Two different approaches were used
Mann et al. (orange line) and two by to estimate temperature, one by Crowley and Lowery (CL blue lines). The black line illustrates the instru mental record of temperature.
Northern Hemisphere Temperature Records (1000-1998)
The USGCRPbudget includes $27 million in FY 2001 for the study of the Earth's amazingly complex climate and environmental history (see Table 9). This element of
the USGCRP focuses on providing a quantitative understanding of how the environment
has changed in the past and defining the envelope of natural environmental variability
within which the effects of human activities on the planet's biosphere, geosphere, and
atmosphere can be assessed.
Paleoenvironmental records are derived from a wide variety of natural archives-
such as: lake and ocean sediments, tree rings, wind-blown deposits, coral, and ice
cores as well as historical documents. Chemical, isotopic, and ecological analyses of
these records have demonstrated that the natural climate system has varied locally and
globally over a far greater range than can be inferred from relatively short-term instru-
mental records. In most locations, instrumental records might provide 100 years of cli-
mate data, whereas an ice core might provide an annual climate record of 10,000 to
30,000 years (more than 400,000 years in Antarctica).
Understanding the natural environmental changes of our planet on long timescales
(years to millennia) provides the context for understanding today's climate dynamics
and elucidating the effects of natural versus anthropogenic influences. Reconstructing
past climate records offers an enhanced understanding of mechanisms that control the
Earth's climate system and, together with insight from numerical modeling exercises,
provides a foundation for anticipating how the planet might respond to future environ-
mental perturbations.
• Recent progress in synthesizing various proxy records of past climates enables
placement of 20th century climate warming within a longer-term perspective.
Recent results indicate that much of the variability during the past 1,000 years prior
to the rise in emissions of greenhouse gases from human activities (beginning in
about 1850) can be attributed to pulses of volcanism or changes in the output of the
Sun's energy. Neither of these mechanisms or natural climate variability in the
ocean-atmosphere system-can explain the late 20th century risc in the globally
averaged surface temperature. Greenhouse gases appear to emerge as the dominant
forcing during the 20th century. According to proxy temperature records, the 1990s
appear to have been the warmest decade (and 1998 the warmest year) in the past
1,000 years.
A partnership between two sets of researchers has resulted in the acquisition of ice
core and meteorological data from the Sajama ice cap in Bolivia. This research has
provided a record of glacial versus interglacial tropical climate dynamics over the
past 25,000 years and is contributing to a better understanding of past and present
tropical Pacific climate variability.
Figure 6. Northern Hemispher e Temperature Records for the Past 1,000 Years (See page 41 for additional information)
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The USGCRPwill focus on acquisition of new paleoenvironmental data, enhancing
paleoclimate modeling, and improving access to both data and models. Goals include:
Constructing new long-term climate and environmental records for parts of North
and South America by successfully obtaining and analyzing eight new long, continu-
ous sediment cores-four from the Great Salt Lake in the United States and four
from Lake Titicaca in Bolivia. This will be accomplished by using a newly acquired
drilling system for obtaining sediment cores from beneath large lakes. These sedi
ments are the primary source of long-term paleoenvironmental records from conti
nental áreas. Acquisition and study of such sediments has been the object of years
of planning and coordination work.
Increasing overall paleoclimate modeling activities by 30-50 percent by improving
computing capabilities and providing model access to additional users. Data-model
comparisons will be an important part of these activities. This paleo-modeling
effort will be complementary to, and compatible with, the extensive climate simula-
tion efforts for modern climate.
Doubling the overall volume of publicly accessible paleoclimate data holdings,
expanding the utility of these data to facilitate their application by a wider range of
users, and expanding data access to 10 percent more users.
INTERNATIONAL CONNECTIONS
The USGCRP addresses an important set of national objectives; it also participates in a
series of international efforts directed toward improving understanding of change on
global and regional scales. The resulting databases, when aggregated, provide essential
inputs to the increasingly complex coupled models that enable scientists to improve
analysis and prediction of global change. Regular interaction between the USCGRPand
these international scientific efforts also results in substantial feedback to our assessment
of the impacts of global change and their consequences for the North American continent.
