new methods, new crops and
the
decline of subsistence farming on small plots in favor of
commercial
farming on larger tracts. This brought about a degree of
prosperity, making
England, for example, not only self-sufficient but also able to
export
grain. It also contributed to the growth of cities. France,
however, did
not adopt new farming techniques. The result, in the bad weather
of
the 18th Century, was widespread hunger. Peasants flooded into
Paris
demanding bread, contributing mightily to the political unrest
that
eventually brought down the monarchy and began the French
Revolution."
--Chauncey Mabe, Chicago Tribune, 12 March 2001
"It is interesting to note that in this region of the world,
where
climate models predict large increases in temperature as a result
of the
historical rise in the air's CO2 concentration, real-world data
show
an actual cooling trend since around 1940, when the greenhouse
effect of
CO2 should have been most prevalent. And, where warming does
exist in the
record (between about 1820 and 1940), much of it correlates with
changes in
solar irradiance and volcanic activity - two factors definitely
free of
anthropogenic influence. Have the climate alarmists try
explaining
that one to you!"
--Center for the Study of Carbon Dioxide and Global Change,
14 March 2001
(1) A LUNAR-CLIMATE LINK?
CO2 Science, 14 March 2001
(2) RAPID CLIMATE CHANGE IN CHINA: A COMMON OCCURANCE
CO2 Science, 14 March 2001
(3) HISTORICAL TALES OF HOW HUMANITY WEATHERED CHANGES IN CLIMATE
Chicago Tribune, 12 March 2001
(4) CLIMATE CHANGE IN THE ASIAN SUBARCTIC
CO2 Science, 14 March 2001
(5) URBANIZATION EFFECTS OF TEMPERATURE MESSUREMENTS
CO2 Science, 14 March 2001
(6) ELEVATED CO2 CONCENTATIONS ON WATER USE EFFICIENCY
CO2 Science, 1`4 March 2001
(7) MAJOR STUDIES JEOPARDIZE IPCC STORYLINES
Environmental News Network, 10 March 2001
(8) ARCTIC SEA ICE THICKNESS REMAINED CONSTANT DURING THE 1990s
John L Daly, 12 March 2001
(9) GLOBAL WARMING QUESTIONED
The Observer India, 22 January 2001
(10) LITTLE ICE AGE A GLOBAL EVENT
Greening Earth Society, 6 March 2001
(11) MORE EVIDENCE FOR THE GLOBAL EXTENT OF THE LITTLE ICE AGE
CO2 Science, 7 March 2001
==============
(1) A LUNAR-CLIMATE LINK?
From CO2 Science, 14 March 2001
http://www.co2science.org/journal/2001/v4n11c2.htm
Reference
Cerveny, R.S. and Shaffer, J.A. 2001. The moon and El
Niño. Geophysical
Research Letters 28: 25-28.
Background
A lack of understanding of the physical forcing mechanism(s)
driving ENSO is
perhaps one reason why climate alarmists are quick to claim that
CO2-induced
global warming will increase the frequency and magnitude of ENSO
events.
Such claims, however, as we have reported previously, are not
supported by
the observational record (see our Subject Index headings ENSO,
ENSO -
Summary). We now report the results of an intriguing study
that
hypothesizes a natural forcing of ENSO by lunar tidal forces.
What was done
The authors examined the possibility that lunar tidal forces act
as an
external forcing mechanism in regulating sea surface temperatures
tied to
ENSO events.
What was learned
A statistically significant correlation was found between maximum
lunar
declination (MLD) and both equatorial Pacific sea surface
temperatures and
South Pacific atmospheric pressure (the Southern Oscillation
Index) over the
period 1854 to 1999. High MLDs were associated with La Niña
conditions,
while low MLDs were associated with El Niño conditions. Under
high MLD,
circulation in the Pacific gyre is enhanced by tidal forces,
inducing
cold-water advection into the equatorial region that is
characteristic of La
Niña conditions. Under low MLD, on the other hand, tidal forcing
is
weakened, cold water advection is reduced, and warmer sea surface
conditions
characteristic of El Niño prevail.
What it means
The importance of lunar forcing on climate appears to be gaining
momentum in
climate change discussions (see Lunar Tides and Climate Change).
However,
the authors readily acknowledge that while ENSO events appear to
be
"substantially associated with MLD," they correctly
note that "other factors
must still be considered and investigated." Projecting the
relationships
they developed into the future, the authors find that MLD is
currently
increasing and will continue to do so over the next several
years,
indicating "a greater potential for the occurrence of colder
SSTs in the
equatorial Pacific, or non-El Niño (either La Niña or neutral)
conditions."
Copyright © 2001. Center for the Study of Carbon Dioxide and
Global Change
===========
(2) RAPID CLIMATE CHANGE IN CHINA: A COMMON OCCURANCE
From CO2 Science, 14 March 2001
http://www.co2science.org/journal/2001/v4n11c3.htm
Reference
Yafeng, S., Tandong, Y. and Bao, Y. 1999. Decadal climatic
variations
recorded in Guliya ice core and comparison with the historical
documentary
data from East China during the last 2000 years. Science in
China Series
D-Earth Sciences 42 Supp.: 91-100.
What was done
The authors analyzed high-resolution records of delta18 obtained
from the
Guliya ice cap (35.2°N, 81.5°E, 6200 m a.s.l.) located in the
Qinghai-Tibet
Plateau of China as a proxy for temperature in that region of the
world over
the past 2000 years. A precipitation record was also constructed
for this
time period based upon a model analysis of annual snowfall
accumulation
rates.
What was learned
Prior to AD 270, climatic conditions were characterized as
relatively warm
and wet, followed by a cold and dry period that lasted until
around 970 AD.
A moderately warm and dry period dominated the climate between
970 and 1510
AD, after which conditions deteriorated into a "well-defined
'Little Ice
Age'" that lasted until around 1930.
Perhaps the most striking discovery reported in this paper is the
authors'
finding that there have been 33 abrupt climatic shifts on the
order of 3°C
that took place over the course of two or three decades over the
past 2000
years. Furthermore, among these 33 abrupt transitions, there have
been
"several large ones," including a 7°C decrease between
250 and 280 AD and a
7°C increase between 550 and 580 AD. Another 7°C increase was
seen over the
longer time interval between 1120 and 1260 AD, corresponding to
the Medieval
Warm Period.
What it means
The results of this paper clearly demonstrate a dynamic feature
of earth's
climate system that is totally independent of human activities,
while at the
same time revealing the reality of both the Medieval Warm Period
and the
Little Ice Age, in yet another rebuff of the climate alarmist
claim that
both of these climatic excursions are but figments of people's
imaginations.
Thank goodness for real-world data!
Copyright © 2001. Center for the Study of Carbon Dioxide
and Global Change
===========
(3) HISTORICAL TALES OF HOW HUMANITY WEATHERED CHANGES IN CLIMATE
From Chicago Tribune, 12 March 2001
http://www.chicagotribune.com/leisure/tempo/printedition/article/0,2669,SAV-0103120224,FF.html
By Chauncey Mabe
How Climate Made History, 1300-1850
By Brian Fagan
Basic Books, 246 pages, $26
In 1694, the Barony of Culbin prospered in coastal northeastern
Scotland. A
collection of farms on 1,400 valuable hectares, it produced
wheat, barley,
oats and salmon, keeping the family of Laird Alexander Kinnaird
living
comfortably in their rural mansion. Then, in early November,
while farm
workers were in the fields gathering the late barley crop, a
north or
northwesterly gale brought ferocious winds in off the North Sea.
Thirty hours later, the entire barony -- 16 farms -- had been
buried under
loose sand blown in from the coastal dunes. "A rich estate
had become a
desert overnight," writes Brian Fagan. "Laird Alexander
was transformed from
a man of property to a pauper in a few hours and was obliged to
petition
Parliament for exemption from land taxes and protection from his
creditors.
He died brokenhearted three years later."
The tragedy of Culbin, one of countless obscure historical
anecdotes
recounted in Fagan's "The Little Ice Age," is a
dramatic example of the
power of climate to alter the course of human life, from the
individual
scale to the fate of nations and continents.
"We need to understand just how profoundly the climatic
events of the Little
Ice Age rippled through Europe over five hundred momentous years
of
history," writes Fagan. "These events did more than
help shape the modern
world. They are the easily ignored, but deeply important, context
for the
unprecedented global warming today. They offer precedent as we
look into the
climatic future."
"The Little Ice Age," a period of violent shifts in
weather, began about
1300 A.D. and gradually came to an end from 1850 to the present.
Fagan shows
how the long Medieval Warm Period (900-1200), with its mild
winters, warm
summers and regular harvests, supported the stability of the
feudal system
that dominated Europe.
