Transcript Folie 1 - hvonstorch.de

Historical dimensions of
climate and climate change
Hans von Storch
Institute for Coastal Research
GKSS Research Center
Geesthacht, Germany
and CliSAP
(Integrated Climate System Analysis and Prediction),
Hamburg, Germany
5 December 2008, Stockholm
Historical dimensions
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Climate in historical times
- intellectually appealing
- relevant for assessing ongoing climate
change - whether it is anthropogenic or entirely
caused by natural processes
Thinking about climate, climate change and
society
(1) ideas about anthropogenic influence on
climate
(2) ideas about the influence of climate and
climate change on humans and societies
Thinking about climate, climate change and society
(1) ideas about anthropogenic
influence on climate
A history of
human
perceptions of
anthropogenic
climate change
in the past
1000 years
Hans von Storch
and
Nico Stehr
List of historical cases of
perceived anthropogenic cimate
changes
Our list should not be mistaken
as an attempt to belittle the
presently voiced concerns about
anthropogenic climate change.
Religious Interpretations
• Religious interpretations of climate anomalies, such as
the prolonged wet period in England in the early 14th
century, explained the adverse climatic conditions as the
divine response to people’s life-style.
• In medieval times, for instance, it was proposed that
climatic anomalies, or extreme events, were a
punishment for parishes which were too tolerant of
witches. Of course, witches were believed to be able to
directly cause adverse weather.
• This practice is also used nowadays. A recent example
has been reported by Berlingske Tidende, 11 April 1998
about the religious interpretations of violent tornadoes in
Alabama during Eastern 1998.
1
Improving climate by human
stewardship
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Our oldest case documented by contemporary
scientific writing refers to the climate of the North
American colonies (Williamson, 1771). The physician
Williamson analyzed the changes of climate, and
related them to the clearing of the landscape by the
settlers.
This is a case in which human action was perceived as
having a beneficial impact on climate.
More cases during the medieval times, related to
colonization by monks, are described by Glacken
(1967).
2-4
Tambora 1816 and lightning rods
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In many parts of Europe, the summer of 1816 was
unusually wet, presumably because of the eruption of
the volcano Tambora.
However, people attributed the adverse conditions to
the new practice of using lightning conductors. The
case is documented in two articles published in the
newspaper Neue Züricher Zeitung (21 June and 9 July
1816). The authorities called the concerns
unsubstantiated and issued grave warnings
concerning violent and illegal acts against the
conductors.
Interestingly, it is mentioned that some years earlier in
Germany, people blamed the conductors for being
responsible for a drought.
6
Debate about climate change – in
the late 19th century
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In the 19th century scientists in Europe and in North America
were confronted with the concept that the climate would be
constant on historical time scales; however, scientists found
significant differences between mean precipitation and
temperature when averaged over different multi-year periods
(e.g. Brückner, 1890).
Also, scientists claimed that the water levels of rivers would fall
continuously. This led to the detection of non-constant climatic
conditions — in modern terms: interdecadal natural variability —
and to the hypothesis that the observed changes are caused by
human activities, mainly deforestation or reforestation.
A debate was hold about two alternative explanations, namely a
systematic climate change mainly related to deforestation or
unknown cosmic drivers, or natural fluctuations on time scales of
decades of years. It seems that the majority adopted the concept
of man-made causes over the natural variability hypothesis.
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Very old and wide-spread is the opinion that forests have an important impact
on rainfall. And indeed, a priori, this seems quite likely.
First of all forests are natural barriers to wind-driven air masses, which are
then, as when encountering hills and mountains, forced to rise. No matter how
light this upward drift may be, in theory it will have to lead to more
condensation at its windward side. But the forest’s influence is also felt in the
fact that the air above stays relatively humid. Forests slow down the swift
runoff of the rainwater and store the water in the ground which is then
evaporated back into the air through the tree tops. This process again must
bring about an increase in precipitation above the forest, the more so as
because of the strong friction between wind and forest surface and the
resulting delay in air flow the moist air tends to stagnate above the forest. If
forests enhance the amount and frequency of precipitation simply by being
there, deforestation as part of agricultural expansion everywhere, must
necessarily result in less rainfall and more frequent droughts. This view is most
poignantly expressed by the saying: Man walks the earth and desert follows his
steps!
