Note:  Each comment is followed first by the identify of the commenter, then by the response to each comment.  See also:

• List of Those Who Submitted Comments

• Notes on Abbreviations Used

Overview: All of the overview is in the context of societal impacts. It overlooks natural resource issues. These need equally represented in this report.

Response: For the report as a whole, this has been corrected by adding a subsection on interactions of climate change with land cover. In addition, appropriate text is now included in the overview.

Page 1 of this overview provides a very useful perspective on the wide range of climates in the U.S. as well as the role of different elements of US society (from building standards to medical systems) that contribute to the dynamic adaptation that occurred during the 20^th century prior to concern about global climate change. This material is very useful and relevant.

Response: To more effectively summarize the chapter, this material has now been moved to a new Introduction section.

Page 1, line 23. There is no statistically significant increase in drought frequency or areal magnitude as measured by the Palmer Index in the last 100 years. There is an increase in the area of the country that is wet as measured by the same index. Change the text to reflect the truth: There is an increase in wet conditions but no increase in dry conditions.

Response: The sentence referred to does not indicate that there was an increase in drought; it only indicates that there has been an increase in intense rainfall events.

Page 1, lines 23-24. The study referred to here, by Karl, describes increases in rain events that are not likely to have produced significant flooding. The increase in high-intensity rainfall works out to less than one inch per year, averaged nationally. This calculation can be readily deduced from his 1995 Nature paper. If you're going to assert a change, at least show how little it has been.

95th percentile 24-hour precipitation in the U.S. is approximately 1.3 inches (based upon a preliminary analysis of U.S. HCN data from 1900 through 1987). That is not intense. Even using the two-inch threshold, 11% of the 34 inches of average annual national rainfall comes from that category, or 3.74 inches. As Karl et al. showed in Nature in 1995, the increase in this class was from 9% to 11%. That works out to 2% of 34 inches, or 0.68 inches per year.

Response: The sentence as written does not indicate that these more intense rainfall events cause flooding (although clearly some do as the reviewer has cited only the lower cutoff of such amounts). With respect to estimating amounts of rain, averaging across the US has the effect of mixing data from quite dry areas with quite wet areas. It also has the effect of not properly including consideration of the very high, but very rare, rainfall events. As proposed in this comment, it is simply not appropriate to average and then present that figure as a point of reference when events such as those that have happened in Houston, New Orleans, and elsewhere have had very large numbers.

Page 1, line 25. Parmesan's butterfly study shows a large decline in frequency in a grid cell that is actually cooling (!), with major expansions in the northern part of the range, which is warming. In Europe, she finds a large expansion of range, implying increased biodiversity. She never checked the weather data for Southern California, which is available from the IPCC nor did she comment on the range expansion, nor is the writer of this paragraph in the USCAR familiar with these truths.

Response: Checking with the National Climatic Data Center, which keeps the records of changes in temperature, they report that the southern California grid cell does indeed show a small annual cooling for the 1978-98 period (we would suggest that the amount of cooling matters), with summer and fall showing cooling and winter and spring showing warming (and it matters during which seasons it is occurring -- and so do changes in other variables and other stresses). In any case, everywhere else along the West coast is warming.

With respect to the expected and observed response of the butterflies, one has to be very careful here to consider what the actual temperatures are by season, changes in precipitation, etc. What is seen primarily is a northward shift of butterflies in areas near their cold margin (so northern California and up the West coast) where observations indicate warming, which would seem to be the major point of the butterfly article. At the southern edge, even if there is annual cooling (and recalling the seasonal cycle), it is not clear why there should be an expectation that this would be contradictory to some decline in butterflies occurring.

With respect to the European comment, one cannot just simply relate biodiversity and temperature. First, no overall increase in species is likely to occur over short time periods -- new species emerge over long times -- so, there may be more varieties at some point, but this does not mean an overall increase in biodiversity; in fact, because climate change causes loss of some species, overall biodiversity is decreased, even were some points, or even all points, to have more varieties present. In addition, what matters is not just how one species moves, but the full interactions of the ecosystem, so plants and wildlife symbiotically, and how they respond -- there must be the right types of food at the right time and in the right amounts, etc. As the rate of climate change increases, ensuring continuing adjustment of such linkages would seem to become more and more problematic as different species respond differently to the various stresses and changes.

In any case, the IPCC reports on apparent shifts of many species, and, even though there are other influences on the ranges of species (like changes in land cover, etc.), it finds the vast majority consistent with expectations of how the species would respond to the observed changes in climate.

Page 2, lines 5-7: �However, recent trends � -- What studies are being referred to here? In fact �The projected rate of warming is much larger than the observed changes during the 20^th century � -- page 69, IPCC, Third Assessment Report Volume I, therefore recent trends are not a good indication of warming in the 21^st century. In terms of projections, the temperature projections are based on The Emissions Scenarios of the Special Report on Emissions Scenarios (SRES), which consist of 6 scenario groups, and 35 total scenarios. �All should be considered equally sound. -- There is therefore no �best estimate -- and the lower range is definitely not highlighted as more likely.

Response: While the IPCC considered all scenarios as equally sound, this does not mean that they are equally likely. Studies, for example, by Schneider in Nature and Wigley and Raper in Science, for example, suggest that the warming is likely to be in the lower half of the IPCC range. Because these are only individual and not IPCC assessments, the word �some -- has been inserted to modify �probabilistic studies. -- A reference was also added.