It also enabled the Vikings to settle Iceland and Greenland, and
to sail
westward to North America in search of timber, fish and other
commodities.
If you've ever wondered why the Vikings failed to establish
permanent
settlements in North America, Fagan offers the answer:
"As the Arctic ice pack spread southward, Norse voyages to
the west were
rerouted into the open Atlantic, then ended altogether.
Storminess increased
in the North Atlantic and North Sea. Colder, much wetter weather
descended
on Europe between 1315 and 1319, when thousands perished in a
continent-wide
famine."
At the beginning of the Little Ice Age, some 90 percent of
Europe's
population consisted of peasants engaged in subsistence farming.
Everyone,
including the nobility, was dependent upon good weather and
bountiful
harvests. Two bad years in a row and people started to die. As
the Little
Ice Age's unstable weather continued, however, farmers began to
adapt.
Innovations began in the Low Countries and spread to England,
including the
introduction of new methods, new crops and the decline of
subsistence
farming on small plots in favor of commercial farming on larger
tracts. This
brought about a degree of prosperity, making England, for
example, not only
self-sufficient but also able to export grain. It also
contributed to the
growth of cities.
France, however, did not adopt new farming techniques. The
result, in the
bad weather of the 18th Century, was widespread hunger. Peasants
flooded
into Paris demanding bread, contributing mightily to the
political unrest
that eventually brought down the monarchy and began the French
Revolution.
Copyright 2001, Chicago Tribune
==========
(4) CLIMATE CHANGE IN THE ASIAN SUBARCTIC
From CO2 Science, 14 March 2001
http://www.co2science.org/journal/2001/v4n11c1.htm
Reference
Vaganov, E.A., Briffa, K.R., Naurzbaev, M.M., Schweingruber,
F.H., Shiyatov,
S.G. and Shishov, V.V. 2000. Long-term climatic changes in the
arctic region
of the Northern Hemisphere. Doklady Earth Sciences 375:
1314-1317.
What was done
Using tree-ring width as a proxy for temperature, the authors
report
temperature variations for the Asian subarctic region over the
past 600
years.
What was learned
A graph of the authors' data reveals that temperatures in the
Asian
subarctic exhibited a small positive trend from the start of the
record
until about 1750. Thereafter, a severe cooling trend ensued,
followed by a
130-year warming trend from about 1820 through 1950, after which
temperatures fell once again. In considering the entire record,
the authors
state that the amplitude of 20th Century warming "does not
go beyond the
limits of reconstructed natural temperature fluctuations in the
Holocene
subarctic zone."
In attempting to determine the cause or causes of the temperature
fluctuations, the authors report finding a significant
correlation with
solar radiation and volcanic activity over the entire 600-year
period (R =
0.32 for solar radiation, R = -0.41 for volcanic activity), which
correlation improved over the shorter interval of the industrial
period --
1800 to 1990 -- (R = 0.68 for solar radiation, R = -0.59 for
volcanic
activity).
What it means
It is interesting to note that in this region of the world, where
climate
models predict large increases in temperature as a result of the
historical
rise in the air's CO2 concentration, real-world data show an
actual cooling
trend since around 1940, when the greenhouse effect of CO2 should
have been
most prevalent. And, where warming does exist in the record
(between about
1820 and 1940), much of it correlates with changes in solar
irradiance and
volcanic activity - two factors definitely free of anthropogenic
influence.
Have the climate alarmists try explaining that one to you!
Copyright © 2001. Center for the Study of Carbon Dioxide
and Global Change
===========
(5) URBANIZATION EFFECTS OF TEMPERATURE MESSUREMENTS
From CO2 Science, 14 March 2001
http://www.co2science.org/subject/u/summaries/urbanizationeffects.htm
The putative warming of non-urbanized areas of the planet over
the past
century is believed to be less than 1°C. Urban-induced heating
in large
cities, on the other hand, may be as great as 10°C. Hence,
since nearly all
long-term temperature records have been obtained from sensors
located in
towns and cities that have experienced significant growth over
this time
period, it is extremely important that urbanization-induced
warming - which
can be a full order of magnitude greater then the background
trend being
sought - be removed from the original temperature records when
attempting to
accurately assess the true warming (or cooling!) of the natural
non-urban
environment. In many cases, researchers have attempted to remove
such
effects, but it is clear that this issue is very complex; and it
is likely
that spurious urban warming remains in many of the surface-based
temperature
records.
One prominent method utilized to minimize the effects of
urbanization in
global or regional temperature data sets is to create such data
sets using a
minimum population-based threshold. Records from cities
with populations
above 2000 persons, for example, might be considered to contain
an urban
warming bias and therefore be rejected for inclusion in the data
set. Yet,
even cities with 1000 inhabitants or fewer can possess an urban
heat island
of significant magnitude. Oke (1973), for example, in a
study of urban heat
islands in cities with populations ranging from 1,000 to
2,000,000 people,
presented data indicating that in settlements with as few as
1,000
inhabitants, there was an urban heat island effect on the order
of 2 to
2.5°C - a value over twice as great as the increase in mean
global air
temperature believed to have occurred since the end of the Little
Ice Age.
In another study, Changnon (1999) analyzed soil temperatures
measured at a
totally rural site in Illinois from 1889 to 1952, as well as
contemporary
air temperatures measured at nearby small towns. The results of
his study
revealed the existence of a significant urban-induced warming
bias in the
air temperature records that had not previously been detected, or
even
suspected. Soil temperatures in the totally rural setting
revealed the
existence of a temperature increase that was 0.17°C less than
the 0.57°C
warming determined from three benchmark stations in Illinois with
the
highest quality long-term temperature data, all of which are
located in
communities with populations of less than 2,000 people as of
1990. The
significance of this finding was underscored by Changnon's
statement that
"this could be significant because the IPCC (1995) indicated
that the global
mean temperature increased 0.3°C from 1890 to 1950."
A study of 51 watersheds in the eastern United States also
reveals the
potential for an urban warming bias in climatic records. In this
study, Dow
and DeWalle (2000) report that a complete transformation from
100% rural to
100% urban characteristics results in a 31% decrease in watershed
evaporation and a 13 W/m2 increase in sensible heating of the
atmosphere.
Based upon their results, we calculated that, to a first
approximation, a
transformation from a totally rural regime to a mere 2%
urbanization regime
could increase the near-surface air temperature by as much as a
quarter of a
degree Centigrade (See The Urbanization of America's Watersheds:
Climatic
Implications). This powerful anthropogenic, but non-greenhouse,
effect of
urbanization on the energy balance of the watershed and the
temperature of
the boundary-layer air above it begins to express itself with the
very first
hint of urbanization and, hence, may be most difficult to remove
from
instrumental air temperature records that are used in attempts to
identify
any greenhouse warming that may be present. Indeed, the signal
may already
be present in many temperature records that have been considered
"rural
enough" to be devoid of all human influence, when such is
not really the
case.
Lastly, in this ever-complex issue, we note that urban warming
biases can
develop in a temperature record in cities that have experienced
no change in
population over a given length of time. In a stunning report,
Bohm (1998)
analyzed urban, suburban and rural temperature records in and
around Vienna,
Austria over the 45-year period between 1951 and 1996. During
this time, the
city experienced zero population growth. However, there was a 20%
decrease
in woodland and a 30% decrease in grassland within the city, as
well as a
doubling of the number of buildings, a ten-fold increase in the
number of
cars, a 60% increase in street, pavement and parking area, and a
2.5-fold
increase in energy consumption. Analyses revealed that suburban
stations
exhibited city-induced temperature increases ranging from 0.11 to
0.21°C
over the 45-year period, while the urban stations experienced
city-induced
temperature increases ranging from zero, in the historic center
of the city,
to 0.6°C in the area of most intensive urban development.
Clearly, there is ample opportunity for very large errors to
occur in
attempts to reconstruct true non-urban temperature trends. Given
the
magnitude of these very real errors as illustrated above, it
appears that
more detailed analyses of urban population and development
characteristics
are needed before we can be confident that the global temperature
record of
the past century or so is properly corrected for these phenomena.
And until
this is done, it would be premature to put too much faith in that
record as
it stands today.
References
Bohm, R. 1998. Urban bias in temperature time series - A case
study for the
city of Vienna, Austria. Climatic Change 38: 113-128.
Changnon, S.A. 1999. A rare long record of deep soil temperatures
defines
temporal temperature changes and an urban heat island. Climatic
Change 42:
531-538.
