United Statas Of flat of th« Administrator EPA-SAB/EC-S0-0 is
Environmental PftftGOtton Science Advi$ory ioard April 1839
Agency Washington, OC 20460
Report of the Global
Climate Change
Subcommittee
Review of the Report
to Congress:
The Potential Effects
of Global Climate
Change on the
United States
-------
UNITED STATES E\,':RONMENT.V_ "RC "£CTION AGENCY
A A j H I: < •; 7,:;' j D c .: ; j -i.;
April 25, 1§85
The Honorable William K. Reilly
Administrator
u.s. Environmental Protection Agency
401 M Street, S.W,
Washington/ DC 20460
Dear Mr. Reilly:
We are pleased to transmit via this letter the report of the
science Advisory Board"s Global Climate Change Subcommittee
concerning their review of the Agency's first report to congress
on Global Climate Change. This report, The Potential Effects ot
Global climate Change onthe United states, was reviewed by the
Subcommittee on November 17-18, 1988 with comments offered directly
to EPA staff.
The Subcommittee had a number of specific criticisms of the
draft report which have been discussed with EPA staff. These
include suggestions for clarity, reorganization, and areas where
we felt the report could be strengthened such as in the exposition
of methods and results*
It is important to note that although the climate change
effects in' the United states described in this report indicate
potentially serious impacts that are clearly cause for concern on
the part of Congress and the public, we believe that the impacts
do not warrant description as catastrophes threatening national
economic or ecological disaster during the next century. Clearly
we need to improve our scientific understanding of this complex
issue if w* are to plan appropriate strategies to adapt to the
changes or to miter their possible effects.
We regard this report as a good overview of a very complex
subject, suitable for stimulating critical discussion in the United
states and worldwide scientific communities on what science can
tell us about the relationship between the emissions of greenhouse
gases and impacts from potential alterations in climate. we
commend the EPA staff for a good initial effort on the difficult
process of translating the available science into an assessment of
the environmental consequences of global climate change.
-------
We appreciate the opportunity to provide our comments on this
important long-term national and international environmental
problem.
Sincerely,
cc: John Moore
Linda Fisher
Richard Morgenstern
D. Warner North
Chairman
Global Climate Change
Subcommittee
Science Advisory Board
/[Mjyurr-
Rayrfond C. Loehr
Chairman
Executive Committee
Science Advisory Board
-------
ABSTRACT
This report presents the views of the U.S. Environmental
Protection Agency's Science Advisory Board on its review of the
EPA*a report to Congress entitled "potential Effects of Global
Climate change on the united States". The Board regards the
re
-------
NOTIC1
This report has been written as part of the activities of the
Science Advisory Board, a public advisory group providing
extramural scientific information and advice to the Administrator
and other officials of the Environmental Protection Agency. The
Board is structured to provide a balanced expert assessment of
scientific matters related to problems facing the Agency, Shis
report hag not been reviewed for approval by the Agencyt and,
hence, the contents of this report do not necessarily represent the
views and policies of the Environmental Protection Agency or other
agencies in the Federal Government, Mention of trade names or
commercial products does not constitute a recommendation for use.
-------
U.S. Environmental Protection Agency
Science Advisory Board
Global Climate Effects Subcommittee
Chairman
Dr. D. Warner North/ Decision Focus Inc., Los Altos, California
Members
Dr. Stewart Cohen, Canadian Climate Center, Downsview, Ontario,
Canada
Dr. Brian Flannery, Exxon Research and Engineering Co*, Annandala,
Hew Jersey
Dr. Mark Harwell, Center for Environmental Research, Cornell
University, Ithaca, New York
Dr. Margaret Kripke, University of Texas, Anderson cancer Center,
Department of Immunology, Houston, Texas
Dr. Peter Lamb, Climate and Meteorology section, Illinois state
Water Survey, Champaign, Illinois
Dr. William Moomaw, World Resources Institute, Washington, D.C.
Dr. Harold Mooney, Department of Biological Sciences, Stanford
University, Stanford, California
Dr. William Nierenberg, Director Emeritus, Scripps Institution of
oceanography, La Jolla, California
Dr. Martin Parry, Department of Geography, University of
Birmingham, Birmingham, England
Dr. John Reilly, Economic Research Services, tf.s. Department of
Agriculture, Washington, D.C.
Dr. Milt Russell, University of Tennessee, and Oak Ridge National
Laboratory, oak Ridge, Tennessee
Dr. William smith, School of Forestry and Environmental
studies, Yale university, New Haven, Connecticut
Dr. Robert B. Stewart, Agriculture Development Branch, Agriculture
Canada, Ottawa, Ontario, Canada
-------
Dr. Robert Watson, national Aeronautics and space Administration,
Washington, DC
Dr. G. Bruce Wiersma, Idaho National Engineering Lab, Idaho Falls,
Idaho
Executive secretary
Mr. A. Robert Flaak, Environmental Scientist, Science Advisory
Board, U.S. Environmental Protection Afency, Washington, DC
Staff secretary
Ms. Carolyn OSborne, Science Advisory Board, U.S. Environmental
Protection Agency, Washington, DC
-------
TABLE OECONTENTS
1.0 EXECUTIVE SUMMARY ................ 1
2.0 INTRODUCTION ......... , . 3
2,1 Background 4
2.2 Charge to the Subcommittee ........ 5
2.3 Review process and Format of this Report . 5
3.0 REVIEW OF THE EXECUTIVE SUMMARY AND
CHAPTERS 18 AND 19 .............. 6
3.1 Executive summary ....... €
3.2 'Chapter 18 - Research Needs ........ 6
3.3 chapter 19 - Preparation for Global
Warming ......,.., , . s
4,0 REVIEW OF CHAPTERS 1 THROUGH 3 8
4,1 Chapter 2 - Global Climate Change ..... a
4.2 Chapter 3 - Methodology . 9
5,0 REVIEW OF NATIONAL CHAPTERS ........... 10
5.1 Chapter 8 - Water Resources ....*..* 10
S.2 chapter 9 - sea Level Rise 11
5.3 Chapter 10 - Agriculture . 11
5.4 Chapter 11 - Forests 13
5.5 Chapter 12 - Biological Diversity ..... 14
S.6 chapter 13 - Air Quality . 14
5*7 Chapter 14 - Human Health ......... IS
5.8 chapter IS - Urban Infrastructure ..... 16
5.9 chapter If - Electricity Demand ,..,.. 17
5.10 chapter 17 - Variability ......... IS
6.0 REVIEW OF THE REGIONAL CHAPTERS ......... 19
6.1 Chapter 4 - California .......... 19
6.2 Chapter 5 - Great takes .,......,. 20
6.3 Chapter 6 - Southeast ........ ...21
«,4 Chapter 7 - Great Plains 22
-------
1.0 EXECUTIVE STOMARY
The United States Environmental Protection Agency (EPA) has
been asked by Congress to report on the potential environmental and
health effects of global climate change and the choices the global
community may need to consider in order to limit and adapt to
potential global warming. The two reports that EPA is preparing
in response to this request are the Potential Effects of Global
Climate Change OB _the United states and Policy Options^ for
Stabi1i z ing global Climata, The EPA has asked its Science Advisory
Board (SAB) to establish a review panel to evaluate these reports.