Some examples of USGCRPinternational connectivity of special relevance for scientific
areas that the USGCRPexpects to emphasize in the coming year are described below.
International Global Change Research Programs
At the global level the International Geosphere-Biosphere Programme (IGBP) has as
its primary goal describing and understanding the interactive physical, chemical, and bio-
logical processes that regulate the Earth system. The IGBP will convene a major
International Open Science Meeting in July 2001 to review the progress of IGBP
research; synthesize results achieved; and set directions for future IGBP research in areas
such as global atmospheric chemistry, global change and terrestrial ecosysterus, and land-
use and land-cover change.
The World Climate Research Programme (WCRP) is directed at improving scien-
tists understanding of the Earth's climate system and climate processes and, through such
studies, determining the extent to which climate can be predicted and the extent to which
humankind influences climate. The WCRP's Global Energy and Water Cycle Experiment
(GEWEX) will be of increasing importance to U.S. scientists as the USGCRPincreasing-
ly emphasizes rescarch on changes in the global water cycle as a primary determinant of
the Earth's climate.
The International Human Dimensions Programme (IHDP) coordinates multidis-
ciplinary international collaborative scientific programs that examine the causes and envi-
ronmental consequences of people's individual and collective actions as well as the
potential efficacy and impact of various general adaptation and mitigation strategies. The
IHDP also works to identify emerging research opportunities and provides synthesis
reports and policy-oriented summaries to contribute a scientific basis for individual and
collective decisionmaking.
Americas, involving nearly 1,000 scientists. The results of IA] projects to date have demonstrated that high-quality, peer-reviewed science, along with capacity building, can produce broad benefits.
The Asia-Pacific Network for Global Change Research (APN) made notable progress in 1999 and was able to increase substantially its support for climate research and studies of the human dimensions of global change. U.S. scientists are substantially involved in APN research programs.
U.S. scientists involved in global change research also work closely with their counter-
parts in many other countries on a bilateral basis. The USCGRP strongly encourages
such direct scientific cooperation. Of special note is the growing cooperation between
U.S. and Japanese scientists in several areas of mutual interest
In 1999, the Seventh U.S.-Japan Workshop on Global Change Research focused
on Precipitation Systems and Their Variability in the Asia-Pacific Region. This work-
shop resulted in several recommendations for follow-up, some of which are being pur-
sued actively this year. The eighth in this series of workshops, which will address
Global Change and Environment, will be convened in November 2000 at NIH. Special
areas of emphasis for this workshop will be climate change and air pollution impacts on
human health, and health impacts of stratospheric ozone depletion and greater exposure
to harmful solar radiation.
International Interactions in Support of Observations and Monitoring
USGCRP scientists are actively engaged in several efforts to expand and improve U.S.
capabilities to observe and monitor the Earth system in support of global change
research. At the international level, the Committee on Earth Observational Satellites
(CEOS) provides a forum through which the United States and other countries that are
conducting Earth remote-sensing programs coordinate their activities. This forum is of
special importance now because of the successful launch of a series of US Earth
remote-sensing satellites in 1999. Cooperative arrangements with the European Space
Agency (ESA) and the National Space Development Agency of Japan (NASDA) also
are valuable in this area.
The Integrated Global Observing Strategy (IGOS) Partnership brings together
CEOS, the International Group of Funding Agencies for Global Change Research
(IGFA); the IGBP and WCRP, and United Nations agencies involved in in situ ocean,
atmosphere, and terrestrial observing systems to promote effective interaction and com-
plementarity between remote sensing and in situ observing systems for global change
research and prediction.
International Scientific Assessment
The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by
the World Meteorological Organization (WMO) and the United Nations Environment
Programme (UNEP) to assess available scientific, technical, and socioeconomic infor-
mation in the field of climate change. A substantial number of USGCRP-supported
researchers are contributing to the IPCC's Third Assessment Report on the science of
climate change; climate change impacts, adaptation, and vulnerability; and mitigation of
climate change.