Dow, C.L. and DeWalle, D.R. 2000. Trends in evaporation and
Bowen ratio on
urbanizing watersheds in eastern United States. Water Resources
Research 36:
1835-1843.
Intergovernmental Panel on Climate Change. 1995. Climate Change
1995, The
Science of Climate Change. Cambridge University Press, Cambridge,
U.K.
Oke, T.R. 1973. City size and the urban heat island.
Atmospheric
Environment 7: 769-779.
Copyright © 2001. Center for the Study of Carbon Dioxide and
Global Change
=========
(6) ELEVATED CO2 CONCENTATIONS ON WATER USE EFFICIENCY
From CO2 Science, 1`4 March 2001
http://www.co2science.org/subject/w/summaries/wateruse.htm
As the air's CO2 content rises, most plants exhibit increased
rates of net
photosynthesis and biomass production. Moreover, on a
per-unit-leaf-area
basis, they typically lose less water via transpiration (Saxe et
al., 1998;
Seneweera et al., 1998; Sgherri et al., 1998; Smart et al., 1998;
Tognetti
et al., 1998; Wayne et al., 1998; Centritto et al., 1999a; Serraj
et al.,
1999), as they tend to display lower stomatal conductances at
elevated
atmospheric CO2 concentrations (Egli et al., 1998; Garcia et al.,
1998;
LeCain and Morgan, 1998; Tjoelker et al., 1998; Leymarie et al.,
1999;
Runion et al., 1999; Stanciel et al., 2000). Consequently, plant
water use
efficiency, or the amount of carbon gained per unit of water lost
per unit
leaf area, should increase dramatically as the air's CO2 content
rises. In
this review, we summarize the results of several recent studies
that support
this conclusion.
With respect to C3 agricultural crops, atmospheric CO2 enrichment
nearly
always increases plant water use efficiency. In the study of
Serraj et al.
(1999), soybeans grown at 700 ppm CO2 exhibited dry weight
increases of as
much as 33% over plants grown in ambient air, while using 10 to
25% less
water, thereby boosting their water use efficiencies by 50 to
75%. In
another study, Garcia et al. (1998) found that spring wheat grown
at 550 ppm
CO2 had a water use efficiency that was a third again as great as
that of
ambiently-grown plants; while Hunsaker et al. (2000) reported
that the water
use efficiencies of the same CO2-enriched plants rose by 20 and
10%,
respectively, under high and low soil nitrogen regimes.
Sometimes, atmospheric CO2 enrichment increases the water use
efficiencies
of C3 agricultural crops by even greater amounts. De Luis et al.
(1999), for
example, demonstrated that alfalfa plants subjected to an
atmospheric CO2
concentration of 700 ppm had water use efficiencies that were 2.6
and 4.1
times greater than those displayed by control plants growing at
400 ppm CO2
under water-stressed and well-watered conditions,
respectively. Similarly,
a 2.7-fold CO2-induced increase in water use efficiency was
reported by
Malmstrom and Field (1997) for oats infected with the barley
yellow dwarf
virus, when grown at an atmospheric CO2 concentration of 700 ppm.
Elevated CO2 also enhances the water use efficiencies of crops
possessing
alternate pathways of carbon fixation. Maroco et al. (1999), for
example,
demonstrated that maize - a C4 crop - grown for 30 days at an
atmospheric
CO2 concentration of 1100 ppm had an intrinsic water use
efficiency that was
225% higher than that of similar plants grown at 350 ppm
CO2. And Zhu et
al. (1999) reported that pineapple - a CAM plant - grown at 700
ppm CO2
exhibited water use efficiencies that were always significantly
greater than
those displayed by control plants grown at 350 ppm CO2 over a
wide range of
growth temperatures.
Elevated CO2 concentrations also increase the water use
efficiencies of
various grassland species. In the study of Szente et al. (1998),
for
example, two C3 grasses and two C3 broad-leaved species grown at
twice-ambient levels of atmospheric CO2 exhibited 72 and 366%
increases in
their respective water use efficiencies. Similarly, Clark
et al. (1999)
grew mixed grassland species (C3 and C4) from New Zealand at 700
ppm CO2 and
observed that such plants exhibited significantly greater water
use
efficiencies than their counterparts grown at 350 ppm CO2.
Likewise, LeCain
and Morgan (1998) reported that six different C4 grasses all
exhibited
significant CO2-induced increases in water use efficiency, as did
Seneweera
et al. (1998) for the common C4 grass Panicum coloratum.
Thus, there is
little doubt the vast majority of all agricultural and grassland
plants
respond favorably to elevated concentrations of atmospheric CO2
by
increasing their water use efficiencies.
Most longer-lived perennial plants also have their water use
efficiencies
enhanced by higher concentrations of atmospheric CO2. Arp et al.
(1998), for
example, reported that five of six perennial plants common to The
Netherlands that were subjected to an atmospheric CO2
concentration of 566
ppm exhibited greater water use efficiencies than control plants
fumigated
with air of 354 ppm CO2. Likewise, in a study performed by
Tjoelker et al.
(1998), seedlings of quaking aspen, paper birch, tamarack, black
spruce and
jack pine grown at 580 ppm CO2 for three months all displayed
increases in
water use efficiency, ranging from 40 to 80%. Also, in a
study conducted by
Centritto et al. (1999b), cherry seedlings grown at twice-ambient
levels of
atmospheric CO2 displayed water use efficiencies that were 50%
greater than
those of ambient controls, regardless of soil moisture
status. And in the
study of Wayne et al. (1998), yellow birch seedlings grown at 800
ppm CO2
had water use efficiencies that were 52 and 94% greater than
control plants
subjected to low and high air temperatures regimes,
respectively. Other
trees that have been found to be benefited by extra carbon
dioxide are
longleaf pine (Runion et al., 1999), red oak (Anderson and
Tomlinson, 1998),
silver birch (Rey and Jarvis, 1998), beech (Egli et al., 1998)
and spruce
(Roberntz and Stockfors, 1998).
In some parts of the world, perennial plants have been exposed
for decades
to elevated CO2 concentrations, due to their proximity to
CO2-emitting
springs and vents in the earth's surface. In studying such
plants,
scientists have been able to assess the long-term effects of
elevated CO2
concentrations on water use efficiency. In Venezuela, for
example, the water
use efficiency of a common tree exposed to a lifetime atmospheric
CO2
concentration of approximately 1,000 ppm rose 2-fold and 19-fold
during the
wet and dry seasons, respectively (Fernandez et al., 1998).
Similarly,
Bartak et al. (1999) reported that 30-year old Arbutus unedo
trees growing
in central Italy at a lifetime atmospheric CO2 concentration of
approximately 465 ppm exhibited water use efficiencies that were
100%
greater than those of control trees growing at a lifetime CO2
concentration
of 355 ppm. And two species of mature oak trees growing for
15 to 25 years
at an atmospheric CO2 concentration ranging from 500 to 1000 ppm
in central
Italy displayed "such marked increases in water use
efficiency under
elevated CO2" that the authors concluded it "might be
of great importance in
Mediterranean environments in the perspective of global climate
change"
(Tognetti et al., 1998).
In some cases, scientists have looked to the past and determined
the impact
the historic rise in the air's CO2 content has already had on
plant water
use efficiency. Duquesnay et al. (1998), for example, used
tree-ring carbon
isotope data derived from beech trees to determine that the water
use
efficiency of such trees in northeastern France increased by
approximately
33% over the past century. Similarly, Feng (1999) used
tree-ring carbon
isotope data derived from western North America to infer a 10 to
25%
increase in forest water use efficiency from 1750 to 1970, during
which time
the atmospheric CO2 concentration rose by approximately
16%. In another
interesting study, Beerling et al. (1998) grew Gingko saplings at
350 and
650 ppm CO2 for three years and reported that elevated CO2
reduced leaf
stomatal densities to values comparable to those measured on
fossilized
Gingko leaves dating back to the Triassic and Jurassic periods,
but that it
did not affect photosynthesis, which suggests that at those
earlier times of
greater atmospheric CO2 concentration, these plants were much
more efficient
at utilizing water than they are today. Finally, Nicholson
et al. (1998)
found that rain use efficiency, which is similar to water use
efficiency,
neither increased nor decreased from 1980 to 1995 for the central
and
western Sahel, contrary to the popular view supported by many
international
agencies; while Prince et al. (1998) demonstrated that rain use
efficiency
actually increased, on average, over the whole of the African
Sahel from
1982 to 1990.
So what do these many studies imply? They suggest that as the CO2
content of
the air continues to rise, nearly all of earth's plant life
should exhibit
increases in water use efficiency. It is thus likely that as time
progresses, more and more of the planet's vegetation will expand
into areas
that have been too dry to support much life in the recent past.