The SAB established the Global Climate Change Subcommittee with the
charge to review these two reports and evaluate their technical
adequacy, uncertainties/ and consistency of recommendations with
the findings contained in the reports. This SAB report presents
the conclusions and recommendations of. the Subcommittee on its
review of the first report The Potential Effects of global Climate
chanere_ _ on the United States, (known hereinafter as the Effects
Report).
The Effects Report should be regarded as an overview of a
complex subject/ and it may be most useful as a stimulus to
additional critical discussion in the United states and worldwide
scientific communities on what science can tell us about the
relationship between emissions of greenhouse gases and impacts front
potential alterations in climate. such discussion will help in
refining this initial assessment into a better basis for planning/
and such discussion should also contribute to the education of the
congress and the public on these issues.
In developing its scenarios for climate change in the United
States, the EPA hms relied on projections from three general
circulation models (GCMS). such an approach is a useful way to
assure consistency in methodology for assessing a variety of
impacts in different regions of the country/ but it should be
recognized that the GCMS were never intended for regional
forecasts. The spacing of the grid points is large compared to
the regions examined in the regional case studies, and much
important geographical information relating to local climate is not
included in the GCMs. However, the resulting scenarios seem more
or less consistent with the results from simpler models of
atmospheric circulation and with the consensus among atmospheric
scientists for the potential magnitude of changes in climatic
variables. It is therefore the subcommittee's view that the
methodology the EPA has adopted is a reasonable way to generate
climate change scenarios for an initial assessment of climate
change, and that the EPA has shown an awareness of the difficulties
of interpretation and the uncertainties in the GCK results.
While endorsing the basic approach taken by the EPA, the
Subcommittee believes that the exposition in the draft report of
methods and results could be improved. The Subcommittee has made
-------
many specific suggestions to EPA toward this purpose. The most
significant of these are discussed in this report* Numerous minor
suggestions by Subcommittee members made verbally at the November
17-18, 1988 Subcommittee meeting, or subsequently in their written
comments have already been communicated to the EPA staff
responsible for revision of the draft report, and they will not be
included hare.
In producing the Effects Report the EPA has limited its
attention to the direct effects in the United States. This
limitation is understandable given the time and resources available
to the EPA. However, there may be considerable importance to
effects from climate change outside of the United States. The
United States, as an affluent nation with extensive technological
skills and resources, may be in a better position to deal with the
effects of climate change than many other nations. The indirect
effects on the United States of disruption in other parts of the
world caused by climate alteration may be as severe as any of the
effects portrayed in this report. Further study of impacts in
other countries and their implications for "he United states is an
important task for EPA and other Federal Agencies.
The direct effects of climate change as presented in this
report indicate potentially serious impacts that are clearly cause
for Congress and the public to be concerned. However, these
climate change effects do not warrant description as catastrophes
threatening national economic or ecological disaster during the
next century. In some regions and for some ecological systems the
effects of climate change could be severe, and the Effects Report
indicates where the United states appears to be most vulnerable.
But the magnitude and timing of these effects suggest that a
determined effort should allow the United states to adapt to most
of them, at economic costs that are large in absolute terms but
relatively small if measured as a fraction of the United states
economy over a time period of fifty years to a century* This
conclusion is necessarily weak, because the current scientific
understanding of the global climate system and the consequences of
climate change is so limited. There is a clear and immediate need
to improve our scientific understanding* The Effects Report
suggests that global climate change presents the United states with
a problem that is substantial in terms of its potential demand for
planning and for economic and technical resources, but not
overwhelming in magnitude compared to the other long-term national
and international problems that Congress must address in the last
decade of this century.
The EPA should be commended for a good initial effort on the
difficult process of translating the science into a beginning of
an environmental assessment* The draft Effects Report meets the
goal of summarizing available information into an overview of how
global climate alteration could affect the United states. As far
-------
as the Subcommittee is aware, it is the first major national
effects study of its Kind.
2*0 INTRODUCTION
There is an emerging consensus in the scientific community oa
the importance of global climate as an issue deserving attention
by policy makers in the United states and other nations, on the
basis of past anthropogenic activities and those foreseeable within
the next several decades/ it seems likely that global climate may
be altered. While warming is expected, the character, magnitude,
and timing of the alteration in climate ace highly uncertain. It
is not possible with existing scientific information to make
precise predictions of either global or regional impacts that nay
occur as the result of the increased loading in the atmosphere of
carbon dioxide and other greenhouse gases. The climate inpacts of
greenhouse gases could be significant, and early planning nay help
to mitigate or avoid adverse effects associated with climate
change.
It is, therefore, appropriate for the U.S. Federal Government
to begin the assessment and planning process. The subcommittee
regards the request by Congress for the EPA to prepare an initial
assessment of the potential effects of global climate change as
reasonable and timely. The expectations for this initial
assessment should be modest since this is an effort to characterize
an exceedingly complex issue that cuts across a large number of
academic disciplines. What the assessment can do is to indicate
the relationships between emissions of greenhouse gases, changes
in the atmosphere and climate that may result, and potential
changes in hydrological, biological, and economic systems that are
sensitive to climate. We cannot expect that this Effects Report
can provide us with predictions of what climate changes may occur
and how these changes will affect the United States. Rather the
Effects Report examines a set of scenarios that are intended to
represent possibilities for future climate change. By examining
the consequences associated with these scenarios, th* EPA has
attempted to explore a wide range of potential impacts from the
climate alteration on both a national'and a regional basis, in the
Subcommittee's judgment the usefulness of this effort is in
providing a 'first iteration - a point of departure for additional
research on these issues and for beginning a planning process by
the Federal Government.