Page 2, line 7: Discussion of reductions in GHGs over the course of the 21^st century without reference to the timeframe of atmospheric concentration stabilization is misleading. You must including discussion of the amount of time required to stabilize concentrations.

Response: Phrasing has been adjusted to indicate this.

Page 2, Lines 7-9. This sentence makes a large assumption that is not based on model evidence, namely, that �future changes in mean and extreme conditions will be similar to past variations -- . On the contrary the models project much greater changes in both mean and extreme conditions than that experienced during the 20^th century.

Response: The phrasing has been corrected to clarify what was intended. The following sentence then indicates what would be expected if variability increases.

Page 2, line 17

For readability, there should be a paragraph break with the beginning of the sentence in this line.

Response: Change made.

Page 2, line 18

This line should refer to �Articles 4.1(b) and (e) -- , not �sections 4.1(b) and (e) -- of the UN Framework Convention on Climate Change.

Response: Change made:

Page 2, Line 18: Delete �more likely --

Response: Change was not made. See general comment 11.

Page 2, Footnote 1: Delete

Response: This change was not made. The issues surrounding this matter are discussed in the response to general comment 11.

Page 2, Footnote 1

With the reduced emphasis on specific regional climate change impact possibilities, this footnote probably should be deleted. If retained, it should be shortened, made consistent with the NRC material, and relocated to the text in the middle of page 3 (see following [API] comment [so, second comment down]).

Response: This lexicon was developed by the NAST to use in the presentation of potential impacts of climate change and so applies more generally than to just the section on weather and climate (which is where, it appears, it is suggested that this text be moved). Thus, it has not been moved. Also, the NRC report dealt mostly with the issue of potential climate change rather than with impacts. Also, the NRC's failure to address the extensive efforts carried out by the IPCC (and mirrored by the NAST) to develop a lexicon for effectively communicating scientific findings to a general audience makes the suggested review comment moot.

Page 3, lines 15-25: This doesn't really say anything pertinent. It is a broad overview designed to minimize our interpretation of the impacts of climate change. It needs more substance.

Response: For this document, we believe it important to provide a sense of context before describing the potential impacts of climate change. Therefore, this paragraph has been kept. More detailed information of the type recommended by the reviewer is available in the various assessments.

Page 3, line 27 through Page 4, line 28

These lines should be extensively re-written to highlight the following main points:

• The NRC conclusion that �[the] current analyses are unable to predict with confidence the timing, magnitude, or regional distribution of climate change�. -- (from Chapter 1, page 3)
• Develop new text to describe existing Figure 6.1 and using the divergent modeling results to illustrate the NRC's concern.
• Develop new text to describe existing Figure 6.2b and using the divergent modeling results to further illustrate the NRC's concern.
• Keep existing text discussing events of the 20^th century.

Response: As indicated in the response to the general comments, the climatic changes being described are NOT predictions of actual changes, but are projections of plausible changes, which is all that is currently possible with available climate models. Thus, we believe the main parts of the text are consistent with the findings of the NRC as cited above. To clarify these points here, the introductory sentences to the cited paragraph have been changed, as has the caption to Figure 6.1. With regard to Figure 6.2(b), while we agree that the results of this figure indicate that a reliable prediction cannot be made, the point of the figure is to show that a range of possible future outcomes was considered, which is particularly important to do given the uncertainties and need to consider different scenario possibilities.

Page 3, Line 29: Delete �heavy -- and �are likely to be -- . Add �in excess of 2 inches per day --

Response: The sentence has been reworded to make clearer that the notion of �heavy -- is intended to be locally determined rather than being based on some absolute amount (e.g., 2 inches per day). Using an absolute standard would not properly recognize the present range of values of precipitation that occur across the country. The word �likely -- is kept because this type of response is already evident in the observed record, it is projected by many models, and it is consistent with our theoretical understanding of how the energetics of the atmosphere is changing.

Page 3, line 36: What is the word �what -- doing in this sentence?

Response: It should not have been there and has been deleted.

Page 4, line 34, to Page 5, line 3: The description of the El Ni�o cycle fails to mention that while modeling of El Ni�o with climate change is complex and still evolving, the IPCC TAR I (page 73) does state that �� global warming is likely to lead to greater extremes of drying and heavy rainfall and increase the risk of droughts and floods that occur with El Ni�o events in many regions. -- In addition, many models point to a mean El Ni�o-like response in the tropical Pacific, which would make an increase in El Ni�o-like conditions over the 21^st century likely.

Response: Text has been added to make these points.

Page 4, lines 1 and 18: What models are being referred to in these sections? We need citations to evaluate their accuracy. This whole section actually needs many citations to support the claims made.

Response: In that this is an overview chapter reporting on the findings of leading assessments, particularly the IPCC and the USNA assessments, the chapter is not designed to provide all of the information of importance to those seeking detailed references. A note has been added to the front of the chapter making clearer that the interested reader should go to the cited assessments for further information.

Page 4, lines 18-21. The models in figure 6.2b are worse than random numbers (see above). It is scientific malpractice to use them. I choose my words carefully here. If a physician prescribed medication that demonstrably did not work, he would lose his license. If this continues in the report, critics will probably write nasty op-eds that will discredit the entire process.

Response: We disagree with this characterization, as is fully explained in the response to general comments 16 and 17 above.

Page 4, line 30 through page 5 line 17.

This provides useful information regarding shorter-term climate change and probably should be kept.

Response: No response needed.

Pages 5-29. These are based heavily on the US National Assessment. APPENDIX 1 contains comments on the National Assessment. These were by-and-large unanswered when they were submitted; consequently, they apply as well to the Climate Action Report.