Klimaschankungen seit 1700.
E.D. Hölzel,Wien, 1890
In 1836 Rivière advocated the theory of deforestation for parts of southern
France at the Academy in Paris; frost damage followed by the clearing of olive tree
plantations has presumably caused a considerable reduction in rainfall and dried-up
springs in the years from 1821 to 22. The question of climate change due to
destruction of forests has been raised in France many times, e.g. it was pointed out
before the French Chamber of Deputies that the climate of the Départements
Pyrénées Orientales and the Hérault had turned dryer and warmer after the
destruction of forests. Because of these reports the French legislature took a serious
look at the subject of reforestation.
In the Unites States deforestation plays an important role as well and is
seen as the cause for a reduction in rainfall, which is believed to have been observed in
the New England States and also in the Pacific States; F. B. Hough in his capacity as
committee chairman of the American Association for Advancement of Science
demands decisive steps to extend woodland in order to counteract the increasing
drought.
In 1873, in Vienna, the Congress for Agriculture and Forestry discussed the
problem in detail; and when the Prussian House of Representatives ordered a special
commission to examine a proposed law pertaining to the preservation and
implementation of forests for safeguarding, it pointed out that the steady decrease in
the water levels of Prussian rivers was one of the most serious consequences of
deforestation only to be rectified by reforestation programs. It is worth mentioning
that at the same time or only a few years earlier the same concerns were raised in
Russia as well and governmental circles reconsidered the issue of deforestation.”
Klimaschankungen seit 1700.
E.D. Hölzel,Wien, 1890
Influence of battles, radio, nukes
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There are reports that the extensive gun-fire during the
first World War caused excessive rainfall. (hear-say)
Claims have been made that already in classical times
battles had caused rainfall.
The initiation of short wave trans-Atlantic radio
communication were blamed for wet summers in the
1910s and 20s. (hear-say)
After World War II, the new practice of exploding
nuclear devices in the atmosphere caused widespread
concern about the climatic implications of these
experiments. According to Kempton’s analysis, even
nowadays many lay-people are concerned about this
link.
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CO2 – first round of attention
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In the first part of the 20th century a remarkable warming took
place in large parts of the world.
In 1933, this warming was documented, and the uneasy question
„Is the climate changing?“ was put forward in Monthly Weather
Review (Kincer, 1933).
Some years later, Callendar (1938) related the warming to human
emissions of carbon dioxide into the atmosphere, a mechanism
described some 40 years earlier by Arrhenius (1898). Flohn
(1941) also brought this line of reasoning into the scientific
debate.
Interestingly, Arrhenius himself stated that anthropogenic
emissions of CO2 would cause an significant climate change only
after several hundred years (Arrhenius, 1903).
In the 1940s global mean temperatures began to fall – which
eventually led to claims that Earth was heading towards a new Ice
Age.
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The cooling
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After World War II scientists noticed a cooling
and some speculated about whether this
cooling was the first indication of a new Ice
Age, possibly brought on by human actions,
mostly emissions of dust and industrial
pollution.
It was speculated that human pollution would
increase by a factor of as much as 8 which
could increase the opacity of the atmosphere
within hundred years by 400%. This would
reduce incoming sun light causing the global
mean temperature to sink by 3.5 C. Such a
cooling would almost certainly be enough to
force Earth into a new Ice Age (Rasool and
Schneider, 1971).
The prospect was illustrated with the words:
„Between 1880 and 1950, Earth’s climate was
the warmest it has been in five thousand years.
... It was a time of optimism. ... The optimism
has shriveled in the first chill of the cooling.
Since the 1940s winters have become subtly
longer, rains less dependable, storms more
frequent throughout the world.“ (Ponte, 1974).