Some may contend that the uncertainties in predicting the
extent and character of the climate changes are so large at this
time as to make such as assessment of little value. The
Subcommittee believes that the assessment and planning process
should not be deterred by the large uncertainties, which arise in
large measure from our lack of understanding of natural variations
in climate. In the Subcommittee's judgment, there is a broad
-------
scientific consensus on the type of climate change that could occur
from alteration of the composition of the atmosphere. Such
alteration of the levels of carbon dioxide and other trace gases
affecting the earth's radiative balance is clearly demonstrated in
the data, and these alterations can be expected to accelerate in
the next century as the result of population growth and energy,
forestry, agricultural, and industrial practices in all the
countries of the world. The extent of these practices, and their
implications for'emissions of greenhouse gases, can be estimated
with fair precision using available methods*
what are not available now are methods for predicting natural
variations in climate and understanding the complex ocean-
atmosphere interactions that determine the earth's climate, we are
unable to predict weather more than a few days in advance, and we
are just learning about the causes of shifts in the world's weather
patterns, which have occurred throughout recorded history and back
through geological time. At this time, our most advanced general
circulation models (GCMs) may give us little better predictive
capability than simple radiation balance calculations showing he-'
increasing levels of greenhouse gases will cause a warming of the
earth by absorbing infrared radiation that would otherwise be
radiated through the atmosphere and out into space. We do not have
the predictive capability to assess how increasing levels of
greenhouse gases will alter atmospheric circulation, and we have
far less confidence in predicting regional climate impacts than in
predicting that increasing levels of greenhouse gases will lead to
global aggregate warming. Since we have little ability to predict
the natural fluctuations in climate, we cannot rule out the
possibility that a natural cooling trend may offset the warming
induced by greenhouse gases over the next several decades. We also
cannot rule out the possibility of larger temperature increases
than those predicted by the models currently available, changes
in regional precipitation and in the frequency of extreme
meteorological events are even more difficult to predict than
temperature changes with our current level of scientific
understanding.
2.1 Background
In early 1988, the EPA's office of Policy, Planning and
Evaluation (OPPE) requested that the science Advisory Board (SAB)
establish a review panel to examine the two EPA reports to congress
on global climate change. These are The _ Potential Effects of
Global _ Climate Change on the onited states (Effects ReportJ and
Policy options for Stabiliiino:...Global Climate (Stabilizing Report) .
Based on this readiest, the SAB established the Global Climate
Change Subcommittee as an ad hoc subcommittee of its Executive
Committee. The first of these EPA reports, the Effects Report, was
provided to the Subcommittee in October 1988, with the review
meeting held on November 17-19, 2,988 in Washington, DC. The
-------
Stabilizing Report is scheduled for release to the subcommittee in
March, 1989, with subsequent public review April 4-5, 1989. The
Subcommittee will provide a separate report on its review of that
document.
2.2 Charge to the Subcommittee
The subcommittee has been tasked with the responsibility to
review the two EPA reports to Congress and to provide advice to
the Agency on the following;
Assessment of the technical adequacy of the two reports,
especially the degree to which they address the
environmental and other effects of climate change.
Identification of areas of uncertainty in the reports,
and the degree to which this uncertainty may affect the
recommendations.
- Consistency of the recommendations with the findings
contained in the reports. Specifically (for tie
Stabilizing Report), are policy options identified that,
if implemented, would stabilize current levels of
atmospheric greenhouse gas concentrations.
Other related issues that the subcommittee believes
should be addressed.
2,3 Review Process and_Format of this Resort
The Subcommittee's task was to review the draft Effects Report
and to provide advice to iPA on means to improve the report, not
to provide ongoing oversight of the document as it may evolve from
the point of the review. At the November 17-18, l§88 meeting, the
Agency staff were provided with detailed comments on each chapter
of the report. Following the meeting, they were provided with
detailed written comments and a transcript of the meeting.
This report contains information compiled from the meeting
transcript and from written comments submitted by each subcommittee
member. ' Editorial items are generally omitted since they have
already been provided to EPA. The subcommittee's primary goal is
to summarize the main points of our advice to EPA, not to reiterate
all the advice given to EPA at the public meeting and in our
written comments.
This report contains six major divisions? an Executive Summary
which highlights the major issues we wish to emphasize; an
Introduction which provides a discussion of broader issues along
with the background and purpose of this review; and four sections
-------
which review the individual chapters of the Effects Report by
groups. The first of these sections (3.0) contains our review of
the Executive Summary and chapters is and 19; the second section
(4,0) contains our review of Chapters I through 3y the third
section (5,0) contains our review of Chapters 8 through 17; and the
fourth section (6.0) contains our review of chapters 4 through 7.
We have suggested some reorganization of the chapters and our
comments will follow these suggestions while referencing the
chapter numbering used in the draft Effects Report.
3.0 REVIEW.OP THE EXECUTIVE SOMMARY RHP CHAPTERS 18AND 19
This section contains our review of the Executive Summary/
chapter 18 - Research Needs, and chapter 19 - Preparation for
Global Warming, These three chapters were grouped since they
represent the major summary and recommendations of the Effects
Report,
3.1 Review of the Executive Summary
This chapter covers a vast amount of material, and as such,
loses the clear and concise style expected in an executive summary,
We found the length to be excessive, even for a document of the
size and complexity of the draft Effects Report. Moreover, the
summary did not always cover the most critical issues, nor did it
provide all the necessary caveats. The Executive summary needs a
more balanced tone, indicating that the potential effects in the
United States are significant, but that they do not appear to be
catastrophic and unmanageable. In addition, the Executive summary
should contain the uain ideas from Chapter if. More focus on the
relevance of information on effects for decision-making may help
to make the Executive Summary more concise and to integrate its
insights with those from the Stabilizing Report.
While EPA has strived to write a comprehensive, balanced
assessment of potential effects that could result from a change in
climate, the inconsistent use of language will almost certainly
lead to misrepresentation, especially by readers who see only
excerpts from the text. While the draft frecently states that the
assessments are only scenarios and are not meant to be predictions
of the future, this message is often muddled by the use of language
such as "will occur". The Executive Summary should strive for more
consistent and concise wording describing the objectives and
conclusions of the Effects Report.
3»2 Review .of _Chaj>ter JL8_^ Regearch_Needs
This chapter should include a clearer statement of research
needs for better prediction of climate change at the regional
-------
level, and better quantification of the consequences of any such
climate change. The chapter should not discuss which agencies
should be responsible for different aspects of the needed research;
rather, reference should be made to other documents, such as tha
report of the Committee for Earth sciences (1989) and the research
program description being prepared by SPA'S office of Research and
Development. The chapter should address the issue of inter-agency
coordination both for science and policy. There should be explicit
acknowledgements of the United States Global Climate Change Program
and the International Geosphere-Biosphere Programme.
The section on atmospheric research needs was well written
and well thought out, with clearly defined discussions of the
uncertainties in our understanding and clearly posed research
questions. Similarly, the discussion of the scenarios-assessment
methodology was well done. This methodology offers a reasoned
approach to assessing potential climate effects and policy
implications, in contrast, there were a number of areas in which
we felt that the ecological research discussions were deficient,
our suggestions for improvement in this area are identified is our
detailed written comments that were submitted earlier.
The issue of integrated regional assessment is a tremendous
research challenge. It will require the construction of a regional
framework of linked models which by necessity nust include regional
economic models. Research on the linkages between environmental
changes and economic changes needs to be a high priority. At
present, economic changes are considered only in individual sectors
(e.g. agriculture). Greater involvement of economists and policy
analysts in effects research should be encouraged.