International Connections
RECENT ASSESSMENTS AND
REPORTS ON GLOBAL CHANGE
Intergovernmental Panel on Climate Change. Climate Change 1993. The Science of Climate
Change Contribution of Working Group I to the Second Assessment Report of the IPCC,
Cambridge, UK: Cambridge University Press, 1996,
Intergovernmental Panel on Climate Change. Climate Change 1995. Impacts, Adaptations and
Mitigation of Climate Change: Scientific-Technical Analyses. Contribution of Working Group
II to the Second Assessment Report of the IPCC Cambridge, UK: Cambridge University
Press, 1996.
Intergovernmental Panel on Climate Change. Climate Change 1995: Economic and Social
Dimensions of Climate Change Contribution of Working Group III to the Second Assessment
Report of the IPCC. Cambridge, U.K.. Cambridge University Press, 1996,
Intergovernmental Panel on Climate Change. The Regional impacts of Climate Change: An
Assessment of Vulnerability. Special Report of the IPCC. Cambridge, U.K.. Cambridge
University Press, 1997,
Intergovernmental Panel on Climate Change. Aviation and the Global Atmosphere. Special Report
of the IPCC Cambridge, UK: Cambridge University Press, 1999.
Intergovernmental Panel on Climate Change Land Use, Land Use Change, and Forestry. Special
Report of the TPCC Cambridge, UK: Cambridge University Press, 2000
Intergovernmental Panel on Climate Change. Emissions Scenarios. Special Report of the IPCC.
Cambridge, UK: Cambridge University Press, 2000.
Intergovernmental Panel on Climate Change Methodological and Technological Issues In
Press, 2000.
Technology Transfer Special Report of the IPCC Cambridge, UK: Cambridge University
National Research Council. Global Environmental Change: Research Pathways for the Next
Decade. Washington, DC: National Academy Press, 1999.
National Research Council. Reconciling Observations of Global Temperature Change.
Washington, DC: National Academy Press, 2000.
United Nations Environment Programme (UNEP) Synthesis of the Reports of the Scientific,
Environmental Effects, and Technology and Economic Assessment Panels of the Montreal
Protocol: A Decade of Assessments for Decision Makers Regarding the Protection of the
Ozone Layer: 1988-1999. Nairobi, Kenya, UNEP, 1999 (Copies of this report are available
from the Web site of the UNEPOzone Secretariat at: http://www.unep.org/ozone or
http://www.unep.ch/ozone)
United Nations Environment Programme (UNEP) Environmental Effects of Ozone Depletion-
1998 Assessment. Nairobi, Kenya: UNEP, 1998. (Copies of this report are available at the fol-
lowing Web site: http://sedac.ciesin.org/ozone/docs/UNEP98/UNEP98.html.)
U.S. Global Change Research Program. A U.S. Carbon Cycle Science Plan Report of the Carbon
and Climate Working Group, 1999.
U.S. Global Change Research Program. 1999 Newly Available Agency Data Sets That are
Significantly Global Change Related. Report of the USGCRPData Management Working
Group. (This report is available on the Global Change Data and Information Systern Web site
at http://globalchange.gov/data/datasets-1999.html.)
World Meteorological Organization, United Nations Environment Programme, NOAA, NASA, and
European Commission. Scientific Assessment of Ozone Depletion. 1998. (This report may be
ordered on the UNEP Web site at: http://www.uncp.org/ozone or http://www.unep.ch/ozone.)
Recent Assessments and Reports on Gloval Chenge
Figure 1: Asymmetric Trends in Arctic and Antarctic Sea-Ice Extent
General circulation model (GCM) experiments that simulate future climate conditions assuming a
gradual increase in atmospheric CO2 show various hemispheric asymmetries in global sea ice
extent. Some suggest that Arctic sea ice will decrease significantly, whereas Antarctic sea ice will
decrease substantially less or even increase. Scientists at the NASAGoddard Space Flight Center
have found observational evidence that there is a current asymmetry in global sea ice changes. In
particular, they found that the areal extent of sea ice decreased by 2.9 +/- 0.4% per decade in the
Arctic and increased by 1.3 +/- 0.2% per decade in the Antarctic from November 1978 through
December 1996. These results are based on measurements from passive microwave instruments on
the Nimbus 7 and three defense Meteorological Satellite Program spacecraft. The assymetry in
sea ice trends is intriguing and indicates that climate in the southern polar region may have very
different dynamics from the climate in the northern polar region.
