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Climate Change: Present, Past, and Future

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Climate Change: Present, Past, and Future Based on an article and graphics by David S. Chapman and Michael G. Davis, Department of Geology and Geophysics, – PowerPoint PPT presentation

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Title: Climate Change: Present, Past, and Future


1
Climate Change Present, Past, and Future
  • Based on an article and graphics by David S.
    Chapman and Michael G. Davis, Department of
    Geology and Geophysics, University of Utah, Salt
    Lake City, Utah
  • featuring datasets considered by
    the Intergovernmental Panel on Climate Change
  • and the National Research Council

Slide set produced by LuAnn Dahlman NOAA climate
office
2
Introduction
This presentation shows scientific estimates of
global average temperature from 1000 to 2100.
Each dataset, calculated from instrumental
records, proxy records, or projections, has been
published in peer-reviewed literature.
Additional information explaining how those
temperatures were derived is on the slides that
follow the graphs of the datasets. Full citations
for each dataset are included on the explanation
slides. Notes about each slide are available
in the downloadable PowerPoint, in Normal view.
3
  • Paleoclimatology The study of past climate, from
    times prior to instrumental weather measurements.
  • Proxy Data Information from natural recorders
    of climate variability.
  • Widely used proxy climate data include
  • Corals
  • Tree Rings
  • Ice Core records
  • Fossilized Tree Pollen
  • Boreholes
  • Glacier Lengths

4
  • Paleoclimatology - The study of past climate,
    from times prior to instrumental weather
    measurements.

Corals
Corals build their hard skeletons from calcium
carbonate, a mineral extracted from sea water.
The carbonate contains isotopes of oxygen, as
well as trace metals, that can be used to
determine the temperature of the water in which
the coral grew. These temperature recordings can
then be used to reconstruct climate when the
coral lived.
Shown above are two sections of a coral core from
the Galapagos. The cores are x-rayed so
scientists can see the growth bands. Next,
segments are marked for sampling black lines
represent annual bands, blue and red lines
subdivide the year into quarters. The core is
then cut along the lines and the individual
segments analyzed in a laboratory .
5
Paleoclimatology - The study of past climate,
from times prior to instrumental weather
measurements.
Tree Rings
Since tree growth is influenced by climatic
conditions, patterns in tree-ring widths,
density, etc, reflect variations in climate. In
temperate regions where there is a distinct
growing season, trees generally produce one ring
a year, and thus record the climatic conditions
of each year. Trees can grow to be hundreds to
thousands of years old and can contain
annually-resolved records of climate for
centuries to millennia. Shown at right is a
cross section of a young conifer
6
Paleoclimatology - The study of past climate,
from times prior to instrumental weather
measurements.
Ice Cores
Located high in mountains and the polar ice caps,
ice accumulates from snowfall compressed over
many thousands of years. Scientists drill
through the deep ice to collect ice cores that
contain dust, air bubbles, or isotopes of oxygen,
that can be used to interpret the past climate of
that area.
Shown above is a section of an ice core taken on
the Clark Glacier in the McMurdo Dry Valleys. A
160-meter core was extracted to study the climate
in the area over the past 2,000 years.
7
Paleoclimatology - The study of past climate,
from times prior to instrumental weather
measurements.
Fossilized Pollen
All flowering plants produce pollen grains. Their
distinctive shapes can be used to identify the
type of plant from which they came. Pollen grains
are well preserved in the sediment layers of
ponds, lakes or the ocean. An analysis pollen
grains in each layer tell us what kinds of plants
were growing at the time the sediment was
deposited. Inferences can then be made about the
climate based on the types of plants found in
each layer. The image right, shows features of
pollen spores from the Florida Everglades (USGS)
8
Paleoclimatology - The study of past climate,
from times prior to instrumental weather
measurements.
Glacier Lengths
A study of glacier length over time indicates the
change in temperature. Scientists have recorded
the activity of 169 glaciers from around the
world. A glacier that is becoming longer is
growing due to accumulation of snow. A glacier
that is receding is loosing mass. Most glaciers
world wide are showing similar loss of mass.
The image, above, is an aerial view of glaciers.
9
Paleoclimatology - The study of past climate,
from times prior to instrumental weather
measurements.