General circulation models appear to be a paradigm for
producing necessary information for impact assessment. However,
this chapter points out current major limitations of GCMs. To
date, GCMS provide uncertain predictions for an incomplete subset
of the required variables. Therefore a major component of the
research should involve specifications for the types of information
needed, and programs of model validation to assess the reliability
of the GCM results* It is important that such model validation (a)
identify strategies and (b) acquire data both to demonstrate the
extent to which climate change is occurring, and to calibrate the
behavior of the models*
Both for impact assessment and for the evaluation of policy
options for stabilization, EPA ought to have' in place its own
mechanisms to assess the reliability of model information and the
sensitivity of conclusions to uncertainties in model data mnd
structure* Since model results involve substantial scientific
uncertainty, it is important to estimate when effects ought to be
observable, and to confirm them by direct observation as soon as
possible.
-------
3.3 Revieir of chapter 3.9 _- Preparation for Global warming
w* found this chapter to be very strong, it appears to have
been written very carefully, with proper consideration of
scientific uncertainties, and it raises a broad range of questions
that cut across disciplines. Because of its focus on decision-
making, it is an appropriate closing chapter. However, since it
is preceded by a discussion of research needs (chapter 18), the
reader may see this as being somewhat similar. Chapter is becomes
a shopping list for "scientific" research, while Chapter 19
provides at list for "policy" research.
In our review of Chapter 3.8, one complaint was that regional
(or national) environment-economy linkages was not an explicit part
of the research list. Many of the questions asked in chapter 19
require consideration of these linkages, otherwise, the "strategic
assessments" use *«old" economics to answer new questions. The
chapter points out that cost and profitability may be important
factors in decision-making, and that the cost of doing nothing may
be greater than anticipatory action. But there are advantages and
disadvantages to using benefit-cost, input-output, econometric or
other methods in performing these assessments, and there has been
no attempt in this chapter or chapter 18 to identify and discuss
these methods*
This chapter reflects the kind of "tone11 in language towards
which the rest of the report should move. Prolific use of examples
in this section is useful in enhancing understanding. In addition,
the notion of "de-centralized11 decision-making relative to climate
change planning is appropriate. We believe that the entire report
should be carefully edited to be consistent with the message of
this chapter.
4,0 aBVTEW OF CHAPTERS 1 THROUGH 3
The material contained in chapter l (introduction) provides
a brief description of the charge given by Congress to HA, a
description of the goals and scope of the Effects Report, a history
of the process by which the report was produced, and a brief
discussion of related national and international activities on the
assessment of global climate change. This chapter was not
specifically reviewed by the subcommittee, other than to ensure
consistency with other portions of the draft Effects Report, our
comments regarding the scope of the Effects Report have been given
above in the Executive summary,
4.1 Review of Chapter 2. - global climate change
This chapter is a summary of scientific information about
global climate change intended to provide the reader unfamiliar
-------
with this subject with sufficient technical background for the
remaining chapters of the Effects leport. The Subcommittee found
the chapter to be in need of substantial rewriting, both for the
expository style and to correct specific technical problems. The
chapter contains material that is misleading or technically
inaccurate, and the specific problems have been described in the
Subcommittee's earlier comments to EPA. The chapter needs to
communicate key elements of the scientific information about global
climate change in a journalistic style that sets forth clearly and
simply the major scientific data and areas of uncertainty. The
following are key points that should be emphasized;
a) Trace gas concentrations are increasing, and they are now
above previous historical maxima,
b> These gases are infra-red active, so that they perturb the
radiative balance of the atmosphere.
c) There is evidence suggesting an increase in atmospheric
temperatures, but the magnitude of the increase is uncertain, and
the observed pattern of changes over time to date differs from the
model predictions. sea surface temperatures are not fully
consistent with the air temperatures*
d) Knowledge about key climate feedback processes, such as the
role of clouds and the exchange of energy and gases between the
atmosphere and the oceans, is quite limited.
e) The general circulation models (GCMs) are limited in their
ability to predict regional climate and climate changes.
f) The fact that we cannot accurately predict the magnitude
and rate of climate change is cause for concern.
*»2 Reyieir_of jghajjrtejr^S^- Methodoloqry
This chapter describes the GCM runs that were used by SPA.
The model calculations should be viewed as highly uncertain, since,
as EPA notes, the models do not adequately incorporate the role of
oceans in controlling global climate, or the role of clouds in
modifying regional climate changes. The chapter does a good job
of placing OCM results in their proper context, including most of
the necessary caveats. However, the rationale for using the three
GCM outputs should be better articulated. It is essential that the
chapter not try to defend the ability of GCM's to predict regional
climate changes. While the GCM's are mathematically consistent,
they may not represent a true climate consistency. SPA should show
that they recognize that the range of climate changes predicted by
the models may not encompass the actual changes that may occur.
-------
some added discussion concerning general circulation model
verification would be useful. This involves availability of data
and the development of strategies to reconcile, tune, and validate
the models. Description of the assumptions used in the three major
GCM's is lacking, and the report does not include specific outputs
from these models. This information is needed to help readers to
assess the validity of many of the conclusions in the Effects
Eeport, which are based on results from the GCMs. in addition, the
methodology discussion is confusing, because it is not clear if the
same GCM runs were used for all the assessments. If not, the
scenarios need to be clearly stated for each assessment area.
Although the EPA authors note that the coarse grid resolution
of the GCMs makes their application to state-level effects analyses
problematic, the limitations of the poor spatial scale of the GCM'S
should be acknowledged and discussed in more detail. The chapter
should also discuss the specific limitations of the transient
model. The GZSS case ft and B scenarios should have more discussion
in light of the Montreal protocol. In addition, more discussion
using the 3,$SQ-198Q 30-year record of variability is needed. The
sensitivity of the results to this particular period is a key point
for the discussion.
5.0 REVIEW OF NATIONAL CHAPTERS
5.1 Review of chapter 8; Water Resources
This chapter is viewed by the Subcommittee as a solid effort,
requiring only modest revision. The discussion is policy oriented,
focusing on economic and legislative aspects of United States vater
resources management and how these might have to change in response
to elimace change. The list of research needs reflects this
orientation; these research needs are reasonable if one is not
concerned about specific scenarios of climate change. The change
in seasonal!ty needs greater emphasis* The background material is
authoritativei' the key role of temperature increase is essentially
independent of scenariosI the range of studies commissioned and
used is adequate; and the treatment of impacts and their policy
implications is also satisfactory. There is enough material in
this chapter to provide ample food for thought to policy
researchers and analysts, as well as Federal, State, and local
government agencies concerned with water resources.
We note that there are no recommendations regarding hydro logic
and water resources modeling. This could be misinterpreted that
we know all the answers on issues such as climate/water demand
relationships, effects of CQ2 enrichment on plant water use, or
projections of runoff for specific watersheds that have not been
done in this work (e.g., .Great Plains and Tennessee Valley
Authority (TVA) basins). Overall, caveats should be added to avoid
the possibility of such misinterpretation.
