"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

    CO2 Science, 14 March 2001

    CO2 Science, 14 March 2001

    Chicago Tribune, 12 March 2001

    CO2 Science, 14 March 2001

    CO2 Science, 14 March 2001

    CO2 Science, 1`4 March 2001

    Environmental News Network, 10 March 2001

    John L Daly, 12 March 2001

    The Observer India, 22 January 2001

     Greening Earth Society, 6 March 2001

     CO2 Science, 7 March 2001


From CO2 Science, 14 March 2001

Cerveny, R.S. and Shaffer, J.A.  2001.  The moon and El Nio.  Geophysical
Research Letters 28: 25-28.

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 Nia conditions,
while low MLDs were associated with El Nio 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
Nia 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 Nio 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 Nio (either La Nia or neutral) conditions."
Copyright 2001. Center for the Study of Carbon Dioxide and Global Change 


From CO2 Science, 14 March 2001

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 (35.2N, 81.5E, 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

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 3C
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 7C decrease between 250 and 280 AD and a
7C increase between 550 and 580 AD. Another 7C 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


From Chicago Tribune, 12 March 2001,2669,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

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


From CO2 Science, 14 March 2001

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

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

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


From CO2 Science, 14 March 2001

The putative warming of non-urbanized areas of the planet over the past
century is believed to be less than 1C. Urban-induced heating in large
cities, on the other hand, may be as great as 10C.  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

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
2.5C - 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 0.17C less than the 0.57C
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 0.3C 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

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 0.21C
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 0.6C 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.


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:

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:

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 


From CO2 Science, 1`4 March 2001

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.


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:

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
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Runion, G.B., Mitchell, R.J., Green, T.H., Prior, S.A., Rogers, H.H. and
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Saxe, H., Ellsworth, D.S. and Heath, J.  1998.  Tansley review no. 98: Tree
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Journal of Plant Physiology 25: 287-292.

Serraj, R., Allen, L.H., Jr., Sinclair, T.R.  1999.  Soybean leaf growth and
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Sgherri, C.L.M., Quartacci, M.F., Menconi, M., Raschi, A. and Navari-Izzo,
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Copyright 2001.  Center for the Study of Carbon Dioxide and Global Change


From the Environmental News Network, 10 March 2001

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 1.4C and 5.8C over the next hundred years.
The IPCC arrived at that 4.4C 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 1.7C; the high, 4.2C. 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 5.8C 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

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 1.7C to 4.2C. 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 0.64C and 1.6C -
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 0.6C and 2.3C. But remember, even that range would
not reflect proper handling of soot's impact.

The mid-point in the adjusted range, would be about 1.5C - 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
Web site:


From John L Daly, 12 March 2001

This is the self-explanatory title of a recent paper by P. Winsor of the
Earth Sciences Centre of Gteborg 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.


From The Observer India, 22 January 2001


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)

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


From Greening Earth Society, 6 March 2001

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,

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,

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

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

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,

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.


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 Nio
effect result in dry conditions in some regions and wet conditions in

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

Selected Bibliography
World Wide Investigations of Climate Change Associated With the Little Ice
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

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,

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
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From CO2 Science, 7 March 2001

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
10S, 34E).

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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