Borehole data
Borehole data are direct measurements of
temperature from boreholes drilled into the Earth
crust. Departures from the expected increase in
temperature with depth (the geothermal gradient)
can be interpreted in terms of changes in
temperature at the surface in the past. These
changes in temperature have slowly diffused
downward, warming or cooling layers meters below
the surface.
The image to the right is a borehole drill.
10
From 1850 through the present, systematic
instrumental measurements of temperature can be
compiled to estimate annual values for average
global temperature. This record is shown in
black, below.
11
All proxy records, shown by the green line, are
smoothed to reflect variation on the scale of
decades or longer. Note the similarities of the
proxy and instrumental records from the year 1800
to present.
12
Additional sets of proxy records, drawn in the
next few slides, show similar patterns.
13
Additional sets of proxy records, show a similar
patterns.
14
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17
This line represents the change in temperature of
1.1 C since the 1700s.
18
The next few slides show projections of future
temperature based on the IPCC scenarios C3, B1,
A1B, A2. Each scenario is slightly different,
and less optimistic. In the C3 storyline, CO2
concentrations are held at the same level as they
were in 2000. The projection indicates that the
world will continue to warm through 2100 due to
the lengthy response time of the climate system.
B1 population peaks at about 8.7 billion at
mid-century, then declines to around 7 billion at
the end of the century. In this scenario,
countries come together to use both technology
and general environmental controls to decrease
emissions, leading to a temperature increase of
less than 2C above the year 2000 level. The A1B
story line has population peak around 8.7 billion
at midcentury, then decrease toward 7 billion at
the end of the century. This scenario entertains
efficient technologies with a balance between
fossil fuel and non fossil fuel energy sources.
Global temperature increase in scenario A1B is
2.5C. In scenario A2, population increases at
current growth rates to 15 billion in 2100,
accompanied by a heterogeneous economic theme of
self- reliance and preservation of local
identities. Global temperature increase with
scenario A2 approaches 4C by 2100.
19
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23
Note The next few slides provide more
information and credits for the datasets
presented in this PowerPoint. They are optional
information.
24
Instrumental Record Surface temperatures for
Earth are most reliably known for the period 1850
to present. This is the time for which there has
been reasonable global coverage of stations
measuring temperature in a systematic manner. The
records show that since 1850, global average
temperature increased by about 0.8C, with much
of the warming occurring since 1975. -------------
--------------------------------------------------
--------------------------------------------------
----- Philip Brohan and colleagues at
universities in the United Kingdom published this
record of global average temperatures (called
HadCRUT3). The data set was based on a previous
global temperature data set called HadCRUT which
was derived from instrumental records. The old
temperature record was modified to reflect
improvements in estimating sea surface
temperature and land data. The study also
included a comprehensive set of uncertainty
estimates for the data, including estimates of
measurement and sampling error, temperature bias
effects, and the effect of limited observational
coverage on large-scale averages. Brohan, P., J.
J. Kennedy, I. Harris, S. F. B. Tett, and P. D.
Jones (2006), Uncertainty estimates in regional
and global observed temperature changes A new
data set from 1850, J. Geophys. Res., 111,
D12106, doi10.1029/2005JD006548.
25
Proxy Records Temperatures can be deduced from
natural records such as Tree rings
Sediments in the ocean or lakes
Corals Subsurface
rock, soil, or ice temperatures
Layers of ice In Slide Show mode, click
any item above for further information
-------------------------------------------------
--------------------------------------------------
------- The Esper et. al. record was extracted
from tree-ring chronologies from 14 sites in the
Northern Hemisphere. At the time of publication,
Jan Esper and and Fritz Schweingruberwere
affiliated with the Swiss Federal Research
Institute in Switzerland. Edward Cook was
affiliated with Lamont-Doherty Earth Observatory
at Columbia University, New York, in the United
States. Esper, J., E. R. Cook, and F. H.