10
-------
We concur with the recommendation to integrate drought
planning into water resource management (page 8-30). Water
resource impacts, particularly groundwater, may be the largest
potential cumulative problem in climate warming for North America*
A means of prioritizing this and other potential effects for
possible severity and human or biological resource impact would be
useful.
S.2 Review of Chapter 9 - sea Level Rise
The chapter provides a good summary of today's knowledge and
experience. It covers a wide spectrum of effects in a very
competent series of analyses, including discussions of limits and
constraints. The authors clearly describe the scenarios used and
the application of the scenarios is consistent!* discussion
includes analysis of possible responses and potential conflicts,
particularly coastal protection vs. wetland loss. Research needs
are not restricted to the technical aspects of coastal erosion,
but also include modeling and monitoring of climate change.
The effect of increased sea levels on bars/ beaches and
wetlands is comprehensively dealt with, except for the almost
unpredictable action of waves on beaches. We have much experience
from hurricanes as to the capriciousness of wave action* During II
Nino there was a twenty centimeter rise in the ocean level at La
Jolla, California; data 'from such episodes of sea level change
could give clues as to the reality of predicted effects. Recent
analyses by Bassett and others indicate that in some areas an
increase in ocean temperature was not accompanied by a
corresponding rise in height*
The policy analyses in this chapter are weak and do not make
a significant contribution. We recommend these sections be
strengthened or deleted. The financial figures for protecting
developed coastal areas against sea level rise are impressive, but
the expenditures suggested are spread over 100 years. On an annual
basis, the rate of expenditure is estimated to be approximately a
billion dollars per year. Compared to the amount already being
spent on coastal stabilization each year, that figure is not large.
However, th« central point is that leadership, education, and
coordination are needed to manage these financial expenditures
wisely.
S.3 Review of chapter 10 - Agriculture
The chapter presents an excellent summary of the sensitivity
of agriculture to changes in climate. The objectives and the
limitation of the studies undertaken by the EPA on agriculture are
clearly stated. The discussion of potential direct CO2 effects on
crop yields is very good. The methodology and limitations of the
11
-------
regional and national studies are well defined, and the results and
implications are ?juite explicit.
The chapter on agriculture includes & range of studies, not
only of the effects of climate change and of increasing atmospheric
CO2 on crop yields, but also of possible changes in cropping
patterns that may result from farmers responding to the
differential pattern of yield changes and the land use shifts that
nay flow from these yield changes. In addition, consideration is
given to possible changes in irrigation requirements,
infrastructure changes in the agricultural sector, the adoption of
new agricultural technologies and management systems, effects on
pests and diseases, possible changes in pesticide and fertilizer
use, and the implications of these for the ecology of the farmed
areas. In addition, the authors point out implications for the
price of agricultural products both in the United States and
overseas. They emphasize that changes in productive potential in
competing food-producing areas outside the United states will be
important, both for agricultural exports and for domestic food
prices* To expect a comprehensive and quantitative statement of
all these possible effects is unrealistic but, overall, the authors
have succeeded in presenting a balanced, partially quantified
statement of the wide range of potential effects that nay accrue
both in the agricultural sector and in related ecological and
economic regimes.
The results presented in the chapter should be balanced by
three considerations that merit additional discussion;
a) The global nature of climate change - She chapter notes
that agriculture will be affected globally. 21 stronger indication
of the types of effects in other countries could be made. For
example, warming may enhance the agricultural capabilities of the
U.S.S.R. While the net effect of climate change on the rest of the
world is uncertain, the global effects could overwhelm in
importance the effects in the United States. A net negative effect
on agriculture could improve the position of united States
agriculture producers through enhanced exports, but adversely
affect u.8. consumers through increases in global commodity prices.
b) £cj;ential benefits - Unlike many environmental concerns
where impacts are clearly adverse, climate change offers
opportunities for benefits as well as costs. The chapter
identifies potential benefits of CQz-induced climate change, such
as co2 fertilization and longer growth seasons in northern areas*
A focused effort to identify potential benefits of climate change
would be a major contribution toward determining appropriate
adjustment policies.
c) Timing - The element of timing is not treated directly in
the agricultural study. When will a doubling occur? If warming
occurs rapidly, will there be greater costs? Do the agricultural
12
-------
coats of more than doubling rise linearly, or at an increasing
rate?
In general, economic and policy implications and agricultural
research needs are clearly set forth in this chapter* However,
there are some significant omissions. Except for soil erosion,
there is little discussion concerning the impact of climate change
on the resource base* There is no mention of current soil
degradation problems or the possibility that climate change might
exacerbate these problems. Another significant omission concerns
the potential implications of changes in population dynamics on the
agricultural system, both in terms of increasing demand, and for
pressures that will be put on the resource base to meet future
population increases. changes in population dynamics also have
major implications for water use, water quality, and environmental
impacts. Future studies involving climate change certainly should
incorporate changes in population into the scenarios developed.
S.4 Review of Chapter 11 - Forests
This chapter seems to be a reasonable, well-written summary
of potential effects on forests. It appropriately stresses the
uncertainties associated with our lack of knowledge about migration
rates of plant species, mitigating effects of elevated CQ2,
possible changes in frequencies of fires and other disturbances,
and unknown impacts on competition and how various stresses
interact to determine forest community composition. The discussion
is always in terms of "may11 and "could", in recognition of the fact
that we do not know how climate will change, The chapter
repeatedly emphasizes the complexities and uncertainties involved
in projecting effects on forests. It is .clear that if the climate
changed as much as the models predict, the effects on forests could
be dramatic. The multiple implications for timber .production,
recreation, and environmental quality are objectively noted.
The conclusions in the chapter should be better supported.
The chapter should state more explicitly what climate change
scenarios were used. There is too much reliance on the unpublished
reports by the EPA contractors, and the limitations in those
contractor reports are not adequately presented. For example, the
remarkable rapidity of forest changes in the Great Lakes region
suggested by the forest modeling of Botkin et al* may be correct,
but the tinting fundamentally depends on the moisture-stress-induced
mortality for adult tree species. This mortality is difficult to
measure, and the sensitivity of the cited results to the mortality
should be explicitly stated in the chapter, similar caveats may
apply to the conclusions on the rapidity of species changes in the
southeastern and western forests, which also are indicated to have
rapid species shifts from climate change. More supporting
information from the technical studies should be included in the
chapter.
13
-------
5.5 Review of chapter 12 - Bio_logjLeal_.Diyer8_i.ty
It is clear that the rates of change are central to
understanding impacts. In this chapter, there isn't a sufficient
attempt to place the findings into the general framework of hew
fast changes occur, as a result, this chapter is very mixed. Much
of the discussion in the chapter is general, since there are few
specific case studies to draw on,'and therefore, few quantitative
estimates of impacts are presented. Important problems have been
identified, including management of reserves during climate change.