Therefore,
one can expect the earth to become ever greener as time marches
on and more
CO2 accumulates in the atmosphere.
References
Anderson, P.D. and Tomlinson, P.T. 1998. Ontogeny affects
response of
northern red oak seedlings to elevated CO2 and water stress. I.
Carbon
assimilation and biomass production. New Phytologist 140:
477-491.
Arp, W.J., Van Mierlo, J.E.M., Berendse, F. and Snijders,
W. 1998.
Interactions between elevated CO2 concentration, nitrogen and
water: effects
on growth and water use of six perennial plant species. Plant,
Cell and
Environment 21: 1-11.
Bartak, M., Raschi, A. and Tognetti, R. 1999.
Photosynthetic
characteristics of sun and shade leaves in the canopy of Arbutus
unedo L.
trees exposed to in situ long-term elevated CO2.
Photosynthetica 37: 1-16.
Beerling, D.J., McElwain, J.C. and Osborne, C.P.
1998. Stomatal responses
of the 'living fossil' Ginkgo biloba L. to changes in atmospheric
CO2
concentrations. Journal of Experimental Botany 49:
1603-1607.
Centritto, M., Magnani, F., Lee, H.S.J. and Jarvis, P.G.
1999a.
Interactive effects of elevated [CO2] and drought on cherry
(Prunus avium)
seedlings. II. Photosynthetic capacity and water relations.
New Phytologist
141: 141-153.
Centritto, M., Lee, H.S.J. and Jarvis, P.G. 1999b.
Interactive effects of
elevated [CO2] and drought on cherry (Prunus avium) seedlings. I.
Growth,
whole-plant water use efficiency and water loss. New
Phytologist 141:
129-140.
Clark, H., Newton, P.C.D. and Barker, D.J. 1999.
Physiological and
morphological responses to elevated CO2 and a soil moisture
deficit of
temperate pasture species growing in an established plant
community.
Journal of Experimental Botany 50: 233-242.
De Luis, J., Irigoyen, J.J. and Sanchez-Diaz, M.
1999. Elevated CO2
enhances plant growth in droughted N2-fixing alfalfa without
improving water
stress. Physiologia Plantarum 107: 84-89.
Duquesnay, A., Breda, N., Stievenard, M. and Dupouey, J.L.
1998. Changes
of tree-ring d13C and water-use efficiency of beech (Fagus
sylvatica L.) in
north-eastern France during the past century. Plant, Cell
and Environment
21: 565-572.
Egli, P., Maurer, S., Gunthardt-Goerg, M.S. and Korner, C.
1998. Effects
of elevated CO2 and soil quality on leaf gas exchange and
aboveground growth
in beech-spruce model ecosystems. New Phytologist 140:
185-196.
Feng, X. 1999. Trends in intrinsic water-use
efficiency of natural trees
for the past 100-200 years: A response to atmospheric CO2
concentration.
Geochimica et Cosmochimica Acta 63: 1891-1903.
Fernandez, M.D., Pieters, A., Donoso, C., Tezara, W., Azuke, M.,
Herrera,
C., Rengifo, E. and Herrera, A. 1998. Effects of a
natural source of very
high CO2 concentration on the leaf gas exchange, xylem water
potential and
stomatal characteristics of plants of Spatiphylum cannifolium and
Bauhinia
multinervia. New Phytologist 138: 689-697.
Garcia, R.L., Long, S.P., Wall, G.W., Osborne, C.P., Kimball,
B.A., Nie,
G.Y., Pinter Jr., P.J., LaMorte, R.L. and Wechsung, F.
1998.
Photosynthesis and conductance of spring-wheat leaves: field
response to
continuous free-air atmospheric CO2 enrichment. Plant, Cell
and Environment
21: 659-669.
Hunsaker, D.J., Kimball. B.A., Pinter, P.J., Jr., Wall, G.W.,
LaMorte, R.L.,
Adamsen, F.J., Leavitt, S.W., Thompson, T.L., Matthias, A.D. and
Brooks,
T.J. 2000. CO2 enrichment and soil nitrogen effects
on wheat
evapotranspiration and water use efficiency. Agricultural
and Forest
Meteorology 104: 85-105.
LeCain, D.R. and Morgan, J.A. 1998. Growth, gas
exchange, leaf nitrogen
and carbohydrate concentrations in NAD-ME and NADP-ME C4 grasses
grown in
elevated CO2. Physiologia Plantarum 102: 297-306.
Leymarie, J., Lasceve, G. and Vavasseur, A. 1999.
Elevated CO2 enhances
stomatal responses to osmotic stress and abscisic acid in
Arabidopsis
thaliana. Plant, Cell and Environment 22: 301-308.
Malmstrom, C.M. and Field, C.B. 1997. Virus-induced
differences in the
response of oat plants to elevated carbon dioxide. Plant,
Cell and
Environment 20: 178-188.
Maroco, J.P., Edwards, G.E. and Ku, M.S.B. 1999.
Photosynthetic
acclimation of maize to growth under elevated levels of carbon
dioxide.
Planta 210: 115-125.
Prince, S.D., Brown De Colstoun, E. and Kravitz, L.L.
1998. Evidence from
rain-use efficiencies does not indicate extensive Sahelian
desertification.
Global Change Biology 4: 359-374.
Nicholson, S.E., Tucker, C.J. and Ba, M.B. 1998.
Desertification, drought,
and surface vegetation: An example from the West African
Sahel. Bulletin of
the American Meteorological Society 79: 815-829.
Rey, A. and Jarvis, P.G. 1998. Long-Term
photosynthetic acclimation to
increased atmospheric CO2 concentration in young birch (Betula
pendula)
trees. Tree Physiology 18: 441-450.
Roberntz, P. and Stockfors, J. 1998. Effects of
elevated CO2 concentration
and nutrition on net photosynthesis, stomatal conductance and
needle
respiration of field-grown Norway spruce trees. Tree
Physiology 18:
233-241.
Runion, G.B., Mitchell, R.J., Green, T.H., Prior, S.A., Rogers,
H.H. and
Gjerstad, D.H. 1999. Longleaf pine photosynthetic
response to soil
resource availability and elevated atmospheric carbon
dioxide. Journal of
Environmental Quality 28: 880-887.
Saxe, H., Ellsworth, D.S. and Heath, J. 1998. Tansley
review no. 98: Tree
and forest functioning in an enriched CO2 atmosphere. New
Phytologist 139:
395-436.
Seneweera, S.P., Ghannoum, O. and Conroy, J. 1998.
High vapor pressure
deficit and low soil water availability enhance shoot growth
responses of a
C4 grass (Panicum coloratum cv. Bambatsi) to CO2
enrichment. Australian
Journal of Plant Physiology 25: 287-292.
Serraj, R., Allen, L.H., Jr., Sinclair, T.R. 1999.
Soybean leaf growth and
gas exchange response to drought under carbon dioxide
enrichment. Global
Change Biology 5: 283-291.
Sgherri, C.L.M., Quartacci, M.F., Menconi, M., Raschi, A. and
Navari-Izzo,
F. 1998. Interactions between drought and elevated
CO2 on alfalfa plants.
Journal of Plant Physiology 152: 118-124.
Smart, D.R., Ritchie, K., Bloom, A.J. and Bugbee, B.B.
1998. Nitrogen
balance for wheat canopies (Triticum aestivum cv. Veery 10) grown
under
elevated and ambient CO2 concentrations. Plant, Cell and
Environment 21:
753-763.
Stanciel, K., Mortley, D.G., Hileman, D.R., Loretan, P.A., Bonsi,
C.K. and
Hill, W.A. 2000. Growth, pod and seed yield, and gas
exchange of
hydroponically grown peanut in response to CO2 enrichment.
HortScience 35:
49-52.
Szente, K., Nagy, Z. and Tuba, Z. 1998. Enhanced
water use efficiency in
dry loess grassland species grown at elevated air CO2
concentration.
Photosynthetica 35: 637-640.
Tjoelker, M.G., Oleksyn, J. and Reich, P.B. 1998.
Seedlings of five boreal
tree species differ in acclimation of net photosynthesis to
elevated CO2 and
temperature. Tree Physiology 18: 715-726.
Tognetti, R., Johnson, J.D., Michelozzi, M. and Raschi, A.
1998. Response
of foliar metabolism in mature trees of Quercus pubescens and
Quercus ilex
to long-term elevated CO2. Environmental and Experimental
Botany 39:
233-245.
