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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,
University of Utah, Salt Lake City, Utah
featuring datasets vetted by the
Intergovernmental Panel on Climate Change
and the National Research Council
In 2006, in response to a request from Congress, the National Academy of
Sciences prepared a report on the state of scientific efforts to reconstruct
surface temperature records over the last 2,000 years.
Because widespread, reliable temperature
records (from thermometers) have only been
available since about 1850, scientists estimate
temperatures in the more distant past by
analyzing "proxy evidence" from tree rings,
corals, ocean and lake sediments, cave deposits,
ice cores, boreholes, and glaciers. To come up
with estimates for past global temperatures,
scientists use sophisticated statistical methods to
combine different types of proxy evidence from
many different locations. These efforts have
resulted in peer-reviewed studies that provide
estimates of global surface temperature for the
last few hundred to few thousand years.
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This presentation shows scientific estimates of global
average temperature from 1000 to 2100. Each
dataset, calculated from instrumental records, proxy
records, or projections made by climate models, has
been published in peer-reviewed literature.
In Slide Show mode, click the name of any dataset
to jump to a slide of additional information
explaining how those temperatures were derived.
Full citations for each dataset are included on the
explanation slides.
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Additional Graphs
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 0.8°C, 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, doi:10.1029/2005JD006548.
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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
Back to Graph
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
Back to Graph
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.
Back to Graph
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) | doi:10.1038/nature04679
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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.
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Borehole Temperatures
Subsurface temperatures measured in boreholes register not only the steady
state heat flowing out from Earth’s interior, but also changes in past surface
temperature. Heat of the Earth’s atmosphere diffuses into the Earth’s crust such
that progressively deeper regions of the subsurface hold signatures for the
temperatures of progressively older times. More information on boreholes >
---------------------------------------------------------------------------------------------------------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) | doi:10.1038/35001556
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Borehole + Surface Air Temperatures
Subsurface temperatures measured in boreholes register not only the steady
state heat flowing out from Earth’s interior, but also changes in past surface
temperature. Heat of the Earth’s atmosphere diffuses into the Earth’s 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 1.1°C since ~1750.
Harris, R. N., and D. S. Chapman (2001), Mid‐latitude (30°–60° N) climatic
warming inferred by combining borehole temperatures with surface air
temperatures, Geophys. Res. Lett., 28(5), 747–750, doi:10.1029/2000GL012348.
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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 Basis—Contribution 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.
Back
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 2°C above the year 2000 level.
Intergovernmental Panel on Climate Change (IPCC) (2007), Climate Change
2007: The Physical Science Basis—Contribution 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.
Back
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 ~2.5°C.
Intergovernmental Panel on Climate Change (IPCC) (2007), Climate Change
2007: The Physical Science Basis—Contribution 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.
Back
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 4°C by 2100.
Intergovernmental Panel on Climate Change (IPCC) (2007), Climate Change
2007: The Physical Science Basis—Contribution 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.
Back
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
Back
Corals (Text from http://www.nap.edu/catalog/11676.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
Back
Ice Cores (Text from http://www.nap.edu/catalog/11676.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-isotopebased 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/catalog/11676.html
Back
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: 0-30966144-7, 160 pages http://www.nap.edu/catalog/11676.html
Back
Boreholes (Text from http://www.nap.edu/catalog/11676.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 Earth’s 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 boreholebased 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: 0-30966144-7, 160 pages http://www.nap.edu/catalog/11676.html
Back
Additional graphs
The following slides present various combinations of the previous
datasets, included here to help users visually resolve and compare
combinations of data.
Presentation prepared by LuAnn Dahlman, NOAA Climate
Program Office
Science Review by David S. Chapman and Michael G. Davis,
Department of Geology and Geophysics,
University of Utah, Salt Lake City, Utah
Educators are welcome to share this electronic file.