Research needs include a number of fundamentals, such as
identification of species and the influence of CO2 enrichment.
Several specific findings that we wish to highlight are the
following:
a) varying definitions for "biological diversity" throughout
the chapter lead to . confusion. Zn some eases it is a narrow
concept of species diversity, and in others it is the broad
definition encompassing species diversity, genetic diversity, and
ecosystem diversity. Usage of this term should be made uniform
throughout, hopefully, utilizing the latter broad definition.
b) There is a misuse of the concept of adaptation. What is
implied here is that species can adjust to change through
dispersal, etc. Species are not changing their genetic
constitution necessarily in order to do this. The term adaptation
implies such a genetic adjustment.
c) it appears that only aquatic studies were conducted for
this report (Table 12-1), when most of the discussion in the text
concerns terrestrial areas. This balance needs correction.
Overall, the findings and the discussion of the value of
biological diversity seem adequate. Section III, Components,
provides clear definition and perspective. Section XV, Factors
Influencing Diversity Response to Climate Change, tends to
oversimplify the complexity and uncertainty and focuses primarily
on "barriers" to response, which may not be the most important
factor. Section V, Effects, and Section VI, National Policy, are
adequate. In Section VT1, Research Meeds, the need for additional
information on current diversity is emphasized. Other research
goals seem less clear. Perhaps some mention to EPA'S Scoregion
concept, and opportunities to use this strategy to predict changes
in ecoregion boundaries from climate change, would be appropriate.
5.6 Reviewof Chapter 13 - Air Quality
this is a useful, generally well-written review of issues,
particularly linkages between climate change and air quality
(including acid rain) and implications for National Ambient Air
14
-------
Quality Standards (NAAQS), Research needs include modeling and
policy analysis. The chapter concludes tbat there is a likelihood
of increases in concentrations, or number of exceedances of
standards, for criteria air pollutants as a result of predicted
climate change during the next several decades. The presumed
climate change may result in increased occurrence of stagnation
and clear-sky high-pressure systems, increased surface air
temperatures, higher levels of ultraviolet (W) light, and higher
emissions of pollutants or precursors as energy demand goes up with
temperature.
Regional modeling studies were carried out for central
California and for the midwestern/southeastern United states, using
a model of regional transport and photochemistry, RTM-III, and an
assumed scenario of increased temperatures, comparisons with runs
using currently-observed temperatures showed an increase of up to
20% in maximum ozone levels in central California. in the
midwest/southwest region, the increase in the maximum ozone level
was insignificant (4%). In both cases, the areas predicted to
exceed national ozone standards increased substantially (nearly
doubling and tripling, respectively). some interpretation is
provided of possible regulatory implications for these scenarios.
For example, areas that just attain national ambient standards for
ozone currently may find themselves exceeding the standards if
temperatures increase.
Deposition of acidic gases and aerosols may be altered by
climate change, but no calculations of the magnitude of these
effects are reported in the chapter. Since the GCM
parameterizations of the surface and boundary layer are crude at
regional scales, few firm conclusions on these pollutants are
possible at this time. Potential linkage of GCMs with regional
models that contain details on air chemistry might be a useful
research direction, to look not only at regional climate but also
changes in ozone, acidic gases, and aerosols. Throughout this
chapter there should be more detailed information on the basis of
the calculations, and a discussion of uncertainty factors like
increased cloudiness and increased daytime mixing height:*
5*7 Review of_chaBter 14 - Human Health
This seems to be a reasonably comprehensive and clear analysis
of the potential impacts of global warming on human health in the
United states* The discussion is interesting, though very little
is presented on cold weather illnesses (e.g. influenza). Winter
will be very different in northern areas that now experience
several months of snow. what will happen if northern winters
become warmer (and wetter?) with rain replacing some or most of the
snow1? There are other potentially important omissions, and there
is a need to be more specific in the use of certain terms to
enhance the clarity of this chapter,
3.5
-------
A major omission concerns the indirect impacts of global
warming on the United States. The primary effects of global
warming on human health will occur outside the United States in
underdeveloped countries because of their inability to take
adaptive or preventive measures* External health effects will have
an impact on our country by means of our participation in
international aid and relief programs and from the potential for
introducing diseases into the United States through travel,
immigration, and disease vectors. In fact, one of the potentially
most serious consequences of global warming may be the escalation
of international tensions as a result of diseases/ flooding, or
water and food shortages in other parts of the world. To ignore
these indirect effects on the United States seems quite remiss, not
only in the area of health effects, but in the other areas as well.
We strongly urge that the international implications of global
warming be included in this document where appropriate because they
are likely to have important political, economic, and health
consequences in our country.
A second omission is a consideration of possible increases in
mortality from cataclysmic weather-related events, such as floods,
tornados, cyclones, etc* If such events increase as a result of
warming, their associated mortality will also increase, ferhaps
this would represent a very small contribution to national
mortality figures, but internationally, it could have serious
consequences, which would affect the U.S. indirectly.
There is great imprecision in the description of weather-
related illnesses* An increased effort should be made to specify
the nature of particular relationships to weather. For instance,
are weather-relates summer deaths or illnesses due to increased
average temperature, increased season length, increased frequency
of high temperature extremes, increased humidity, or increased
smog? There is also a lack of precision in the discussion of the
various illnesses. The chapter should distinguish between
increased incidence* morbidity, and mortality whenever possible,
More emphasis should be given to the idea that the groups at
greatest health risk from global warming are the poor, the elderly,
and infants. These are the persons least able to adapt to
environmental changes, and hence they will bear the brunt of the
effects on illness and mortality.
5-8 Review of Chapter 15 - Urban infrastructure
This chapter is well-written, and in some respects* one of
the most important contributions in the report. The case studies
on three United states cities provide a valuable set of insights
on the impacts and potential adjustments by U.S. cities to climate
change. These case studies indicate the need for planning, but
viewed in the context of the massive expenditures on urban
16
-------
infrastructure over a period of 50-100 years as this infrastructure
is renewed, the incremental expenditures resulting from climate
change appear very small.
The policy discussion is very useful/ even though it is based
on only a few case studies. Mere case studies of other U.S. cities
are clearly needed. The challenge will be to encourage direct
involvement by state and municipal agencies in research and
planning efforts. So far, these efforts have been confined largely
to federal agencies.
5-9 Review of chapter 16 - Electricity Demand
This chapter needs a qualitative discussion at the beginning
that looks more broadly at potential impacts on the energy sector.
The existing discussion is mainly centered on utilities, and it
should briefly review the non-utility energy impacts and state the
reasons for focusing on electric utilities. In reviewing utility
impacts, more discussion is needed on loss of hydro, population
shifts, cooling water loss, pumping for irrigation, pumping for
coastline management, and other potential changes affecting
utilities and energy producers.