Schweingruber (2002), Low-Frequency Signals in
Long Tree-Ring Chronologies for Reconstructing
Past Temperature Variability Science 22 March
2002 Vol. 295 no. 5563 pp. 2250-2253 DOI
10.1126/science.1066208
26
Proxy Records Temperatures can be deduced from
natural records such as Tree rings
Sediments in the ocean or lakes
Corals Subsurface
rock, soil, or ice temperatures
Layers of ice In Slide Show mode, click
any item above for further information
-------------------------------------------------
--------------------------------------------------
------- The Mann and Jones record of past
temperatures is based on ice boreholes, ice
cores, sediment records, and tree-ring
chronologies. At the time of publication, Michael
E. Mann was affiliated with the Department of
Environmental Sciences at the University of
Virginia in Charlottesville, Virginia in the USA.
Philip D. Jones is affiliated with the Climatic
Research Unit at University of East Anglia in
Norwich, in the United Kingdom. Mann, M. E.,
and P. D. Jones (2003), Global Surface
Temperatures over the Past Two Millennia
Geophysical Research Letters Vol. 30, No. 15,
1820, August 2003 doi 10.1029/2003GL017814
27
Proxy Records Temperatures can be deduced from
natural records such as Tree rings
Sediments in the ocean or lakes
Corals Subsurface
rock, soil, or ice temperatures
Layers of ice In Slide Show mode, click
any item above for further information
-------------------------------------------------
--------------------------------------------------
------- Anders Moberg and colleagues from Sweden
and Russia published a temperature record deduced
from tree rings and lake and ocean sediments.
Moberg, A., D. M. Sonechkin, K. Holmgren, N. M.
Datsenko, and W. Karlén (2005), Highly variable
Northern Hemisphere temperatures reconstructed
from low- and high-resolution proxy data Nature,
Vol. 433, No. 7026, pp. 613 - 617, 10 February
2005.
28
Proxy Records Temperatures can be deduced from
natural records such as Tree rings
Sediments in the ocean or lakes
Corals Subsurface
rock, soil, or ice temperatures
Layers of ice In Slide Show mode, click
any item above for further information
-------------------------------------------------
--------------------------------------------------
------- Gabriele Hegerl, along with two of her
Duke University colleagues and a collaborator in
the United Kingdom developed their temperature
reconstruction as follows We use large-ensemble
energy balance modeling and simulate the
temperature response to past solar, volcanic and
greenhouse gas forcing to determine which climate
sensitivities yield simulations that are in
agreement with proxy reconstructions. After
accounting for the uncertainty in reconstructions
and estimates of past external forcing, we find
an independent estimate of climate sensitivity
that is very similar to those from instrumental
data. Hegerl, G. C., T. J. Crowley, W. T. Hyde,
and D. J. Frame (2006), Climate sensitivity
constrained by temperature reconstructions over
the past seven centuries. Nature 440, 1029-1032
(20 April 2006) doi10.1038/nature04679
29
Glacier Lengths Historical paintings,
photographs, and other documents enable
researchers to estimate the change in glacier
mass balance over time and deduce corresponding
temperatures. Additionally, dating of plant
materials that were covered by glaciers and
recently exposed provide information about the
timing of changes in glacier lengths. ------------
--------------------------------------------------
-------------------------------------------- J.
Oerlemans of the Institute for Marine and
Atmospheric Research at Utrecht University in the
Netherlands constructed a temperature history for
different parts of the world from 169 glacier
length records. Using a first-order theory of
glacier dynamics, he related changes in glacier
length to changes in temperature. The derived
temperature histories are fully independent of
proxy and instrumental data used in earlier
reconstructions. Oerlemans, J. (2005) Extracting
a Climate Signal from 169 Glacier Records Science
Vol. 308, No. 5722, pp. 675-677, 29 April 2005.
30
Borehole Temperatures Subsurface temperatures
measured in boreholes register not only the
steady state heat flowing out from Earths
interior, but also changes in past surface
temperature. Heat of the Earths atmosphere
diffuses into the Earths crust such that
progressively deeper regions of the subsurface
hold signatures for the temperatures of
progressively older times. More information on
boreholes gt --------------------------------------
--------------------------------------------------
------------------ Shaopeng Huang and a
colleague at the University of Michigan, working
with a collaborator from Canada used present-day
temperatures in 616 boreholes from all continents
except Antarctica to reconstruct century-long
trends in temperatures over the past 500 years at
global, hemispheric and continental
scales. Huang, S.. Pollack, H.N. Shen, P.-Y.