Source: NASAGoddard Space Flight Center. DJ. Cavalieri, P. Gloersen, C.L. Parkinson, J.C.
Comiso, and H.J. Zwally, Laboratory for Hydrospheric Processes/Code 971.
Figure 2a: Polár ozone loss is now evident in both hemispheres, raising concern that climate change could delay the recovery of stratospheric ozone
Figure 2a is a graph of total column ozono (in Dobson units) as a function of time since 1970, as
obtained from several NASAand NOAAsatellites. The points plotted represent a monthly average
of total column ozone for March in the Northern Hemisphere (NH) and October in the Southern
Hemisphere (SH). The plotted points also represent an average of data obtained from 63 to 90
degrees latitude (defined as the polar region) in each bemisphere. In the SH polar springtine
(October), stratospheric ozone began a steep decline in 1980 that has continued almost smoothly,
leading to steady, severe loss over the last decade. In the NH springtime, the situation is different.
Stratospheric ozone levels were fairly constant during the 1980s, with a significant decline not
beginning until 1990. The NH decline also exhibits greater interannual variability. Both SH and
NH responses are due to the increase in human-supplied chlorine to the stratosphere from ozone-
destroying industrial chemicals now banned by the Montreal Protocol and its amendments and
adjustments. The years with severe NH polar ozone loss are strongly correlated with NH winters of
colder than average stratospheric temperatures, with the cold persisting until the sunlight returns in
the springtime. These are the usual conditions in SH, but until recently have been uncommon the
NH. An emerging explanatory paradigm is that greenhouse gas forcing has been cooling the NH
polar lower stratosphere through dynamical and radiative mechanisms. This interaction of stratos-
pheric chemistry and climate change could delay the expected recovery of stratospheric ozone by a
number of decades.
Figure 2b and 2c: Stratospheric ozone is depleted, as the level of active chlorine (CIO) rises, along the flight track of NASA's ER-2 high-altitude airborne laboratory
Figure 26 and 2c are two plots of measurements made by the instruments on board NASA's ER-2
high-altitude aircraft. These observations were made during field campaigns designed to explore in
detail the health of the stratospheric azone layer in the Antarctic, the Airborne Antarctic Ozone
Experiment (AAOE, 1987), and in the Arctic, the SAGE III Ozone Loss and Validation Experiment
(SOLVE, 1999-2000).
Figure 2b shows ozone and chlorine monoxide concentrations in the lower stratosphere (mumber of
ozone (0) and chlorine monoxide (CIO) molecules per billion molecules of air (in blue and rod,
respectively) plotted against Greenwhich mean time during the AAOE BR-2 flight of September
16, 1987. Chlorine monoxide is the catalytically active radical responsible for severe pofar otone
loss in the polar springtime. As the aircraft flight track crosses into the Antarctic polar vortex, the
concentration of CIO goes up by a factor of 10 while ozone concentration decreases by more the
60% during this same period of the flight. The anti-correlation between ozone and CIO concentra-
tions, exhibited in both the large-scale changes and the smaller fluctuations, is a strong indication
that anomalous chlorine chemistry is responsible for the ozone depletion.
In Figure 2c, a similar plot has been constructed for an ER-2 flight in the Arctic during the SOLVE
campaign conducted on March 11, 2000. Again we see the anti-correlation between ozone and CIO,
this time as the plane flies into the Arctic polar vortex. With advances in measurement capability,
we can now see additional important atmospheric species, chlorine nitrate (CIONO2), the important
reservoir molecule that stores the buman-supplied chlorine in a form not directly destructive to
ozone, and chlorine peroxide (C1,0), the dimer of CIO that is the source of the destructive CIO
when the sunlight returns to the polar regions in the spring. These new observations, a benefit of
technological advances since AAOE, help form a more complete picture of the complex chemistry
of polar ozone loss, and have confirmed that this chemical ozone loss occurs in the Arctic.