Response: Dr. Michaels is simply mistaken. All of the comments submitted by all reviewers of the public comment version of the USNA were specifically addressed. Responses were generally by making textual changes, if appropriate. Alternatively, where the change was not agreed to, responses were provided as to why the comment did not merit a change; all the answers are on file at the National Science Foundation.

Page 5, lines 38-45

An important question that needs to be asked regarding the content of the Third U.S. Climate Action Report is, what level of reliance should be placed on the regional impact findings of the Clinton Administration's National Assessment in light of the IPCC's and National Research Council's conclusions regarding our current inability to do meaningful regional climate modeling? If the IPCC's and NRC's conclusions are to be taken seriously, then highlighting the regional climate results from the National Assessment would present inconsistent and unreliable research to readers and the UNFCCC.

The existence of the National Assessment effort is duly noted in Chapter 9. Considering the goal of condensing this Chapter without presenting unnecessary or conflicting material, lines 38-45 and Tables 6.1 and 6.2 should be deleted.

Response: Just because climate models cannot reliably �predict -- changes in climate on a regional level does not mean that there will be no changes, much less that we do not have a rough sense of what these changes might be. The model results (along with other approaches) were used to derive estimates of plausible types of changes in climate across the US, and these are useful in identifying the types of changes that might occur and to consider how best to build resilience to the types of possible outcomes. To shorten the chapter, Table 6.1 was dropped.

Pages 6-10 -- Climate Change Interactions with Agriculture

In general, the agriculture provides important and useful information. However, page 9, lines 15-21 are vague and the emphasis on �all else being equal -- circumstances runs counter to the frequent references to adaptation in this chapter. The �all else being equal -- statement may be a traditional analytical reference point, but as a practical matter the agricultural sector has proven itself to be highly adaptive, so the �all else being equal -- perspective simply is not useful. Lines 6-10 should be deleted.

Response: The phrase �all else being equal -- has been changed to clarify the intended meaning; the change indicates �in the absence of adaptive measures. -- We were unable to determine which �lines 6-10 -- were suggested for deletion.

Page 6, line 39-40. ��the rising concentration of carbon dioxide (CO2) and continuing climate change are projected, on average, to contribute to the long, upward trend in crop yields. -- While increased temperature and CO2 concentration could contribute to increased crop yields, the other factors listed in the paragraph, especially increased climate variability (more droughts and floods), water quantity and quality issues, and increased need for fertilizers could lower crop yields. The paragraph is written in a misleading fashion.

Response: A qualifying phrase has been added to the sentence.

Page 6, line 40: How long is the �long, upward trend -- ? 50 years, 100 years, 1000 years.

Response: The text has been clarified to indicate that it covers at least the last half of the 20^th century.

Page 7, line 2: Discussion of �adequate supplies of nutrients -- should include a discussion of the widespread issues of nitrogen pollution. There is a wealth of research on this topic out there. Some of it should be integrated here. It is a problem increasing in magnitude and is only predicted to get worse and no actions are being taken to correct it. It is very likely that there will be detrimental synergistic interactions between climate change based stresses and nitrogen based stresses on systems in the United States (possibly the dead zone in the Gulf of Mexico).

Response: A phrase has been added to introduce this point. However, more complete discussion of this point seems too detailed for inclusion in this chapter.

Page 7, line 16: Listing wheat and rice as crops with uncertain impacts and leaving it at that is a bit disconcerting. These are big crops for feeding the world. Not knowing their future makes one less confident that this won't be a problem for agriculture.

Response: A phrase has been added referring the reader to the more detailed underlying studies. It should be noted that this comment refers to changes in yields (and this in the absence of the upward trend as a result of technological improvements) whereas what matters to the people of the world is production, and if yields go down, then the area planted can be increased so as to meet needed production. In addition, given the global marketplace for foods, what really matters is what is happening in the set of growing regions, and we agree that this should be subject of more careful study as the uncertainties are troubling; however, such work remains to be done.

Page 7, line 24-25 �The crop models that were used in these studies assume that the CO₂ fertilization effect will be strongly beneficial � -- While the CO₂ fertilization effect has been shown for certain species under controlled conditions, many studies have shown that the effect may not be long-lasting, that species adapt to higher CO₂ concentrations after as little as a few years, saturate in terms of productivity (do not increase beyond a certain point), and require large increases in fertilizers to realize increased CO₂ benefits. Therefore if increased crop model yields are dependent on the CO₂ fertilization effect, their projections are likely to be in error.

Response: We believe the reviewer is referring to the situation with trees rather than crops. Indeed, for trees, it is being found that the growth spurt due to increased CO₂ may well last only a number of years. However, for crops, indications are that CO₂ fertilization will indeed enhance growth.

Page 7, line 34-35. �� unless there is inadequate or poorly distributed precipitation � -- This is precisely what is projected by the climate models, as stated in this report as well as the IPCC and National Assessment, that periods of drought and heavy precipitation events will increase. Therefore economic studies that predict positive benefits to the agricultural sector are based on studies that do not include likely climate consequences, namely increased extreme events and weather variability.

Response: It was just to investigate such issues (and many more relating to timing, etc.) that the agricultural production studies done for the USNA utilized the more detailed projections of changes in climate conditions rather than simply assuming a few degree warming, etc. With readily available adaptive responses, the various studies indicated that the types of changes projected would not, on average, negatively affect US agricultural production, even though some regions might well experience negative impacts (see the Agriculture sector report for details).