Temperature trends over the past five centuries
reconstructed from borehole temperatures. Nature
403, 756-758 (17 February 2000)
doi10.1038/35001556
31
Borehole Surface Air Temperatures Subsurface
temperatures measured in boreholes register not
only the steady state heat flowing out from
Earths interior, but also changes in past
surface temperature. Heat of the Earths
atmosphere diffuses into the Earths crust such
that progressively deeper regions of the
subsurface hold signatures for the temperatures
of progressively older times. --------------------
--------------------------------------------------
------------------------------------ Robert N.
Harris and David S. Chapman, working at the
University of Utah in the United States developed
a temperature reconstruction using a hybrid
approach that utilized both borehole and surface
air temperature information. Their method yielded
a baseline temperature prior to the instrumental
record suggesting warming of about 1.1C since
1750. Harris, R. N., and D. S. Chapman (2001),
Mid-latitude (3060 N) climatic warming
inferred by combining borehole temperatures with
surface air temperatures, Geophys. Res. Lett.,
28(5), 747750, doi10.1029/2000GL012348.
32
Future Climate Projections Intergovernmental
Panel on Climate Change (IPCC) For its Fourth
Assessment Report released in 2007, the IPCC
considered several possible futures based on
factors including population growth, economic
development, and technological change. Each
scenario was linked to estimates of how the
concentration of greenhouse gases in the
atmosphere would change over time. Twenty-three
different climate models used the scenarios as
input to make projections of global average
temperature through the year 2100. Solid lines
represent the average projection shaded areas
show the range of results. -----------------------
--------------------------------------------------
--------------------------------- In the C3
storyline, CO2 concentrations are held at the
same level as they were in 2000. The projection
indicates that the world will continue to warm
through 2100 due to the lengthy response time of
the climate system. Intergovernmental Panel on
Climate Change (IPCC) (2007), Climate Change
2007 The Physical Science BasisContribution of
Working Group I to the Fourth Assessment Report
of the Intergovernmental Panel on Climate Change,
edited by S. Solomon et al., 996 pp., Cambridge
Univ. Press, New York.
33
Future Climate Projections Intergovernmental
Panel on Climate Change (IPCC) For its Fourth
Assessment Report released in 2007, the IPCC
considered several possible futures based on
factors including population growth, economic
development, and technological change. Each
scenario was linked to estimates of how the
concentration of greenhouse gases in the
atmosphere would change over time. Twenty-three
different climate models used the scenarios as
input to make projections of global average
temperature through the year 2100. Solid lines
represent the average projection shaded areas
show the range of results. -----------------------
--------------------------------------------------
--------------------------------- B1 population
peaks at about 8.7 billion at mid-century, then
declines to around 7 billion at the end of the
century. In this scenario, countries come
together to use both technology and general
environmental controls to decrease emissions,
leading to a temperature increase of less than
2C above the year 2000 level. Intergovernmental
Panel on Climate Change (IPCC) (2007), Climate
Change 2007 The Physical Science
BasisContribution of Working Group I to the
Fourth Assessment Report of the Intergovernmental
Panel on Climate Change, edited by S. Solomon et
al., 996 pp., Cambridge Univ. Press, New York.
34
Future Climate Projections Intergovernmental
Panel on Climate Change (IPCC) For its Fourth
Assessment Report released in 2007, the IPCC
considered several possible futures based on
factors including population growth, economic
development, and technological change. Each
scenario was linked to estimates of how the
concentration of greenhouse gases in the
atmosphere would change over time. Twenty-three
different climate models used the scenarios as
input to make projections of global average
temperature through the year 2100. Solid lines
represent the average projection shaded areas
show the range of results. -----------------------
--------------------------------------------------
--------------------------------- The A1B story
line has population peak around 8.7 billion at
midcentury, then decrease toward 7 billion at the
end of the century. This scenario entertains
efficient technologies with a balance between
fossil fuel and non fossil fuel energy sources.
Global temperature increase in scenario A1B is
2.5C. Intergovernmental Panel on Climate
Change (IPCC) (2007), Climate Change 2007 The
Physical Science BasisContribution of Working
Group I to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change, edited
by S. Solomon et al., 996 pp., Cambridge Univ.
Press, New York.