The effect of planning for climate uncertainty should be
noted. The conclusions regarding the need for additional
generating capacity seem to imply that the only energy alternative
is more fossil fuel power plants. The nuclear option is never
mentioned.
The role of energy conservation could be discussed in more
detail. Conservation is important as a stabilizing strategy, to
be discussed at length in the next report, but in the context of
demand projections it should be acknowledged. The magnitude of
the impact of climate change in increasing electricity demand
appears small relative to uncertainty in demand growth and in the
replacement of existing capacity with new generating equipment over
a ?o year period* However, at the regional level, climate change
could have an important impact on the planning of electric
utilities, so that the insights from this chapter are potentially
important.
This chapter draws upon a very sparse literature base, but
there is seme good discussion particularly on utility operations
and planning. As in Chapter 15, the policy challenge is to get
direct participation by the utilities themselves in research
activities. A start has been made in the Great Lakes region with
Ontario Hydro and the New YorJc Power Authority (see proceedings.
First U.I.-Canada symposium on Impacts of climate change on the
Great Lakes Basin, in press}, the Tennessee valley Authority (TVA),
and the research underway at the Electric power Research Institute
(EPRI).
1?
-------
5• 10 Review of Chapter 17 - Variability
Tie chapter begins with a summary stating that the two models
chosen for the study (the NCAR spectral model, apparently in three
or four variants? and the GIBS grid-cell model) performed poorly
in replicating observed variability in four study regions of the
united states/ hence no change in variability with a climate change
could be reasonably assumed.
Discussion of the National Center for Atmospheric Research
(NCAR) model describes several versions used/ though it is not
clear which was used for which study/ nor why. Since the MC&R
model is spectral, it ought to have been relatively easy to adjust
the truncation to generate averages more closely matching the
spatial scale of the GISS model runs. Instead, "grid cell"
averages for smaller areas are produced, making comparisons between
model results difficult. This is countered, howeverf by the NCAR
study's choice of more closely-spaced ground stations to fit their
small grid spacing; these stations appear more climatically
consistent than those for the GISS study.
Model comparisons with current observations appear to show
both models did better in simulating winter than summer
observations. No quantitative data are presented on variability
calculation for doubled CO2 climate.
When intercoaparing model results, it is important to find
more objective tests than accuracy of matching current data. There
is an important distinction to be made between tuning, calibration,
and predictive capability. If a model does a better job in one
grid cell, is it the one to use? Model validation is clearly a key
ingredient. It must contain elements of data acquisition, as well
as strategies to use the data to tune and validate • the models.
Verification will be especially difficult for higher order effects
such as variability, or, worse yet, for estimating the frequency
and magnitude of rare events like hurricanes.
Climate extremes - winds, rainfall, hurricanes, floods,
droughts - are not defined in a consistent manner. Extreme
temperatures are discussed briefly, with the focus on public health
and agriculture. The public health discussion is also brief, with
no information on mortality norms vs. increases, and how those vary
with length vs. severity of temperature extremes. The agriculture
discussion is slightly longer, but is limited to individual crop
experiments or qualitative summaries. Climate variability
modelling results are discussed in great detail, yet no information
is provided on how variability is actually calculated.
This chapter makes a good attempt at discussing some of the
problems of using climate statistics being generated by current
GCM's. The basic finding that no change in variability is a
reasonable assumption is not surprising. This is because of the
18
-------
resolution of current models - 500m2 or 4 by 8 degree latitudinal
grid squares are simply too large to describe accurately the
weather within. Many of the extreme features concerning severe
storms cannot be accurately be reproduced at these scales. Ik major
improvement in resolution is needed, which raises the question of
the computer power necessary to do the job. % second point
concerns the observational 'data being used to compare with the GCM
results. it can be argued that the actual data are not
representative of the area of concern, which leads one to ask which
is correct; discussion of interstation differences in variability
would be a useful addition to the chapter. There is no question
that validating the results being generated by the GCMa should be
a major research priority* However, we are not sure that the
technology exists at the present time to do such validation
adequately.
This chapter discusses the potential implications of changes
in variability, clearly points out their importance, and indicates
that forecasts of changes in variability will be very difficult to
confirm. While the chapter describes the inter comparisons among
models, the models now available have little relevance for
assessment of changes in variability as causes of impacts from
•limate change. However, variability is a key issue that should
stand out in the report; placing the discussion of variability at
the end of the report downplays its importance. We suggest moving
the discussion of variability closer to the front of the report,
perhaps by incorporating it into Chapter 3, Methodology.
6.0 REVIEW OF THE REGIQMAL
6.1 Review of chapter ........... 4 - California
California is the most complex of the ease studies/ because
of the range of issues involved for this heterogeneous state. While
the case study has many commendable aspects, there are also many
aspects in need of clarification and improvement.
California's ' current climate is highly variable, both
spatially and temporally, suggesting a large influence of
geographical features such as the Pacific Ocean and California's
mountain ranges on its climate. These geographical influences are
not included in GCM models with a grid scale resolution that is
about the same size as the state. Instead, a single point estimate
is used to describe a heterogenous climate from the coast through
Central Valley to the Sierras.
The GCM. results indicating smaller snowpacJcs and faster
snowmelt imply a potential for loss of water resources. Since the
mountain rivers are heavily managed in California through an
extensive networks of dams and irrigation channels, the logic
supporting the authors* conclusions is not clear. Controlled
19
-------
releases from California's dams. has greatly reduced the effects of
mountain floodwaters on lowland cities and agriculture. HOW
adequate is California's water system under an altered climate for
managing irrigation, carriage water/ and flood control? This
question deserves high priority in the future planning of
California's water system. . This case study raises the question
without exploring it in depth.
other examples of the need to consider management interactions
concern the projections about wetlands in San Francisco Bay and
ecosystems in sub-alpine lakes. It is not clear that the analysis
accounts for the facts that the Bay is highly managed as a wetland
system, and that algae production would not be managed in lakes
that are heavily stocked seasonally with fish.
The limitations of the agricultural study methodologies for
California are explicitly stated. Taking into account the
uncertainties, the results of the agricultural studies and their
implications are reasonable as presented. The chapter
appropriately states that it is very uncertain how agricultural
effects would be felt in California* s economic and policy
environment* Of the four case studies, California is the only one
that is not directly comparable to the others. Additionally/ the
study by Dudek does not link well with the national study by Adams*
However, this in no way detracts from the overall report i rather,
it is further evidence to show the difference in agriculture
setting and crops between regions.
Many other aspects of the California case study differ from
the broader analysis and discussion in the national study chapters.
The air pollution analysis is somewhat simplistic* It does not
appear to account for meteorological variability in the national
standard or for increase in mixing height ventilation with
temperature. The support for the electrical demand estimates
suffers from the heterogenieity and variability of California
climates. The terrestrial vegetation study used an analogy that
is different from the <3CM scenarios, so it is difficult to compare
its results with the other regional studies.