Wayne, P.M., Reekie, E.G. and Bazzaz, F.A. 1998.
Elevated CO2 ameliorates
birch response to high temperature and frost stress: implications
for
modeling climate-induced geographic range shifts. Oecologia
114: 335-342.
Zhu, J., Goldstein, G. and Bartholomew, D.P. 1999.
Gas exchange and carbon
isotope composition of Ananas comosus in response to elevated CO2
and
temperature. Plant, Cell and Environment 22: 999-1007.
Copyright © 2001. Center for the Study of Carbon Dioxide
and Global Change
================
(7) MAJOR STUDIES JEOPARDIZE IPCC STORYLINES
From the Environmental News Network, 10 March 2001
http://www.enn.com/direct/display-release.asp?id=3617
From Greening Earth Society
WASHINGTON, DC - In the six short weeks since the
Intergovernmental Panel on
Climate Change released its Third Assessment report on January
20, two major
scientific studies strongly shake its foundation. They may
crumble it
entirely. At risk is the much-publicized conclusion that average
global
temperature will rise between 1.4°C and 5.8°C over the next
hundred years.
The IPCC arrived at that 4.4°C range of potential temperature
increase by
inputting thirty-five different scenarios - each describing an
alternative
IPCC vision of future greenhouse gas and aerosol emissions - into
seven
different climate models. The seven climate models actually were
just one,
tweaked a bit to produce different output.
The major tweaking altered climate sensitivity - how much the
earth warms
for an atmospheric doubling of carbon dioxide from pre-industrial
levels.
The low estimate was 1.7°C; the high, 4.2°C. In order to create
the most
extreme outcome from among the 245 possibilities (35 scenarios x
7 models),
the greatest climate sensitivity was goosed by the most extreme
emissions
scenario, one in which carbon dioxide emissions are high and
aerosol
emissions are low. The result: a 5.8°C temperature rise.
That's the edifice the Third Assessment erects. Let's check the
size of the
termites gnawing away at its foundation.
The first is a study by Stanford scientist Mark Jacobson reported
in the
February 8, 2001, edition of Nature. Jacobson calculates the
warming effect
of atmospheric black carbon (soot) aerosols is more than twice
the value of
that used incorporated in the IPCC calculations. Compounding the
problem,
the IPCC does not anticipate changes in soot concentrations under
any of its
emissions scenarios. The implications are two-fold.
First, the warming effect of the current concentrations of soot
aerosols
goes much further toward balancing out the cooling effect of
sulfate
aerosols than the IPCC admits. Second, the IPCC's anticipated
warming -
predicated on policies that are intended to reduce sulfate
emissions - will
be diminished greatly if soot emissions go down at the same time
sulfate
emissions do.
Power plant technologies that reduce soot (electrostatic
precipitators and
fabric filters) are comparably simpler than those that scrub
sulfate
aerosols (SOx). The fact the IPCC fails to consider soot
reduction is a bit
odd. But, had they, the bounds on the range of future warming
would be much
less.
The second study is more like a seismic shock wave than termite.
In the
March edition of the Bulletin of the American Meteorological
Society, MIT's
Richard Lindzen and two NASA scientists report that they have
identified a
mechanism by which the earth releases extra heat into space.
Lindzen, et al, studied cloud types over the tropical Pacific
Ocean. They
noticed how, when ocean temperature was warm, there were far
fewer
high-level cirrus clouds than when the ocean was cold. Because
cirrus clouds
act like a blanket and keep the earth's warmth from escaping into
space, the
more cirrus clouds there are, the warmer the earth is. It
appears, then,
that the tropical Pacific Ocean is part of "a negative
feedback loop." When
the ocean warms, fewer cirrus clouds result and more heat is lost
to space,
cooling off the ocean.
Lindzen calls this the adaptive infrared iris because it
resembles the way
an eye reacts to changing light. Your eye's iris opens and closes
in order
to maintain a near constant light level. In similar fashion, the
Pacific
Ocean's "iris" apparently opens and closes in order to
maintain a more
constant level of heat.
Having identified this effect through actual observations,
Lindzen and his
colleagues looked to see if several climate models replicated it.
Nope. None
reproduce a now-observed relationship between high-level cloud
coverage and
sea-surface temperatures, among those they examined. They promise
to do
future model testing to learn if others might do so.
The implication of the "adaptive infrared iris" is that
climate's
sensitivity to changes in greenhouse gas levels is much lower
than the IPCC
assumes. Remember that the IPCC fed its climate a model a range
of climate
sensitivities from 1.7°C to 4.2°C. Lindzen finds that if the
same negative
feedback observed in the tropical Pacific is common to all
tropical oceans,
then the range of climate sensitivities should be between 0.64°C
and 1.6°C -
a reduction of about 60 percent in the IPCC numbers.
Take it a step further. If the amount of warming a climate models
predicts
is directly related to the climate sensitivity of the model, the
projected
warming should be reduced by about 60 percent as well. Applying
this
adjustment to the IPCC estimates would revise the range of
potential warming
to something between 0.6°C and 2.3°C. But remember, even that
range would
not reflect proper handling of soot's impact.
The mid-point in the adjusted range, would be about 1.5°C - the
amount of
warming arrived at by fitting climate model output to observed
temperature
changes. That exercise recently was carried out by Patrick
Michaels and Bob
Balling in preparing their book Satanic Gases, and by a research
team led by
Myles Allen who reported in Nature.
For more information, contact:
Chris Paynter
Executive Director
Greening Earth Society
800-529-4503
cpaynter@greeningearthsociety.org
Web site: http://www.greeningearthsociety.org
===========
(8) ARCTIC SEA ICE THICKNESS REMAINED CONSTANT DURING THE 1990s
From John L Daly, 12 March 2001
http://www.microtech.com.au/daly/
This is the self-explanatory title of a recent paper by P. Winsor
of the
Earth Sciences Centre of Göteborg University, Sweden, just
published in
Geophysical Research Letters (GRL v.28, no.6, pp1039-1041, March
15 2001).
The study analysed sea ice thickness data from six submarine
cruises,
concluding - "This extensive data set shows that there was
no trend towards
a thinning ice cover during the 1990s."
The ice area studied was of transects from the Beaufort Sea (just
north of
Canada and Alaska) to the North Pole itself. While the North Pole
has been
the subject of recent scare stories (see special report on the
North Pole
here), this study found that in the Beaufort-North Pole transect,
there was
a slight increase in mean ice thickness at the North Pole and a
slight
decrease in the Beaufort Sea, neither of which was considered
significant in
the study. It was noted however that the Beaufort Sea showed
larger
variability from year to year.
This paper contradicts claims by environmentalists that the polar
sea ice
has been thinning during the 1990s.
=============
(9) GLOBAL WARMING QUESTIONED
From The Observer India, 22 January 2001
http://www.observerindia.com/news/200101/22/commentary05.htm
HYDERABAD
Janardhan Negi, a theoretical geophysicist and emeritus scientist
at the
National Geophysical Research Institute (NGRI) here has made a
controversial
forecast that global warning phase will change to global cooling
and the
temperature anomaly will decline substantially by the year 2030.
According to Negi, his theoretical analysis of existing data
question the
assumption that green house gases like methane and carbon dioxide
generated
by human activity trap the outward radiation from earth leading
to global
warning. Negi has used the temperature anomaly record complied
and updated
up to Septemeber 2000 by the Goddard Institute of the United
States and made
a 'linear auto regressive prediction' beyond year 2030 to show
significant
decline in global temperature from now on.
Negi, who presented his findings at the recent national
conference on ocean
sciences held in Visakhapatnam said that he reached the same
conclusion from
analysis of magnetic susceptibility record of sediments of the
last 3500
years. The sediments act as earth's thermometer and Negi says his
analysis
showed that the earth temperature varied in a cyclic fashion.
According to Negi, the solar activity and not human activity is
contributing
to the observed temperature variations. The sunspots also occur
in a cyclic
fashion with the well-known periodicity of 11 years, 50 years and
180 years.
To highlight the link between global temperature and solar
activity, Negi
says that the number of sunspots fell sharply between 1640 and
1720 around
the time when the earth experienced a cooling of more that 1.2
deg.c.
He says mathematical analysis of global temperature variations
during
1978-1999 as measured by satelites, and for the period 1880-2000
as obtained
from meterological stations showed a 70-80 year periodicity. Negi
argues
that human beings cannot cause or control these cyclic changes
that are
result of 'the complex process of solar system variability and
atmosphere-sea interaction in different space time scales'.
According to the NGRI scientist, there has never been a steady
rise of
global temperature. "The planet is now recovering to the
present levels
after 400 years of cooler climatic phase",he says.