Atmospheric chlorine, a result of human emissions, has been available in the atmosphere for many
years, and conversion from the innocuous reservoir forms (such as chlorine nitrate) to the destruc-
tive radical forms (CIO) in the carly polar spring has been a regular feature of springtime Antarctic
chemistry. However, the extremely cold stratospheric temperatures, a necessary ingredient for this
conversion, have also started in recent years to become a more regular feature in the Arctic spring-
time. This development, a possible consequence of increasing greenhouse gases, has the potential
for significant impacts on the larger population of the Northern Hemisphere.
Figure 3: TRMM Measures Sea Surface Temperature Through Clouds
This image was acquired over the tropical Atlantic Occan and U.S. East Coast regions from Aug
22-Sept. 23, 1998. Cloud data were collected by the Geostationary Operational Environmental
Satellite (GOES). Sea Surface Temperature (SST) data were collected aboard the NASA/NASDA
Tropical Rainfall Measuring Mission (TRMM) satellite by the TRMM Microwave Imager
(TMI). TMI is the first satellite unicrowave sensor capable of accurately measuring sea surface ter-
perature through clouds, with results shown in this scene.
For years scientists have known there is a strong correlation between sea surface temperature and
the intensity of hurricanes. But one of the major stumbling blocks for forecastors has boon the pre-
cise measurement of those temperatures when a storm begins to form. In this scene, clouds have
been made translucent to allow an unobstructed view of the surface. Notice Hurricane Bonnie
approaching the Caroline Coast (upper left) and Hurricane Danielle following roughly in its path
(lower right). The ocean surface has been falsely colored to show a map of water temperature-
dark blues are around 75°F, light blues are about 80°F, greens are about 85°F, and yellows are
roughly 90°F.
A hurricane gathers energy from warm waters found at tropical latitudes. In this image we see
Hurricane Bonnie cross the Atlantic, leaving a cooler trail of water in its wake. As Hurricane
Danielle followed in Bonnie's path, the wind speed of the second storm dropped markedly, as
available energy to fuel the storm dropped off. But when Danielle lef Bonnie's wake, wind speeds
increased due to temperature increases in surface water around the storm.
As a hurricane churns up the ocean, it's central vortex draws surface heat and water into the storm.
That suction at the surface causes an upwelling of deep water. At depth, tropical occan waters are
significantly colder than water found near the surface. As they're pulled up to meet the storm, those
colder waters essentially leave a footprint in the storm's wake which might last as long as two
weeks. Forecasters can quantify the difference in surface temperatures between this footprint and
the surrounding temperatures and use that information to better predict storm intensity. If another
storm intersects with this cold water trail, it is likely to lose significant strength due to the fact that
the colder water does not contain as much potential energy as warm water.
Source: TRMM Project, Remote Sensing Systems, and Scientific Visualization Studio, NASAGoddard Space Flight Center
http://earthobservatory.nasa.gov/Newsroom/Newimages/images.php3?img_id-2918
Figure 4: Partitioning of Fossil-Fuel-Derived Carbon
Annual sources and sinks of atmospheric CO, as determined from atmospheric measurements of
CO, and its isotopic ratio CC. Red: fossil fuel combustion; blue: nct uptake by the occans
(sometimes a source), green: net uptake by terrestrial ecosystems (a source due to tropical defor-
estation is included in these numbers); gray: the measured atmospheric increase, which is the sum
of fossil fuel combustion and the exchanges with the oceans and terrestrial biosphere. The atmos-
phere increases every year.
Sources: Francey et al., Nature 373, 326-330 (1995); Tans et al. (private communication), updated
from Ciais et al., Science 269, 1098-1102, (1995); see also www.cmdl.noaa.gov (Carbon Cyclo
Greenhouse Gases).