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Siberian rivers and
other Sovjet ideas
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In Russia, plans for re-routing Siberian rivers southward have been
discussed since the beginning of this century. The plans visualize
benefits in supplying semi-arid regions with water, and an improved
regional climate.
A byproduct was thought to be an ice-free Arctic ocean because of the
reduced fresh water input from the rivers. This would shorten the
winters and extend the growing season; the increase of evaporation
from the open water would transform the Arctic climate into a maritime
climate with moderate temperatures and busy harbors along the
Soviet Union’s North coast.
Such plans were formally adopted in 1976 at the 25th Assembly of the
Soviet Communist Party.
Scientists from the West as well as from the Soviet Union opposed
these plans and warned that the formation of an ice-free Arctic could
significantly affect the global ocean circulation and thus global climate.
Eventually, the plans were abandoned although a more careful
analyses indicated that the probability of melting the Arctic sea ice
associated with a rerouting of the rivers was overestimated.
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Rerouting ocean currents,
artificial lakes
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The New York engineer Riker suggested in 1912
changing the Gulf Stream with the purpose of improving
the climate not only in North America but also the Arctic
and Europe. Riker’s idea was: „A simple jetty 200 miles
long from Cape Race on Newfoundland to a point just
beyond the underwater Grand Banks would keep the
Labrador Current and the Gulf Stream apart ... Half of
the Gulf Stream would throw increased warmth against
Northern Europe, and half would thrust into the Arctic...
The benefits of this would be enormous .... Fog would
disappear, ... all ice in the Arctic would melt. The melting
of the Arctic would improve the world climate in two
ways. ... Europe and North America would be freed of
chilling storms and icy ocean currents... And without the
North Polar ice, the surviving ice pack at the South Pole
would become the heaviest part of our planet. Centrifugal
force would then tip the Earth ... With the Northern
hemisphere tipped more towards the sun, Europe and
North America could expect warmer climate.“.
The idea of modifying ocean currents was later pursued
by scientists from the USA, USSR and other nations. In
most cases, these schemes revolved around the building
of dams, which would for instance block the flow through
the Bering Strait.
12
Damming the Congo
River at Stanley Hill
to irrigate the Sahara
with a “Second Nile”
Note also dams
throughout the
Mediterranean
From Jim Fleming
Ring of dust particles in orbit to
increase solar energy absorption,
melt the ice caps and illuminate
the arctic circle — proposed
separately by Gorodsky and
Cherenkov in 1958 and 1960.
From Jim Fleming
Utopian Geoengineering?
From Jim Fleming
Military use
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Close to the idea of climate engineering is the military use of climate
modifications. The idea to change the course of the Gulf Stream had
been put forward already in the 18th century by Benjamin Franklin, who
envisaged a northward diversion of the Gulf Stream as a powerful
weapon against the British Empire.
A perceived attack using climate as a weapon is a purported Soviet plan
in the 1950s to build a „jetty 50 miles or more long out from near the
eastern tip of Siberia. The jetty would contain several atomic powered
pumping stations that would push cold Arctic waters down through the
Bering Strait. This would ... inject increasing amounts of icy waters into
the ocean current that flows down the west coast of Canada and the
United States. The result would be colder, more stormy weather
throughout North America and enormous losses to the American
economy in agriculture, work days and storm damage.“.
Concern about the development of climate weapons lead to a series of
diplomatic discussions. During a summit meeting 1974 the United States
and the Soviet Union issued a Joint Draft Treaty: „Each State Party to this
Convention undertakes not to engage in military or other hostile use of
environmental modification techniques having widespread, long-lasting or
severe effects as the means of destruction, damage or injury ... the term
‘environmental modification techniques’ refers to any technique for
changing – through the deliberate manipulation of natural processes –
the dynamics, composition of the Earth, including its biota, lithosphere,
hydrosphere and atmosphere ... so as to cause such effects as ...
changes in weather pattern, ...in climate patterns, or in ocean currents.“
13
1954
From Jim Fleming
From Jim Fleming
From Jim Fleming
Supersonic transport
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In the 1960s and 70s aircraft industries in the USA, Europe and Soviet
Union designed supersonic civil air planes.