Negi says his conclusion
that the green house gases are not the culprits, is supported by
some of the
observations of the UN intergovernmental panel on climate change
(IPCC)
itself.
For instance Negi notes that most of the observed effective
warming in
twentieth century (about 0.65.c) has come before 1940 while
increase of all
the green house gases occurred after 1940 thus questioning the
role of these
gases in global warning. "Surprisingly the period between
1940 and 1976 -
part of the industrial age - really shows a global cooling
trend," says
Negi. Satellite data and weather balloon measurements during last
two
decades (after 1979) show no warming and in fact show a decline
of 0.24
degrees (c) in 1988-97, says Negi.
The benchmark at the 'Isle of the Dead' (the harbor of Port
Arthur in
southeastern Tasmania) shows no rise of sea level from the year
1841.
"Similarly in recent times the accurate sea level
measurements at
Visakhapatnam (Indian Ocean) also shows no sea level rise during
last 57
years although 100 mm rise was expected during this period",
Negi said. He
also notes that temperature records of Vostok (Antarctica) show
that changes
in values of carbon dioxide follow corresponding temperature
variations
during the last 160,000 years.
If carbon dioxide is indeed causing global warming the reverse
must be the
case, says Negi.
Copyright 2001, The Observer
=============
(10) LITTLE ICE AGE A GLOBAL EVENT
From Greening Earth Society, 6 March 2001
http://www.greeningearthsociety.org/Articles/2001/hockey1.htm
Diane Douglas Dalziel, Ph.D.
Office of Climatology
Arizona State University
During the final decades of the 20th Century, several scientists,
environmentalists, and politicians, and some in the general
public, grew
increasingly concerned over what appeared to be skyrocketing
global
temperatures. The graphic profile of the last 150 years'
temperature even
was dubbed "the hockey stick" because its depiction of
the sharp increase in
annual temperature during the 20th Century steeply ascending out
of the
relatively flat temperature of previous centuries looks like one.
Many
environmental scientists attribute this hockey stick temperature
profile to
increases in anthropogenic greenhouse gases. This is because
using
computer-based General Circulation Models, climatologists have
demonstrated
that a doubling of atmospheric carbon dioxide (CO2) could
theoretically
effect higher global temperatures.
This essay discusses this concern about global warming within the
larger -
in fact, global - context of the Little Ice Age (LIA).
Scientists initially recognized the existence of the LIA in
northern Europe
when they began to study alpine glacial remains and review
historic records
for the 15th to 19th centuries. Colder temperatures, increased
storminess,
and significant advances of alpine glaciers (beginning around
1450 and
ending around 1850), characterized the climatic event. Historic
documents
from Europe, including cod fishery and sea-ice reports for the
17th and 18th
centuries, indicate sea surface temperatures were 3° to 5oC
below the modern
mean. Ice floes penetrated south well beyond their normal extent
and the
European coastline repeatedly was pummeled by torrential
windstorms (Lamb,
1979).
Historic records from northern Switzerland, Germany, the Czech
Republic,
northern Italy, Hungary, Poland, and Spain - records that span
most of the
16th century - indicate that during all seasons, and in all
regions,
temperature dropped markedly during the 1500s (Glaser et al.,
1999). The
onset of warmer and drier conditions during the mid-1800s caused
the retreat
of alpine glaciers. By the early 1900s, climatic conditions were
similar to
those of the present day.
After the LIA was identified in northern Europe, several other
investigations were begun in order to determine the magnitude and
geographic
extent of the LIA phenomenon.
Global Evidence for the Little Ice Age
In addition to investigating glacial geology, scientists study
marine cores,
sea-level curves, tree-ring chronologies, peat bogs, salt
marshes,
stalagmites, historic records, and even human tooth enamel to
determine the
magnitude, timing, and geographic extent of the LIA. The findings
of select
investigations are summarized below. Several others are
summarized in an
attached annotated bibliography.
Glacial Moraines
Glacial geologists who study the timing and magnitude of
late-Holocene
glacial advances use a variety of techniques to date moraines
(the rubble
pushed along by glaciers and left behind when they retreat).
These include
studies of lichens, sediments, tree-ring data from overrun trees,
and carbon
dating of tephras (solid materials ejected from volcanoes and
carried
through the air) and other organic materials.
In Asia, Chen (1987) examined the distribution of Holocene
moraines in the
Tianshan, Qilianshan, and Karakorom Mountains, and the mountains
of
southeastern Tibet. His study identified a widespread synchronous
response
to early Neoglacial events and the LIA. Similarly, Clark and
Gillespie
(1992) identified LIA glacial advances in the Sierra Nevada Range
while
Wiles et al. (1999) identified them in the Prince William Sound
area. In
both instances, they correspond with the LIA in Europe. The LIA
fluctuations
of thirteen glaciers in Prince William Sound largely were
synchronous (on
decadal time scales) and also were synchronous with tree-ring
dated glacial
histories from across the northern Gulf of Alaska.
Several investigations of glacial moraines in alpine areas of
southern New
Zealand similarly show an LIA signature. Moraines of over 130
glaciers have
been analyzed and dated. These chronologies indicate that
glaciers in
Westland National Park experienced three primary glacial maxima
during the
LIA - in 1620, 1780, and 1830 (Wardle, 1973). The Mueller Glacier
on Mt.
Cook achieved its late-Holocene maximum between 1725 and 1730
(Winlker,
2000). Tasman Glacier also achieved its maximum extent during the
LIA
(Purdie and Fitzharris, 1999).
In South America, glacial moraines on the eastern side of
mountains in
southern Chile and below the Arco, Colonia, and Arenales glaciers
have been
examined to identify the effects of late Holocene climate change.
The study
found that all three glaciers reached their maximum extent during
the LIA.
Since that time, they have fluctuated at basically the same rate.
This
implies a common, global climate control (Harrison and
Winchester, 2000).
Similarly, examination of pollen from sediments deposited by
streams flowing
from a glacier in the Venezuelan Andes indicate the Holocene
glacial maximum
took place during the LIA (Valenti, 1998).
In addition to examining glacial tills (the mixture of clay,
sand, gravel
and boulders carried along by the glacier), some researchers have
mapped the
distribution of fresh water ice and frozen sediments in shallow,
saline
lakes in the Andes of southwestern Bolivia in order to understand
the
regional effects of the LIA (Hurlbert and Chang, 1984). The study
mapped
large blocks of fresh water ice (1.5 kilometers long and 7 meters
above the
ice surface) and frozen sediments that extend to an unknown
depth. The ice
blocks evidently formed during the LIA, and now are melting
during summer
months due to undercutting by warm, saline lake water.
In a synthetic analysis of tropical glacier dynamics, Kaser
(1999) found
that tropical glaciers respond differently to climate change than
do mid-
and high-latitude glaciers. As observed on Mount Kenya, tropical
glaciers
can advance in response to lower temperatures even during
relatively dry
periods (Karlen et al. 1999). This study determined that tropical
glaciers
in South America, Africa, and New Guinea reached their maximum
extent at
roughly the same time during the LIA and began to recede in the
mid-1800s.
This further supports the concept of a global LIA signature.
Isotopic Studies
Stalagmites, ice cores, and even teeth provide valuable insight
to global
climate during the LIA when techniques that analyze their
isotopic
composition are applied. Denniston et al. (1999) examined changes
in the
mineral composition of annual layers of stalagmites from a cave
in Pokhara
Valley, Nepal. They noted that there were cooler conditions
between 1550 and
1640, and during two short intervals after 1640. Similarly, Li et
al. (1997)
analyzed changes in the isotopic values of a stalagmite from a
cave near
Beijing. They found that in China the first half of the LIA was
cool and dry
and was followed by cold/wet conditions during the last half.
In New Zealand, oxygen isotope ratios (18O/16O) and carbon ratios
(13C /12C)
from the mineralized layers of a stalagmite were used to
reconstruct a
regional temperature span over the past 5000 years (Wilson et
al., 1979).
The reconstruction clearly depicts a sharp drop in temperature in
the 1400s
and cooler temperatures until the mid-1800s. After that,
temperature began
to increase to pre-LIA levels.
Similarly, in South Africa, the isotopic composition of a
stalagmite from
Cold Air Cave indicates climate was significantly cooler and
drier between
1300 and 1800 than it was before, or has been since. Further, the
researchers determined that the LIA was the dominant climatic
episode
evident from the stalagmite record (Repinski et al., 1999).