Page 8, lines 10-22: This section fails to mention the detrimental impacts of water use (for agriculture and municipalities) on the ecosystems from which it is extracted. For example the Owens Valley of California, and other Western water projects, some of which have required judicial action to protect endangered species water rights.

Response: In that the overall projection is that US agricultural production will, on average, increase and will require less irrigation water, it was not felt that going into regional issues about impacts occurring at present was appropriate.

Page 8, line 19-22: No and reduced tillage farming methods have been promoted since the late 70s and early 80s in the Midwest to reduce erosion and water use. I find it highly unlikely (especially since there is a complete failure to present any compelling citations) that future efforts will be more successful, with additional buy-in.

Response: In that no or reduced tillage helps to enhance carbon storage, which will improve soil moisture as well as become a tradable asset, and that it also reduces the need for diesel fuels for the tractor, there seem to be incentives that should further encourage its use.

Page 8, lines 24-34: This section is in need of myriad citations to support the many claims. Especially lines 29-31 and lines 31-33. The final lines (33-34) present a solution with no indication of whether or not such research is underway. This definitely needs a citation.

Response: A clarifying comment at the start of the chapter, and a change at the start of this paragraph should help to make it clear that more details (and citations) are available in the USNA reports.

Page 9, lines 4-10: This report is happy to make random predictions in all the other topic areas. Why not make some predictions about what might be the outcome of increasing pesticide use. It will likely have ill effects. To the best of my knowledge there is no existing research that says that increased pesticide loads in nature ecosystems improves their success.

Response: This chapter sticks quite closely to the USNA analysis, and the experts involved in that process were unwilling to come to such conclusions, given various types of responses to pests that may be possible. We do not feel that drawing new conclusions is appropriate in this chapter.

Page 9, line 21: �lower precipitation may reduce such impacts. -- The converse can not necessarily be assumed to be true. Drying conditions (wind erosion and episodic rain moving dusty soils) can also cause erosion. Additionally drying can limit dilution making contaminant point sources more concentrated.

Response: The phrasing has been changed to be less definitive.

Page 9, line 23-33. As in comment above (re Page 4 and 5), models project that El Ni�o-like conditions are likely to increase, exacerbating the climate variability projected here. This should be mentioned in the context of this discussion.

Response: A sentence has been added to make this point.

Page 9, lines 30-33: The assumption that we can prepare for weather anomalies if we have sufficient prediction time fails to note that we can not even do this adequately for established weather patterns. I don't think that the predictive meteorological science exists yet for what is being asked of it here. A citation otherwise would be useful in making your point.

Response: Studies done examining the value of seasonal predictions for the southeastern US, Brazil, and elsewhere indicate that predictions of seasonal anomalies can be highly useful. Although a citation is not provided, again, the text is being changed to point the reader to the underlying assessment studies.

Page 9, line 41-43: A citation would be swell.

Response: Again, this is intended as an overview paper. Such information is available in the various assessment reports.

Pages 10-14, Climate Change Interactions with Forests

The section begins (page 10) with useful introductory material including the many ways human activities may impact forests.

Response: No response is needed.

Page 10, lines 40-42: Landscape use of trees is not generally considered range expansion. Two major reasons: 1) often this does not include reproductively viable populations (i.e. sex selection in ginkos, lack of surrounding land for expansion of cluster) and 2) landscaping frequently uses exotic species not indigenous to even the continent on which they are planted. There are also additional issues of hybrids and genetic selection.

Response: Wording has been modified to indicate that this has �extended the presence of some species. --

Page 11, lines 6-8: These lines cover results from a single model and describe �changes that climate change could have on forests�. -- Does this �could have -- result really have a strong enough basis for inclusion in a report to the UNFCCC? If not, the text should be deleted. There are numerous other examples of specific regional �results -- being provided in Forest section. Again, if the NRC and IPCC conclusions about the reliability of regional modeling is to be taken seriously, these regional results don't belong in an official US report to the UNFCCC.

Response: In that the presentation is not about predictions of expected change but an example of a plausible type of change, providing this as an indication of the relative magnitude of the type of change seems useful. The wording has been clarified to make it clearer that this is a hypothetical indication of potential changes.

Page 11, line 14: What are the �some warmer scenarios -- that are referred to in the text? Citations, parameters, explanations�

Response: Wording has been clarified. Again, reference should be made to the underlying reports for further details.

Page 11, lines 10-18: What about land use loss? Forest (or other wildlands) conversion to development (buildings, roads, etc�) or poor harvest practice loss of forests and �carbon. --

Response: The example of �development -- has been added.

Page 11, lines 21-22, 23-26, 27-28: All of these points need citations to support them.

Response: A referral to the underlying studies has been added.

Page 11, lines 32-33: Alternatively some species are very susceptible to fire, or require periodic fire regimes (of a certain intensity) to reproduce successfully. Large-scale, intense and frequent fires do no good for these types of vegetation.

Response: An additional phrase has been added in recognition of this point.

Page 11, line 36: �These changes in disturbance regimes are a natural part of all ecosystems. -- This statement is pointless. Every parameter discussed in this entire chapter falls under this clause (precipitation, atmospheric gas concentrations, etc�). Making this statement simply tries to lessen the potential importance of the impacts.

Response: The statement is included to try to provide overall context for the following sentences which create limits for it. Thus, it is felt that it is appropriate to include when read in overall context.