These plans provoked substantial criticism. Scientist argued that the
exhaust from such planes would damage the ozone layer in the
stratosphere and the climate in general. In the USA the plans were
stopped, but in Europe the Concorde was built and in the Soviet Union
the TU 144.
Of course, numerous military supersonic aircraft are nowadays cruising
the lower stratosphere.
For many years, the discussion about the impact of air traffic on the
climate ceased. But in the early 1990s the topic re-entered the public
debate, this time regarding high-flying conventional jet liners. The focus
of concern is the effect of contrails and exhaust gases on the radiative
balance of Earth. Scientists regard present effects from these sources as
minor compared to other effects. However, some argue that with present
projections of future passenger numbers and technology the effect may
or will be significant.
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Space traffic
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A popular, but for natural scientists somewhat
surprising mechanism links space traffic to a
deteriorating global climate. In Kempton et al.’s (1995)
interviews with lay people, this mechanism is
mentioned several times. 43% of the respondents in
Kempton’s survey considered the statement „there
may be a link between the changes in the weather and
all the rockets they have fired into outer space“
plausible.
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deforestation, part II
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The ongoing deforestation of tropical forests is of great
concern to many people, who are afraid not only of
reduction in the variety of species but also of changes
in global climate (Kempton et al., 1995; Dunlap et al.,
1993).
Model calculations indicate that these land use
modifications cause significant local and regional
changes whereas in most model calculations global
effects are marginal.
Interestingly, similar results were obtained for the
climatic implications of the transformation of the North
American wilderness into agricultural land (Copeland
et al., 1996).
16
Aerosols, nuclear winter
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Anthropogenic aerosols are considered powerful agents for
changing the global climate.
One scenario deals with the emission of aerosols mainly
from burning forests and fossil fuels. A dramatic version is
that of „nuclear winter“ – in which it was assumed that the
explosion of a multitude of nuclear bombs in a future war
would create a high flying veil of soot particles which would
effectively shut off solar radiation and cause a collapse of
the biosphere.
Support came from a number of computer simulation. The
ignition of the Kuwait oil wells in the aftermath of the 1991
Gulf War led some scientists to expect a minor nuclear
winter, particularly with respect to the Indian Monsoon. It
turned out that the effect was severe locally but insignificant
on the larger scales.
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Break down of Gulf Stream
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A recent line of concern, especially in Europe, refers to the stability of the
Gulf Stream.
Ocean models exhibit a markedly nonlinear behavior of the Atlantic
circulation with two stable states, one with an active Gulf stream and another
with a weakened northward transport moderating the European climate.
Both states are stable within a certain range of conditions, but when the
system is brought to the margins of these ranges, it can switch abruptly to
the other state.
Paleoclimatic reconstructions using evidence from ice cores and other
indirect sources support the existence of such stable states and frequent
rapid changes from one state to another. During the present interglacial
period from about 10,000 years go to the present, such rapid climate
changes have not been detected.
In the global warming debate the risk of a „collapse“ of the Gulf Stream is put
forward. While the globe is becoming warmer, Europe and Northeast
America would experience colder conditions with the possibility of a new ice
age.
Not only global warming is presented as a human lever for terminating the
Gulf Stream. Another hypothesis was published by the Transactions of the
American Geophysical Union. The human culprit was the Assuan Dam in
Egypt which would reduce the flow of fresh water into the Mediterranean
Sea. This reduction along with enhanced evaporation caused by global
warming would result in a saltier outflow from the Mediterranean Sea into
the Atlantic eventually causing the Gulf Stream to flip over.
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Thinking about climate, climate change and society
(2) ideas about the influence
of climate and climate change
on humans and societies
Map of „mental energy“ conditioned by climatic
conditions
E. Huntington
Distribution of civilizations in 1916, according to
expert opinion.