35
Future Climate Projections Intergovernmental
Panel on Climate Change (IPCC) For its Fourth
Assessment Report released in 2007, the IPCC
considered several possible futures based on
factors including population growth, economic
development, and technological change. Each
scenario was linked to estimates of how the
concentration of greenhouse gases in the
atmosphere would change over time. Twenty-three
different climate models used the scenarios as
input to make projections of global average
temperature through the year 2100. Solid lines
represent the average projection shaded areas
show the range of results. -----------------------
--------------------------------------------------
--------------------------------- In scenario A2,
population increases at current growth rates to
15 billion in 2100, accompanied by a
heterogeneous economic theme of self- reliance
and preservation of local identities. Global
temperature increase with scenario A2 approaches
4C by 2100. Intergovernmental Panel on Climate
Change (IPCC) (2007), Climate Change 2007 The
Physical Science BasisContribution of Working
Group I to the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change, edited
by S. Solomon et al., 996 pp., Cambridge Univ.
Press, New York.
36
Tree Rings (Text from http//www.nap.edu/catalog/
11676.html) Tree ring formation is influenced by
climatic conditions, especially in areas near the
edge of the geographic distribution of tree
species. At high latitudes and/or at high
elevations, tree ring growth is related to
temperature, and thus trees from these sites are
commonly used as a basis for surface temperature
reconstructions. Cores extracted from the trees
provide annually resolved time series of tree
ring width and of wood properties, such as
density and chemical composition, within each
ring. In some cases, records from living trees
can be matched with records from dead wood to
create a single, continuous chronology extending
back several thousand years. Tree ring records
offer a number of advantages for climate
reconstruction, including wide geographic
availability, annual to seasonal resolution, ease
of replication, and internally consistent dating.
Like other proxies, tree rings are influenced by
biological and environmental factors other than
climate. Site selection and quality control
procedures have been developed to account for
these confounding factors. In the application of
these procedures, emphasis is placed on
replication of records both within a site and
among sites and on numerical calibration against
instrumental data. ------------------------------
--------------------------------------------------
-------------------------- Surface Temperature
Reconstructions for the Last 2,000 Years (2006)
Committee on Surface Temperature Reconstructions
for the Last 2,000 Years, National Research
Council. ISBN 0-309-66144-7, 160 pages
http//www.nap.edu/catalog/11676.html
37
Corals (Text from http//www.nap.edu/catalog/1167
6.html) The annual bands in coral skeletons
provide information about environmental
conditions at the time that each band was formed.
This information is mostly derived from changes
in the chemical and isotopic composition of the
coral, which reflects the temperature and
isotopic composition of the water in which it
formed. Since corals live mostly in tropical and
subtropical waters, they provide a useful
complement to records derived from tree rings.
Coral skeleton chemistry is influenced by several
variables, and thus care must be taken when
selecting coral samples and when deriving climate
records from them. Thus far, most of the climate
reconstructions based on corals have been
regional in scale and limited to the last few
hundred years, but there is now work toward
establishing longer records by sampling fossil
corals. -----------------------------------------
--------------------------------------------------
--------------- Surface Temperature
Reconstructions for the Last 2,000 Years (2006)
Committee on Surface Temperature Reconstructions
for the Last 2,000 Years, National Research
Council. ISBN 0-309-66144-7, 160 pages
http//www.nap.edu/catalog/11676.html
38
Ice Cores (Text from http//www.nap.edu/catalog/11
676.html) Oxygen isotopes measured in ice cores
extracted from glaciers and ice caps can be used
to infer the temperature at the time when the
snow was originally deposited. For the most
recent 2,000 years, the age of the ice can in
most places be determined by counting annual
layers. The isotopic composition of the ice in
each layer reflects both the temperature in the
region where the water molecules originally
evaporated far upwind of the glacier and the
temperature of the clouds in which the water
vapor molecules condensed to form snowflakes. The
long-term fluctuations in temperature
reconstructions derived from ice cores can be
cross-checked against the vertical temperature
profiles in the holes out of which they were
drilled (see below). Ice-isotope- based
reconstructions are available only in areas that
are covered with ice that persists on the
landscape (e.g., Greenland, Antarctica, and some
ice fields atop mountains in Africa, the Andes,
and the Himalayas). The interpretation of oxygen
isotope measurements in tropical ice cores is
more complicated than for polar regions because
it depends not only on temperature but also on
precipitation in the adjacent lowlands.