Page 12, lines 4-5: According to this text, �what is clear is that, as the climate changes, alterations in these disturbances and in their effects on forests are possible. -- As defined in the existing footnote 1 on page 2, �possible -- in this report only means that the odds are about 50/50. If the science on this issue is refined only to the point of a coin-toss, does it merit inclusion in an official US report to the UNFCCC? In general, this section needs to be shortened and �coin-toss -- material deleted.

Response: Rather than enumerate a number of specific examples and in view of the potential that various adaptation measures may alleviate some of the stresses, the word �possible -- was used to summarize the potential outcomes in the NAST Overview report. The Forest sector brochure, which is based on the published, peer-reviewed articles done for the Forest sector assessment, is actually more definitive, making the point that �an extensive literature suggests new disturbance regimes under climate change are likely to result in significant perturbations to US forests, with lasting ecological and socioeconomic impacts. -- Because this chapter is based primarily on the National Assessment Overview report, with its wide consideration of many types of impacts, we chose to stick to the choice made there rather than to use the level of confidence in the Forest sector assessment. We retained mention of this issue because it is judged to be one of the most important for the forest sector.

Page 12, line 7: The title of this section should be, �Effects of Climate Change on Forest Biodiversity --

Response: Change made.

Page 12, lines 7-24: Throughout this document but especially here it should be recognized that it is not just species that need to be addressed but populations. The world of conservation biology and ecology now focuses on the importance of populations and the unique genetic composition each encompasses. Protection and adaptation to climate change impacts must focus on populations as the crucial unit of biodiversity.

Response: Revisions made to make this point.

Page 12, lines 7-10: What about other abiotic factors? Weather, contaminants, nutrients, etc...

Response: Clarifying sentence was added.

Page 12, line 14: Please not that �time and space scales -- are correctly referred to as �temporal and spatial scales. --

Response: Change made.

Page 12, lines 15-16: Add abiotic habitat to the list of factors that determine the distribution of plants and animals.

Response: Text changed to address this point.

Page 12, line 16: Again �ecological models -- are mentioned with no indication of which ones.

Response: Phrase added to point reader to USNA.

Page 12, lines 21-24: It should also be noted that populations isolated on mountains will be lost as they can only shift up in altitude, not latitude, due to their isolation which is likened to an island. If you had a section on island populations you could also discussion populations of biota isolated on true islands, as this is another important topic.

Response: The new section on interactions with land cover makes this point.

Page 12, line 23. The economic impact is decline and eventual loss of syrup production in New York and New England. This should be stated explicitly. (see New England Regional Assessment)

Response: Phrase added.

Page 12, line 40: Rather than �weed -- species the terms used are generally �weedy -- or �cosmopolitan --

Response: Change made.

Page 13, lines 1-2: A citation of these assertions would be helpful.

Response: It seems sufficiently obvious that an increase in forest growth per unit area will lead to a smaller area needing to be disturbed to meet the same demand.

Page 13, line 15: �Analysis indicates� -- requires that the reader know what kind of analysis was done and who did it.

Response: A phrase was added to indicate path to references.

Page 13, line 21: An alternative approach might be to increase harvesting to make up lost revenues (due to decreased prices); this would adversely impact forest habitat.

Response: Given the low margins and existing regulations on how harvesting is done, this would seem to be a less likely outcome.

Page 13, lines 24-29: Lots of assertions in need of citations.

Response: Reference made to forest sector assessment, which is based on several published articles.

Page 13, line 32: Here is a mention of the concept of benefits, yet the paragraph goes on to only describe detrimental aspects. Why include the mention of unsupported benefits? If it is to be kept in the text, I suggest the addition of a supporting citation.

Response: The word �benefits -- is meant here to mean �forest-oriented recreation -- (which we hope all agree is beneficial), but to clarify the text and avoid jargon, the longer phrase has been repeated.

Page 13, line 40: �..opportunities for some warm water species� -- What does this mean? Does the extinction or extirpation of one species, or population, is not offset by the expansion of another. While a rose may be a rose, a rose is not a hydrangea. The loss of species and populations is not a net balance equation. Each one is of value and concern. I would like to think that we know a bit more about the nature of ecosystems at this point in time than is taken in the lighthearted view that one fish is just as good as any other fish. Even if you ignore the inherent value of each species and population, you need to look at what niche each fish fills to know if the new fish really is a replacement.

Response: The phrasing has been clarified that what is meant here is the opportunity when fishing to catch warm or cold water species, and does not refer to opportunities for fish to now inhabit additional streams.

Page 13, lines 43-45: Economic activity and economically motivated adaptation strategies will not benefit natural resources, only economically maintained systems (agriculture, development, infrastructure, commercial forestry) not natural systems.

Response: While increased economic activity can indeed lead to greater exploitation of natural resources, experience also indicates that the additional wealth of industrialized societies allows more attention to be paid to environmental concerns. Both aspects are meant here, and so we believe the text does not need to be changed.

Page 14, line 1: ��changes in taste, and general preferences� -- This disregards the idea of stewardship of national natural resources. By leaving them to the marketplace we remove governmental responsibility for all people.

Response: It is intended that the notion of stewardship be excluded here. Although perhaps vaguely presented, the concept of stewardship, along with other philosophical approaches, was intended to be encompassed by this phrasing.

Page 14, lines 4-6: Action is mandated for protected areas regardless of the cause of the threat. Once something is designated as protected there is an obligation to development mechanisms for its protection. Such actions regarding climate change protections and adaptations must be supported in the development and expansion of all protective mechanisms (reserves, parks, sustainable harvest, etc�).