In South America, analyses of the isotopic composition of cores
recovered
from the Quelccaya ice cap clearly indicate an LIA signature
(Thompson et
al., 1986). Additionally, the 18O/16O time series from the ice
core exhibits
responses to late-Holocene climate change that are synchronous
with other
regions of both South America (Valero-Garces, 2000) and North
America (Idso,
1988).
Fricke et al. (1995) undertook a unique means of reconstructing
LIA climate.
They analyzed the oxygen isotope content of human tooth enamel.
This
required collecting teeth from the remains of Norsemen and Inuit
that were
excavated from medieval archaeological sites in Greenland. The
18O values
identified in the tooth enamel indicated rapid cooling occurred
in Greenland
between 1400 and 1700. This is concurrent with records of the LIA
in other
regions.
Lacustrine Sediments and Palynology
Studies of sediment composition and pollen assemblages extracted
from lakes,
meadows, and bogs can provide insight as to the timing of climate
change
associated with the LIA. The pollen assemblages of eighteen sites
spread
over eastern North America indicate that changes in floral
communities over
the past 10,000 years generally occurred at different times. This
suggests
local factors dominate change. However, the LIA stands out as a
unique
climatic event with synchronous change in the floral communities
exhibited
in the sites (Grimm and Jacobson, 1992).
Similarly, chemical elements and isotopes from a sediment core
taken from
the bed of Owens Lake in southern California exhibited a clear
LIA signature
(Li et al., 2000). Meanwhile, on the other side of the globe in
southeastern
Ethiopia, the pollen assemblage of a high elevation swamp on Arsi
Mountain
show temperatures dropped roughly 2oC between the 15th and 19th
centuries.
They only returned to pre-LIA temperature in the 1800s.
Examination of the sedimentary history of two high-altitude lakes
on Mount
Kenya and the faunal assemblage (consisting of diatoms and
midges) of a
low-altitude lake near the equator in Kenya provide important
information on
the nature of LIA climate change at different elevations.
Sediments in two
alpine lakes provide insight as to the timing of Holocene glacial
advances.
The faunal assemblage of Lake Naivasha provides insight to the
timing of
droughts and pluvial conditions in the region.
Six Holocene glacial advances were identified in the alpine
lakes. The final
advance occurred during the LIA (Karlen et al., 1999). Lake
Naivasha
revealed drought conditions sometime between 1000 to 1270 that
would
correspond with the Medieval Warm Period (MWP). There were
frequent pluvial
conditions (periods of rainfall) between 1270-1850 that would
correspond
with the LIA (Verschuren et al., 2000). However, three prolonged
droughts
did occur during the LIA between 1390 and 1420, 1560 and 1625,
and between
1760 and 1840. As noted by other investigators, drought in East
Africa does
not negate a LIA signature because glacial advances in that
region primarily
occur in response to colder temperatures (Karlen et al., 1999).
Sediments recovered from saline lakes in northwest Argentina show
a clear
LIA signature (Valero-Garces et al., 2000). Perhaps more
important, the
authors examined their data relative to several other records
including
independent tree-ring reconstructions for central Chile
(precipitation) and
northern Patagonia (temperature), oxygen isotope records from the
Quelccaya
Ice Cap of southern Peru, and historical documents. From this
comparison,
the researchers determined that the onset and termination of the
LIA in
northwest Argentina essentially was synchronous with LIA
signatures from
Chile, Patagonia, and Peru.
Stratigraphic Profiles and Macrofossils
Examination of alluvial deposits in valleys and canyonlands can
help
determine whether LIA climate change occurred at the same time
over broad
regions.
Analyses of relict-river deposits from several valleys of
northeastern Spain
indicate their deposition was synchronous during cool/wet periods
of the LIA
and that the rivers were down-cutting during the warm/dry
conditions of the
MWP. Depositional units were synchronous in nearly all of the
valleys. This
implies a synoptic or global climate signature (Gutierrez-Elorza
and
Pena-Monne, 1998). Similar patterns were evident in LIA riverbed
deposits in
Yellowstone National Park and in the canyonlands of the Colorado
Plateau.
This further suggests a global climatic signature during the LIA
(Wells,
1996).
Examination of macrofossil assemblages from a range of paleosites
also
provides valuable insight into the timing and geographic extent
of the LIA.
Synchronous changes in faunal and floral assemblages at lowland
sites east
of the Andean mountain ranges to cold-adapted species
approximately 440
years ago imply a synoptic or global LIA climate signature (Tonni
et al.,
1999). A review of several previous paleoenvironmental
investigations in
Argentina also reveals synchronous responses to climate change
during the
late Holocene (Iriondo et al., 1993). The review determined that
the MWP in
Argentina was characterized by climatic conditions similar to
those of
today. However, northeastern Argentina was warmer than it is at
present.
Climate deteriorated during LIA. There was increased wind
activity and
shifting of climatic isolines - the lines on a map connecting
similar
climate conditions.
In South Africa, exposure of a paleosol below present mean tide
level of the
Knynsa Lagoon suggests cooler/drier conditions prevailed there
during the
LIA. Preserved, in-situ tree stumps are present. Radiocarbon
dating
indicates that the soil formed during the LIA when lagoon levels
were much
lower than they are at present (Marker, 1997).
Tree-rings as a Climate Signature
Temperature-sensitive trees are common in the world's subalpine
regions.
They have been used to reconstruct warm-season temperature in New
Zealand
and Tasmania, as well as in North America.
In New Zealand, annual ring-widths of five tree-ring chronologies
were
calibrated with observations of historic temperature and used to
reconstruct
temperature from 1400 to the mid-1990s (D'Arrigo et al., 1998).
This study
identified cooler temperatures for the duration of the LIA. There
was a
return to warmer temperatures after 1850.
Although 20th century warming is evident in all of the New
Zealand
chronologies, D'Arrigo notes that recent warming may reflect a
return to
pre-LIA temperatures. According to the researchers, it will be
necessary for
there to be reconstructions extending beyond the LIA in order to
place 20th
century warming in long-term historical context.
In Tasmania, eleven temperature-sensitive chronologies were used
to
reconstruct temperature spanning the late 1700s to the early
1970s (LaMarche
and Pittock, 1982). This 194 year long chronology indicates
cooler
temperatures were present from the mid-1810s to the 1830s, and
from the late
1850s to the late 1870s. Warmer temperatures were present in
between
In North America, fourteen tree-ring chronologies were used to
reconstruct
spring and summer sea surface temperature (SST) for the Pacific
Ocean
between 1750 and 1983. The study found that SST's were coolest
during the
early and middle 1800s, and have warmed since the end of the LIA.
Summary
Each of the studies summarized identify marked cooling of
1.5-2.0oC sometime
between 1400 and 1850. Although there is some regional variation
in the
timing of cooling during the LIA, cold periods typically were
synchronous
over broad regional areas - and often synchronous around the
world. There
was greater variability in the direction of precipitation change.
Some areas
were dry and others wet during different stages of the LIA.
Regional
precipitation variation can be anticipated during any climatic
event due to
atmospheric dynamics, however. Teleconnections associated with
the El Niño
effect result in dry conditions in some regions and wet
conditions in
others.
As a result of numerous investigations identifying cooler
temperatures
between 1400 and 1850, many climate scientists accept as real a
Northern
Hemisphere LIA temperature signature. Fewer are willing to accept
a Southern
Hemisphere LIA temperature signature, however. Nonetheless, it is
clear from
several paleoclimate investigations in Africa, Australia, New
Zealand, and
South America that there is convincing evidence that the LIA
occurred in
those regions as well.
The "hockey stick" curve used to highlight 20th Century
temperature must
therefore be considered within the context of the lower global
temperatures
associated with the LIA
phenomenon. Investigators researching the causes of the LIA have
identified
increased volcanism as a possible contributing force. Most
recognize reduced
solar irradiance as the primary driving mechanism (e.g. Druffel
1982;
Campbell et al., 1998; Free and Robock, 1999; Hong et al., 2000).
As Lean and Rind (1999) point out, solar variability was a
primary forcing
mechanism that triggered the LIA. There should be further
investigation to
ascertain if it is a possible forcing mechanism for 20th Century
warming, as
well.
Selected Bibliography
World Wide Investigations of Climate Change Associated With the
Little Ice
Age
Aa, A.R. 1996. Topographic control of equilibrium-line altitude
depression
on reconstructed "Little Ice Age" glaciers, Grovabreen,
western Norway. The
Holocene, 6 (1)82-89.
Bergeron, Y. and S. Archambault. 1993. Decreasing frequency of
forest fires
in the southern boreal zone of Quebec and its relation to global
warming
since the end of the "Little Ice Age". The Holocene, 3
(3)255-259.