-------------------------------------------------
--------------------------------------------------
------- Surface Temperature Reconstructions for
the Last 2,000 Years (2006) Committee on Surface
Temperature Reconstructions for the Last 2,000
Years, National Research Council. ISBN
0-309-66144-7, 160 pages http//www.nap.edu/catalo
g/11676.html
39
Marine and Lake Sediments (Text from
http//www.nap.edu/catalog/11676.html) Cores
taken from the sediments at the bottoms of lakes
and ocean regions can be analyzed to provide
evidence of past climatic change. Sediment cores
can be analyzed to determine the temperature of
the water from which the various constituents of
the sediment were deposited. This information, in
turn, can be related to the local surface
temperature. Records relevant to temperature
include oxygen isotopes, the ratio of magnesium
to calcium, and the relative abundance of
different microfossil types with known
temperature preferences (such as insects) or with
a strong temperature correlation (e.g., diatoms
and some other algae). Changes in the properties
of sediments are also of interest. For example,
during cold epochs icebergs streaming southward
over the North Atlantic carried sand and gravel
and deposited it in sediments at the latitudes
where they melted the properties of this
material are indicative of the generally colder
conditions in the region where the icebergs
originated. Ocean and lake sediments typically
accumulate slowly, and the layering within them
tends to be smoothed out by bottom-dwelling
organisms. Hence it is only in regions where
sedimentation rates are extraordinarily high
(e.g., the Bermuda Rise, the northwest coast of
Africa) or in a few oxygen-deprived areas (e.g.,
the Santa Barbara Basin, the Cariaco Basin off
Venezuela, or in deep crater lakes) that
sediments can be dated accurately enough to
provide information on climate changes during the
last 2,000 years. More slowly accumulating
sediments from ocean basins throughout the world
are one of our main sources of information on
climate variations on timescales of millennia and
longer. -----------------------------------------
--------------------------------------------------
--------------- Surface Temperature
Reconstructions for the Last 2,000 Years (2006)
Committee on Surface Temperature Reconstructions
for the Last 2,000 Years, National Research
Council. ISBN 0-309-66144-7, 160 pages
http//www.nap.edu/catalog/11676.html
40
Boreholes (Text from http//www.nap.edu/catalog/11
676.html) Past surface temperatures can be
estimated by measuring the vertical temperature
profile down boreholes drilled into rock, frozen
soils, and ice. Temperature variations at the
Earths surface diffuse downward with time by the
same process that causes the handle of a metal
spoon to warm up when it is immersed in a cup of
hot tea. The governing equation for this process
can be used to convert the vertical profile of
temperature in a borehole into a record of
surface temperature versus time. Features in the
vertical temperature profile are smoothed out as
they propagate downward, resulting in a loss of
information. Hence, large-scale surface
temperature reconstructions based on borehole
measurements typically extend back only over a
few centuries, with coarse time resolution.
Hundreds of holes have been drilled to depths of
several hundred meters below the surface at sites
throughout the Northern Hemisphere and at a
smaller number of sites in the Southern
Hemisphere. Many of these boreholes of
opportunity were drilled for other reasons such
as mineral exploration. Specialists acknowledge
several different types of errors in
borehole-based temperature reconstructions, such
as an imperfect match between ground temperature
and near-surface air temperature, but available
evidence indicates that these errors do not
significantly influence reconstructions for large
regions using many boreholes. Boreholes drilled
through glacial ice to extract ice cores are free
from many of these problems and can be analyzed
jointly with the oxygen isotope record from the
corresponding core, yielding a much longer and
more accurate temperature reconstruction than is
possible with boreholes drilled through rock or
permafrost. However, ice-based boreholes are
available only in areas with a thick cover of
ice. ---------------------------------------------
--------------------------------------------------
------------------------------------- Surface
Temperature Reconstructions for the Last 2,000
Years (2006) Committee on Surface Temperature
Reconstructions for the Last 2,000 Years,
National Research Council. ISBN 0-309-66144-7,
160 pages http//www.nap.edu/catalog/11676.html
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