Response: In that change is occurring (and has occurred in the past, although less rapidly), it is simply not possible to preserve all (or even any) protected areas in exactly their present state, whether it be the Everglades that are likely to eventually be inundated by sea level rise or alpine species that are expected to no longer be able to survive where they are as a result of climate change. Judgments will need to be made by resource managers about how to deal with this situation in that simply standing at the guard gate with a gun (or court order) will not allow the preservation of the present (or re-creation of a past) environment. Replanting or relocation of some species in new areas may prevent extinction (or even encourage enhancement) of a species so that, in total, protection is achieved, but climate change is going to necessitate some adjustments and require use of the judgment of resource managers to optimize the situation.

Page 14, line 36: It is stated, �Some 53% of the total US population live on the 17% of land in counties bordering the coast. -- This sentence is incorrect as written. These percentages are based on information from the Department of Commerce (National Oceanic and Atmospheric Administration [NOAA], and Bureau of the Census). However, these agencies consider a county to be a "coastal county" not if they border the coast, but if: 1) at least 15% of its total land area is located within the nation's coastal watershed; or, 2) a portion of its land accounts for at least 15% of a coastal cataloging unit. By this definition the United States has 673 coastal counties. FEMA has determined that there are less than 300 counties that actually �border -- the coast. FEMA's definition requires that at least some part of the county must (1) be contiguous with the open ocean or Great Lakes coast, or (2) be impacted by wave action.

Note that coastal counties that comprise "17% of land in counties bordering the coast" (i.e., the Dept. of Commerce Definition) include counties such as Sussex County, NJ--a completely landlocked county located completely in the Piedmont and Appalachians, and approximately 35 miles from the nearest coast. Indeed, the Dept. of Commerce considers all counties in NJ except one to be �coastal counties. -- (Note that NJ has about 13 landlocked counties.) All counties in Florida are considered "coastal counties" even though about 29 counties are completely landlocked. Even Appomattox County, VA, is considered by the Dept. of Commerce to be a "coastal county"! It is located about 120 miles from the Chesapeake Bay and about 150 miles from the open ocean coast.

It is highly recommended that this sentence be corrected.

Response: Text was modified.

Page 14-15, lines 44-1: Will this process make land cleaner or water more polluted?

Response: This will depend on how we choose to prepare for and adapt to the changing conditions, and what other changes we choose or do not choose to make to ensure improvement of both the land and the ocean.

Page 15, lines 2-5: This example needs a citation.

Response: A phrase has been added pointing the reader to more detailed information.

Page 15, line 7: What interactions are �these interactions? --

Response: Text has been clarified.

Page 15, line 8: Should read, �Melting of glaciers and ice sheets� -- Ice sheets are included farther down the page, they should be mentioned here too.

Response: Changed as suggested.

Page 15, lines 11-13: citation required

Response: A citation is included at the end of the paragraph.

Page 15, line 17ff: Global warming is linked to (1) alteration of weather patterns, which �could affect the intensity, frequency, and extent of severe storms, -- and (2) rising sea levels and beach erosion. It is pointed out that the Atlantic and Gulf coasts are particularly vulnerable, especially �if there is an increase in the frequency or intensity of storms or hurricanes, because the slope of these areas is so gentle that a small rise in sea level produces a large inland shift of the shoreline. -- A point that appears to be alluded to, but not explicitly stated, is that sea level rise (while causing the �large inland shift of the shoreline -- ; i.e., erosion or inundation), will also cause coastal flood elevations to rise, thereby allowing deeper inland penetration of storms. This is important because even if there were no increase in storm activity as a result of global warming, rising seal levels alone could worsen flooding from current storms that would have been relatively insignificant decades ago. Indeed, it should be noted that Zhang, et al., in a September 16, 1997 EOS article show that �tide gauge records from Atlantic City and Charleston show inter-decadal variation of storminess, but no discernible long-term secular trend in storm activity during the 20^th century. -- The authors note that regardless of this finding, �the effect of sea level rise over the last century has exacerbated flooding from modern storms that would have been relatively inconsequential a century ago for fixed coastal locations. --

Response: Changes were made to the text to indicate that a rise in sea level even in the absence of a change in storminess will cause impacts.

Page 15, lines 21-23: citation required

Response: Citation added.

Page 15, line 36: in addition to �fisheries -- , � other coastal biodiversity -- should also be added to the list of factors to be affected. Perhaps there could even be some discussion of sea turtles losing breeding habitat with sea level rise.

Response: �Coastal ecosystems -- was added as a category.

Page 15, line 45: Filtration and water purification is also seen as a benefit of estuaries.

Response: Additional benefit is now noted.

Page 16, line 1-4: citation required

Response: Referral is now made to the Coastal assessment.

Page 16, line 10: �blooms of algae -- are more commonly referred to as �algal blooms --

Response: Change made.

Page 16, line 11: What are the �stresses -- that will increase on �sea grass, fish, shellfish and other organisms� -- Please be less vague.

Response: Given the many habitats, there are many types of stresses. An enumeration here would be too lengthy and detailed so a reference to the report has been added.

Page 16, lines 12-14: The statement �estuary habitat susceptible to predators and pathogens of shellfish -- needs a citation and greater explanation.

Response: Again, this chapter is not intended to be an authoritative assessment in and of itself. Reference to the Coastal report is considered sufficient reference.

Estuaries section in general: Also to be included in the list of impacts on estuaries should be sea level rise induced salt-water intrusion and shifting of habitats.

Response: Phrases added to make this point.