Bickerton, R.W. and J.A. Matthews. 1993. "Little Ice
Age" variations of
outlet glaciers from the Jostedalsbreen icecap, southern Norway;
a regional
lichenometric-dating study of ice-marginal moraine sequences and
their
climatic significance. Journal of Quaternary Science, 8 (1)45-66.
Bjornsson, H. 1996. Scales and rates of glacial sediment removal;
a 20 km
long, 300 m deep trench created beneath Breidamerkurjokull during
the Little
Ice Age. International symposium on Glacial erosion and
sedimentation,
Reykjavik, Iceland. Edited by Holmond, P., N. Humphrey, T.
Johannesson, and
R. Powell.
Proceedings of the International Symposium on Glacial Erosion and
Sedimentation, 22:141-146. Edited by Collins, D. International
Geological
Society.
Bradley, R.S. and P.D. Jones. 1993. Little Ice Age summer
temperature
variations: their nature and relevance to recent global warming
trends. The
Holocene, 3:367-376.
Broecker, W.B. 2000. Was a change in thermohaline circulation
responsible
for the Little Ice Age? Proceedings of the National Academy of
Sciences,
97:1339-1342.
Caseldine, C. and J. Stoetter. 1993. "Little Ice Age"
glaciation of
Troellaskagi Peninsula, northern Iceland; climatic implications
for
reconstructed equilibrium line altitudes (ELAs). The Holocene, 3
(4)357-366.
Curtis, J.H., D.A. Hodell, M. Brenner, and M.W. Binford. 1993.
Little Ice
Age recorded in sediments from Lake Titicaca, Bolivia. American
Geophysical
Union, 1993 fall meeting, San Francisco, CA. EOS Transactions,
American
Geophysical Union, 43:118-119. American Geophysical Union.
Evans, D.J.A. 1997. Reassessment of supposed early-"Little
Ice Age" and
older Neoglacial moraines in the Sandane area of western Norway.
The
Holocene, 7 (1) 121-124.
Grove, J.M. 1988. The Little Ice Age. Methuen: London.
Hass, H.C. 1992. Medieval Warm Period, Little Ice Age and modern
optimum;
the younger depositional history of the Skagerrak (NE North Sea).
American
Geophysical Union 1992 fall meeting, San Francisco, CA. EOS
Transactions,
American Geophysical Union, 73 (43):302. American Geophysical
Union.
Hass, H.C. 1994. The coupling of sediment transport, ocean
currents and
atmsopheric circulation patterns during the Little Ice Age.
American
Geophysical Union 1994 fall meeting, San Francisco, CA. EOS
Transactions,
American Geophysical Union, 75 (44):346-347. American Geophysical
Union.
Jones, V.K. 1974. Little Ice Age and current regimes of an inland
cirque
glacier, and their paleoclimatic implications. Quaternary
Environments
Symposium: Abstracts with Programs, 1974:11-12.
Kipp, N.G. 1973. The Little Ice Age Recorded in Caribbean
Sediment.
International Conference on Mapping the Atmospheric and Oceanic
Circulations
and other Climatic Parameters at the Time of the Last Glacial
Maximum about
17,000 Years Ago, and Comparisons with Today's Conditions and
Those of the
So-called Little Ice Age in Recent Centuries, Abstracts. pp.
94-95.
University of East Anglia: Norwich, England.
Lamb, H.H. 1973. The data available and course established for
the
development of the Little Ice Age in recent centuries in Europe
and other
parts of the world. International Conference on Mapping the
Atmospheric and
Oceanic Circulations and other Climatic Parameters at the Time of
the Last
Glacial Maximum about 17,000 Years Ago, and Comparisons with
Today's
Conditions and Those of the So-called Little Ice Age in Recent
Centuries,
Abstracts, pp. 96-97. Norwich: University of East Anglia.
Landscheidt, T. 1995. Global warming or Little Ice Age? In
Holocene Cycles:
Climate, Sea Levels, and Sedimentation, 17:371-383. Edited by
Finkl, C.W.
Fort Lauderdale, FL: Coastal Education and Research Foundation
(CERF).
Maruszczak, H. 1994. Prices of food products in Polish territory
as index of
climatic oscillations in the Little Ice Age. Geographia Polonica,
63:119-127.
Matthews, J.A., J.L. Innes, and C.J. Caseldine. 1986. C-14 dating
and
paleoenvironment of the historic "Little Ice Age"
glacier advance of
Nigardsbreen, Southwest Norway. In Earth Surface Processes and
Landforms,
11(4):369-375. Wiley & Sons: New York.
Matthews, J.A., A. Nesje, S-O. Dahl. 1996. Reassessment of the
supposed
early "Little Ice Age" and older Neoglacial moraines in
the Sandane area of
western Norway. The Holocene, 6 (1):106-110.
Mikami, T. 1993. Summer temperature variabilities in Japan
reconstructed
from diary weather records during the Little Ice Age. Chigaku
Zasshi
[Journal of Geography], 102 (2):144-151.
Miller, M.M. 1965. Glacier variations in the Little Ice Age and
the problem
of teleconnections. American Geophysical Union 1965 meeting. EOS
Transactions, American Geophysical Union, 46 (1):79. American
Geophysical
Union.
Mizukoshi, M. 1993. Climatic reconstruction in central Japan
during the
Little Ice Age based on documentary sources. Chigaku Zasshi
[Journal of
Geography], 102 (2):152-166.
Molloy, P., and B.D. Marino. 1994. Regional Perspectives on
Icelan's Little
Ice Age; stable isotope ratios 13C and 18O of intertidal marine
bivalve
shells. American Geophysical Union 1994 spring meeting,
Baltimore, MD. EOS
Transactions, American Geophysical Union, 73 (43):302. American
Geophysical
Union.
Perry, C.A. and K.J. Hsu. 2000. Geophysical, archeological, and
historical
evidence support a solar-output model for climate change.
Proceedings of the
National Academy of Sciences, 97 (12):433-438.
Prieto, A. Gioda and M.R. 1999. Histoire des scheresses Andines;
Potosi, El
Nino et le Petit Age glaciaire. La Meteorologie, Vol. 8, No.
27:33-42.
Pfister, C. 1980. The Little Ice Age: Thermal and Wetness Indices
for
Central Europe. Journal of Interdisciplinary History, 10:665-696.
Ramesh, R. 1993. First evidence for Little Ice Age and Medieval
Warming in
India. American Geophysical Union 1993 fall meeting, San
Francisco, CA. EOS
Transactions, American Geophysical Union, 74 (43):118. American
Geophysical
Union.
Selsing, L., O. Foldoy, T. Loken, S.E. Pedersen, E. Wishman.
1991. A
preliminary history of the Little Ice Age in a mountain area in
SW Norway.
International conference on Climate of the northern latitudes:
past, present
and future, Tromso, Norway. Edited by Larsen, E., K. Henriksen,
K-D.,
Vorren. Climate of the Northern Latitudes: Past, Present and
Future, 71 (3):
223-228. Edited by Morten, H. Universitetsforlaget.
==========
(11) MORE EVIDENCE FOR THE GLOBAL EXTENT OF THE LITTLE ICE AGE
From CO2 Science, 7 March 2001
http://www.co2science.org/journal/2001/v4n10c1.htm
Reference
Johnson, T.C., Barry, S., Chan, Y. and Wilkinson, P. 2001.
Decadal record of
climate variability spanning the past 700 yr in the Southern
Tropics of East
Africa. Geology 29: 83-86.
What was done
The authors present a high-resolution 700-year record of climate
variability
in tropical Africa derived from profiles of biogenic silica
abundance in
varved sediment cores retrieved from northern Lake Malawi, Africa
(near
10°S, 34°E).
What was learned
Century-scale changes in biogenic silica were noted throughout
the record.
Low concentrations (warmer conditions) prevailed throughout most
of the
period between 1300 and 1520 A.D. and between the late 1800s and
the
present. High concentrations (colder conditions) were
sustained between
1570 and 1820. This biogenic silica record correlates well
with oxygen
isotope records from Quelccaya, Peru and the South Pole, which
also indicate
the presence of the Little Ice Age.
What it means
The results of this study clearly indicate that the
well-developed Little
Ice Age of the Northern Hemisphere was strong enough to influence
even the
normally-warm Southern Hemispheric tropics. In
contradiction of the claim
of the climate alarmists that the Little Ice Age was purely a
localized
Northern Hemispheric phenomenon, the authors thus conclude that
the Lake
Malawi records "further support, and extend, the global
expanse of the
Little Ice Age."
Copyright © 2001. Center for the Study of Carbon Dioxide
and Global Change
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