Davies‘ (1923, 1929
and 1932) „nose
index“ derived
from observations
and estimated
from temperature
and humidity data.
The case of
Eduard Brückner
– solid climate
research but
unexpected
social and
technological
developments.
Hans von Storch
& Nico Stehr
Practical importance of climate fluctuations.
“Are climate variations so significant that they
are of practical impact? Indeed they are.”
In dry areas in particular where water is notoriously scarce the hydrographic
conditions change dramatically during periods of climatic variations. Lakes disappear
during dry periods and reappear during wet ones, as for instance Lake George in New
South Whales which in 1820 and again in 1876, and to a lesser extent in 1850, used to be a
large lake of 12 to 18 kilometres in length, 10 kilometres in width, and 5 to 8 meters in
depth, yet disappeared completely in the dry periods in between; or some central African
lakes such as the Tshad, Tanganyika and Nyassa, which at times rise so high that their
overflowing waters create an outlet lasting for some years and which then lose this outlet
again when the dry period begins. Rivers and creeks dry out for a full decade; swamps dry
up and reappear in the next wet period.
Consequently climatic variations deeply affect human life. River navigation to a
great extent depends on the amount of water in the river bed which determines its depth.
In those dry years around 1830 and 1860 shipping problems increased and soon a lot of
speculation began about the possible cause of the lower river-water levels. In most cases
the increasing practice of deforestation was found to be the source. Now we know better:
it is because of climatic changes.
Another way in which temperature variations are affecting traffic is through
the length of time of the rivers’ freeze-up. For example, during the cold spill from 1806—
1820 the Newa and the harbor of St. Petersburg remained blocked by ice for more than
three weeks longer than they did during the warm period from 1821—1835. This means
that during cold years harbors in a more westerly location and with shorter closure times
handle part of St. Petersburg’s shipping traffic which they lose again during warm
periods. Thus certain changes in shipping traffic go hand in hand with climate changes.
Klimaschankungen seit 1700.
E.D. Hölzel,Wien, 1890
The case of
typhoid
Klimaschwankungen und Völkerwanderungen
Climate variability and mass migration
Vortrag Kaiserliche Akademie der Wissenschaftern,
Wien 1912
Precip crop prod.
Variability of Rainfall and Wheat
Prices in England
Rainfall (R) is indicated in deviations
from mean (percentages) (1 = 2.5%),
the annual average wheat price (W) in
Shillings per Imp. Quarter (1 = 2 sh.).
Variability of Rainfall in
Relation to the Grain Crop in
Prussia
The Grain Crop (WZ = Wheat
Crop, RO = Rye Crop) is in
percentages of an average
crop, i.e. in deviation from a
multi-year mean ( 1 indicator =
5% deviation); rainfall (R) is
also in deviations (%) from the
mean (1 indicator = 4%).
Variability of Rainfall and Emigration
from the German Empire to the
United States
The curves are based on five-year
totals. Rainfall is in deviations
(percentages) from the multi-year
mean. Emigration to the United States
is in 10,000.
Variability of Rainfall in the United States and
Western Europe and the Total Number of
Immigrants to the U.S. and from Britain.
The curves are based on five year totals. The
number of immigrants is given in 10,000, rainfall in
deviation (percentages) from the multi-year mean..
30 years later …
• Freezing of rivers became insignificant for
transportation because of rail systems.
• Typhoid problem was solved by progress in
pharmaceutical measures
• Power of nations depends no longer on
agricultural production but on industrial strength.
• Emigration is no longer driven by success of
agriculture.
• SOCIAL CHANGE WAS MORE IMPORTANT
THAN CLIMATE CHANGE
… and today?
• Certain culturally constructed views of
climate change
- drastic signs (palms)
- disaster
• How is the relationship of climate and
society?
Hasselmann, 1990
Perceived Environment and Society (PES) model
Stehr and von Storch, 1993