Page 16, line 23: Here is discussed the idea that wetlands may be able to migrate inland. This overlooks what then happens to the inland habitat that it is moving into. You are seeing the reduction of one problem with the creation of another.

Response: A phrase has been added to make this point.

Page 16, lines 26-28: How will the impacts vary among regions? What is the citation?

Response: There is insufficient space to describe potential regional consequences in detail; a citation has been added.

Page 16, line 35: What is meant by �genetic resources -- ?

Response: The phrase �genetic resources -- seems a sufficiently clear description of the fact that the biodiversity of marine life, like that of terrestrial life, provides a vast array of examples of how nature has developed responses to various stresses, etc., and these may serve as resources for developing medicines, etc.

Page 16, line 36: How many years are the �last few years -- ? Be more precise.

Response: This is regionally dependent and seems sufficiently precise for a general description. Citation is now made explicitly to the Coastal assessment for further information.

Page 16, line 43: Perhaps it could be rewritten as: �In addition to increasing sea surface temperatures, a number of factors are likely to also be contributing to the decline�. --

Response: Change made.

Page 17, line 3: Using the term �increased vulnerability to erosion -- requires more detail. Are you referring to bioerosion?

Response: Rephrased to say to �wave-induced damage. --

Page 17, line 4: �margins of coral reef distribution -- might better be described in terms of range. Also be clear about what limits are of concern (latitude, depth, currents, or any range limits).

Response: �margins -- has been changed to �edges. -- With this change, the sentence seems clearer.

Page 17, line 7: Artificial reef is generally employed to protect and promote fish growth, not coral growth.

Response: Phrasing has been changed to clarify that these means are mainly effective in reducing the impacts of some types of stresses on coral, rather than directly reducing the stress on the coral.

Page 17, Marine fisheries section: Many citations are required.

Response: Again, reference to the underlying Coastal assessment has been added.

Page 17, line 22: �sea lion -- might more accurately be described as by including the actual species name, perhaps you mean the �California sea lion. --

Response: Change made.

Page 17, line 36: Please further describe the �adaptation to climate change --

Response: This does not seem the place to summarize steps being taken to better manage the world's fisheries. The point is only that at least some of these measures are likely to make fisheries less vulnerable to climate change.

Page 17-18, lines 45-2: Point well made. But again, a citation would be nice.

Response: Citation added to the Coastal assessment.

 Page 18, lines 24-27: Again, point well made.

Response: No response necessary.

Page 18, line 31: FEMA recommends inserting: �As part of its mandate and responsibilities to administer the National Flood Insurance Program (NFIP), FEMA prepares Flood Insurance Rate Maps (FIRMs) which identify and delineate areas subject to severe (1% annual chance) floods. FEMA maps coastal flood hazard areas as a separate flood hazard category in recognition of the additional risk associated with wave action. -- in between ��the public. -- , and �FEMA is also� --

Response: Suggested insertion was made.

Page 19, Line 19: Add -- runoff is �sometimes -- observed

Response: The word �generally -- was added given the focus on a limited set of conditions where such a response tends to be likely.

Page 19, lines 21-30: Why isn't the issue of available water supplies linked to agricultural issues as well?

Response: A sentence on the primary uses of water has been added.

Page 19, lines 35-37: Don't forget to add local species that are reliant on water being in those waterways.

Response: Phrase added.

Page 20, line 1-2: Again, point well made.

Response: No response needed.

Page 20, lines 1-2: Additionally reduced water can lead to concentration of contaminants in water bodies and therefore lead to increased toxicity.

Response: Change made.

Page 20, lines 8-12: Citation required.

Response: Reference to Agricultural and Coastal assessments is now included.

Page 20, line 10: See previous comments regarding the need to examine what we already know about the success of promoting no and reduced till agriculture. A citation would, as always, be nice.

Response: Wording modified so as not to imply that this is a new concept.

Page 20, line 17-18. Snowpacks provide a natural reservoir for water storage for the western and northern portions of the US. The site of the storage is in mountainous regions and northern portions of the US. The wording needs to be improved here for clarity.

Response: Wording clarified.

Page 20, line 18: Perhaps this could be better worded as, ��U.S., gradually releasing its water in spring and even summer. -- The inclusion of �presently -- is only necessary if the melting will no longer occur in spring and summer. Rather it seems that the point being made is that there will be less snow.

Response: Wording clarified.

Page 20, line 18: Again, name the models. You show them in the figures, cite them in the text.

Response: In that models generally show this, naming specific models in the text seems inappropriate. Instead, an �e.g. -- has been added to indicate that the figure is only an example of such model results.

Page 20, line 22-25. ��have implications� -- change to �� have many serious and negative implications � --

Response: The adjective �significant -- has been added. How the implications work out depends on what sorts of adjustments can be made, so it would be premature to suggest that all are �negative. --

Page 20, line 25: Add �species -- in addition to �natural habitats. --

Response: Change made.

Page 20, lines 27-29: Point well made but a citation is required.

Response: It should be sufficiently clear by now that the reader should refer to the Water sector assessment for more information.

Page 21, line 17: Should read ��hurricanes may have higher --

Response: While there is no convincing indication of how climate change is likely to affect the number of hurricanes, the physics of hurricanes and available studies with the well-tested US hurricane model indicate that hurricanes that do develop are likely to be stronger because there is more moisture (and hence latent heat energy to drive the hurricanes) in the atmosphere and because the tendency of the GHG enhancement to stabilize the atmosphere will mean that more energy will be needed and is available to drive the hurricanes. Together, these influences seem likely to lead to an increase in average windspeed of the hurricanes. Hence the phrasing has not been changed.