Figure 5: Potential Change in Wildfire Over the Conterminous U.S. Under Climate Change
The potential change in biomass consumed by fire is shown for two future climate scenarios as
simulated by the MCI dynamic general vegetation model. The future climate scenarios are from
the Hadley Centre (HADCM2SUL) and the Canadian Climate Centre (COCM1). Shown is the dif
ference in the average annual carbon consumed by wildfire over the past 100 years compared to
that simulated over the next 100 years under each scenario. The simulations indicate that climate
change could lead to increased wildfire over much of the western U.S. The green colors show a
reduction in biomass consumed by fire (kg dry matter per m2/yr, while the yellows to reds indicate
an increase in biomass consumed. Both the Hadley and Canadian future climate scenarios produce
increases in biomass consumed in the West, particularly the Southwest and interior dry forests of
the Great Basin. Increased precipitation under both scenarios throughout much of the West pro-
duces more vegetation, which adds fuel to relatively dry ecosystems. Occasional dry years, thus
produce more and larger fires in the drier Southwest and Great Basin ecosystems. Increased
drought stress in the Southeast forested region under the Canadian scenario also results in more and
larger fires in that region. These fire impacts could begin occurring within the next few decades.
MCI (MAPSS-CENTURY, version 1, Daly et al. 2000) is a dynamic general vegetation model,
combining shifting vegetation distribution from the MAPSS biogeography mode! (Mapped
Atmosphere-Plant-Soil System, Neilson 1995) with carbon and nutrient dynamics from the CEN-
TURY biogeochemistry model (Parton ct al. 1987). MCI also contains a state-of- the-art, process-
based fire model (Lenihan et al. 1998), which calculates fuel loads, moisture levels, and wildfire as
a function of climate and vegetation characteristics. These results are for "potential dynamic vege-
tation" only and do not include land-management activities, such as fire suppression, forest harvest,
or conversion to agriculture.
Source: Ronald P. Neilson (USDAForest Service); Dominique Bachelet, James M. Lenihan and
Raymond J. Drapek (Oregon State University).
Bachelet, D., Neilson, R. P., Lenihan, J. M., and Drapek, R. J. (in review), "Climate Change
Effects on Vegetation Distribution and Carbon Budget in the U.S." Submitted to: Ecosystems.
(This journal paper is one of several submitted as a group to Ecosystems as background documents
to the USOCRPNational Climate Assessment.)
Daly C., Bachelet D., Lenihan J.M., Neilson R.P., Parton W., and Ojima D. 2000. Dynamic simula-
tion of tree-grass interactions for global change studies. Ecological Applications 10(2) 449-469.
Lenihan J.M., Daly C., Bachelet D., and Neilson, R.P.. 1998. Simulating broad-scale fire severity in
a dynamic global vegetation model. Northwest Science 72:91-103.
Neilson R.P. 1995. A model for predicting continental scale vegetation distribution and water bal
ance. Ecological Applications 5(2):362-385.
Parton W.J, Schimel D.S., Cole C.V., and Ojina D. 1987. Analysis of factors controlling soil organic levels of grasslands in the Great Plains. Soil Science Society of America 51:1173-1179.
Figure 6: Northern Hemisphere Temperature Records for the Past 1,000 Years
Comparison of different Northern Hemisphere temperature reconstructions for the last 1000 years.
Two different approaches were used to estimate temperature, one by Mann et al. (orange line) and
two by Crowley and Lowery (CL, blue lines). The solid blue line is the best CLestinate, the
dashed line represents an estimate incorporating lower resolution data that are not as reliable. The
black line illustrates the instrumental record of temperature. Regardless of which approach was
adopted, all reconstructions (plus two others for midlatitude summors) agree that late 20th century
temperatures are the highest in at least the last 1000 years.
Source: Figure from Thomas J. Crowley and Thomas S. Lowery, "How Warm Was the Medieval
Warm Period?" Ambio, Vol. 29, No. 1, Feb. 2000, pp. 31-54 (Royal Swedish Academy of
Sciences). Figure also uses data from: (1) Mann, M.E., Bradley, R.S., and Hughes, M.K., 1999,
"Northern Hemisphere Temperatures During the Past Millennium: Inferences, Uncertainties, and
Limitations," Geophys. Res. Lett., 26, 759-762; and (2) Jones, P.D., New, M., Parker, D.B., Martin,
S., and Rigor, L.G., 1999, "Surface Air Temperature and its Changes Over the Past 150 Years," Rev.
Geophys., 37, 173-199.
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