The extent of uncertainty in this chapter should not be
underplayed, especially regarding the "definite11 nature of some of
the conclusions. The section on policy implications indicates
clearly the kinds of concerns that planning bodies will have to
deal with, starting in the very near future. If the Effects Report
accomplishes nothing more than beginning the planning process, the
will have accomplished an important goal*
€.2 Eeview of chapter S - Great takes
This chapter discusses impacts on lake levels and temperature,
water quality, fisheries, forestry, agriculture, shoreline
20
-------
infrastructure, energy demand, and United states shipping and
recreation. There are some articles omitted from the literature
review at the beginning of the chapter, which is unfortunate since
the new research effort complements the existing literature on many
issues (e.g. lake levels, shipping, etc.}, NO twiths tending this
omission, the discussion of effects, potential response, and
conflicts is very good. Potential water-use and land-use conflicts
are described, including possible expansion of agriculture into
forest lands t shift in forest species with subsequent impacts on
wood industries, and water management responses to declining lake
levels. The "Findings" and "Climate-Sensitive Natural
Resources * * * " sections occupying the first twelve pages are quite
authoritatively written, and the studies undertaken seem to have
been veil chosen. In general, the material presented contains good
balance between the "advantages" and "disadvantages" of climate
change,
The sections related to agriculture are well done. The
methodology, assumptions and limitations are clearly stated, and
the results and implications are reasonable. The references to
complementary work being done in Canada are useful and informative
- a valuable addition to the work being undertaken in this study.
The bottom line is that it is not clear whether crop yields will
increase or decrease in this region. It really depends on direct
CQ2 effects OH crop growth and how hot and dry the summers get.
The results suggest that there will be a shift in agricultural
boundaries northward. The major question is whether the land
resource base in this region, particularly, the more northerly
is capable of supporting this shift,
6.3 Review... p.f. Chapter_6 - southeast
This is a reasonably well-written discussion, with good
integration of topics. The impacts, which include technical,
economic and legal factors which will influence future responses
to climate change, have been described carefully. Of particular
interest are the legal constraints on water management responses,
the potential accelerated abandonment of agriculture should CO2
enrichment be realized (as in Chapter 4, there needs to be more
discussion about uncertainties related to direct effects of co2) ,
and the possibility that grassland would dominate the future
landscape.
The agriculture portion of this chapter is well written; the
methodology limitations are clearly defined, and the results and
implications of the work presented are generally reasonable*
However, the southeast regional assessment did not faithfully
reflect the conclusions of the national studies* Most notably,
the regional assessments gave much' more credence than did the
agriculture chapter to the possibility of very large mitigation of
adverse effects from climate change on crop production by increased
21
-------
productivity associated with co2 enrichment. The agriculture
chapter correctly highlighted the lack of an extensive data base
on this issue, especially at a level higher than simple laboratory
studies en photosynthesis and water-use efficiency as a function
of co2 enrichment. There are many reasons vhy the physiological-
level responses would not be realized in the real world, such as
interactions of C02 enrichment with elevated temperature, increased
productivity of competing plants, limitations by nutrients and
water (which, after all, are the limiting factors for terrestrial
systems including agriculture, not carbon availability), and so on.
These limitations are given insufficient attention in the regional
case study chapter, and, indeed, scenarios of major offsetting of
temperature effects or even increased crop yields are presented as
if the CO2 enrichment is as well-known as crop yield as a function
of temperature and moisture. The difficulty is that how the CO2
enrichment issue is treated determines the magnitude and even
direction of effects, and subsequent economic and land-use analyses
therefore can be quite misleading.
Potential impacts on forest systems in the southeast with
warning are potentially quite extraordinary. instead of forest
change, the potential exists for forest loss, with regard to the
value of Southeast forest resources, and the .tendency for forest
industry to neve toward intensive plantation culture (independent
of climate change), the prospect of irrigated forest stands is
real,
one drawback noted with this chapter is that the level of the
discussion is often inconsistent, with excessive detail on a
limited number of issues (e.g., water management issues on Lake
Lanier and the Tennessee Valley Authority system) to the exclusion
of more broadly applicable synthesis statements about the southeast
as a region. Also, there seemed to be too much attention given to
sea-level rise, without an appropriate balance given to other
potentially serious problems for the region. If the intent of the
chapter is to identify the vulnerabilities of environmental and
human systems in the southeast to climate change, it did not
adequately accomplish that objective, in addition, in the summary
of findings there are S major conclusions related to agriculture
including the possibility of major yield and acreage declines.
There is no mention of the implications of these for policy and
the economy. Finally, statements in a number of places not to take
the results seriously detract considerably from the implications
sections. The caveats should be written more carefully and
consistently.
€.4 Review of Chapter 7 - Great Plains
The discussion in the Great Plains regional case study focuses
primarily on agriculture, and secondarily on water supply and
tjuality, water resources management and energy demand. However,
22
-------
tills chapter needs to' be made somewhat more substantive. The
existence of a separata chapter on agriculture should not weaken
this chapter to the point whore it can not stand alone. There is
a lack: of differentiation between the northern (particularly
neglected), Central, and Southern Plains and between the opposing
crop yield influences of co2 enrichment and heat/moisture stress.
^
Tie fact that the basis for the hypothesized growing season
moisture stress is really only limited to the GFDL model (which
has hydrological peculiarities) is not adequately stressed. A
further key issue net fully addressed is the extent to which
irrigation can provide (on economic grounds) a buffer against the
suggested climate change (reduce moisture stress more than heat
stress). The 'choice of dryland agriculture vs. irrigation will be
a difficult one, given potentially more severe water supply
problems in a future warmer climate and the uncertainties of
results of CO? enrichment scenarios. The models used, assumptions
and limitations concerning the agricultural studies are clearly
stated* The results and implications stemming from the model
studies are reasonable. 'The challenge may be to find a land and
water resource management scheme that can adapt to a more arid
regime without causing severe economic problems to the region's
population*
The fact that the area is often "marginal" agriculturally
means that climate-induced interannual variability can be high, as
is indicated. But such variability is not as devastating in a
national production sense as it would be for "core" agricultural
states lifce Illinois and Iowa* This aspect needs further
discussion*
The portion of the report labeled as dealing "with, energy
should be relabeled as dealing with electricity, and the reasons
for increasing electricity demand should be stated in the Findings
section. Presumably heating demand for natural gas and oil would
be reduced with milder winters. Zn addition, the report appeared
to have somewhat inconsistent statements regarding water quality
impacts. The Findings section indicated possible benefits to
groundwater contamination due to less leaching. Overall, the
chapter appears to rely on fate and transport results to determine
groundwater impacts when the impacts will depend on total acres
under production, application rates, soil type under cultivation,
and changes in irrigated versus dryland acres*
23
------- |