Page 21, line 19: Add after the last sentence -- Historical trends, however, do not show an increase in damages faster than the increase in assets at risk.

Response: The point being made is that increases in windspeed will increase damage, and this is clearly the case (it is basically how the hurricane category scale was set up). It is true, but not relevant here, that there is one study showing that if hurricane damage is scaled by population and inflation, etc., the damages are not going up faster than the assets at risk. Frankly, however, this should be small comfort given the effort to make people aware of potential damages and to build buildings to higher standards, etc.

Page 21, line 28: �Species live in the larger context of ecosystems� -- What does this mean? This is a vague assertion with no real point.

Response: We disagree. The point is that one cannot think about the potential interactions of climate with a particular species except in the context of what is happening to its total environment -- from its predators to prey and from its habitat to its exposure.

Page 21, line 29: �differing environmental needs -- does this mean �unique niches -- ?

Response: One could say the species fill differing niches, except that sort of implies they just move around to where there is room and live there. In actuality, most ecosystems are complexly intercoupled systems where many species depend on other species, etc., so each fills various roles and has various needs.

Page 21, lines 29-31: What existing threats could be reduced if �soil moisture increases or the incidence of freezing conditions is reduced -- ? Again this is looking at the bright side with no real facts to indicate why. Please provide an example and citation to support this assertion.

Response: It would seem self evident that an increase in soil moisture could alleviate stresses in a number of types of systems (although for other species the same change could create stresses). However, the text has been modified to remove the reference to �threats to biodiversity. --

Page 21, lines 35-37: Citation required.

Response: A reference to the underlying report has been added.

Page 21, lines 39-45: Again I point out that extinction of one species is not ameliorated by the expansion of another.

Response: Agreed. No change needed.

Page 22, line 2: It might be better to word this as, ��further depleting� --

Response: Change made, with indication it applies to only some lakes.

Page 22, Potential adaptation options to ensure adequate water resources: There needs to be some discussion of protection of natural ecosystem water needs.

Response: In addition to a phrase being added to those already included, the nature of the impacts is mentioned in previous subsections, and the new subsection makes clear that adaptation options are most limited for natural ecosystems.

Page 22, lines 26-28: What criteria will be used to determine when and to what degree �social, equity and environmental considerations -- will be addressed?

Response: As for most situations involving adaptation, that is likely to be best decided at the local to regional level.

Page 23, Temperature related illness and death: Some discussion of heat stress with air pollution is needed. It has its own section later but you need to allude to it here.

Response: A phrase was added to indicate that the identified stresses could act individually or in combination.

Page 23, line 20. �While analyses suggest � -- This sentence does not make logical sense. If we have no confidence in our estimated projections of the potential impacts of climate change on health how can we be confident that the problems can be dealt with?

Response: The opening phrase has been deleted and a phrase making the point has been added to the second sentence of the paragraph.

Page 23, line 26. While it is true that ��uncertainties remain about how the climate will change and how environmental conditions may change -- , it is also true that many estimates and projections about climate change have been made and a consensus by scientists of a range of plausible outcomes for future climate has been reached (IPCC TAR 2001). Therefore projections of the extent and direction of potential impacts of climate variability and change on health, while difficult, are by no means impossible and have in fact been made in the documents this report refers to. This paragraph is unnecessarily emphasizing the �uncertainties -- and not fairly reporting the scientific conclusions.

Response: In this chapter we are talking about the potential consequences within the US, as opposed to internationally. Within the US, our communities, institutions and lifestyles tend to be designed in ways to make us less vulnerable to environmental stresses than those living in other nations, and additional adaptation measures are typically taken to deal with additional stresses. Given this situation and the underlying reports, we think making the points about uncertainties is quite appropriate.

Pages 23-27 Climate Interactions with Human Health

This five-page section appears to have three key findings:

� First, �[P]rojections of the extent and direction of potential impacts of climate variability and change on health are extremely difficult to make with confidence. -- (page 23, lines 21-22)

� Second, [S]ignificant outbreaks of these diseases as a result of climate change are unlikely because of US health and community standards and systems. -- (page 27, lines 4-5).

� Third, [A]daptive responses are desirable from a public health perspective irrespective of climate change. -- (page 27, lines 40-41).

However, these results are easily lost in the five pages of text on climate and human health. This section should be edited to highlight these findings.

Response: Because the issue of human health receives so much attention, we believe that care needs to be taken in explaining the issues involved and how the conclusions are reached (and qualified). With respect to highlighting these three points, a change in the first sentence makes this point more obvious and the third point is the lead-off sentence in a key paragraph. As to the second point, it is not meant to imply that the risk is being reduced, only that we are likely to continue to be reasonably protected, even if perhaps a bit less so and with more effort.

Page 23, line 27 to 30. This conclusion -- that the balance between increased risk of heat-related illness and decreased risk of cold-related illness cannot be confidently assessed, does not adequately summarize what is discussed later in the chapter, namely that extreme heat causes more deaths than any other category of deaths attributable to extreme weather. In addition, as discussed later in the chapter (page 24), while some winter deaths are related to cold weather (e.g., slipping on the ice), many are related to infectious disease, which may or may not decrease with milder winters. This would suggest that increased heat would have more negative effect than decreased cold.

Response: Although discussed more completely in the underlying materials, the key issue here is that current trends in building design, warning systems, and use of air-conditioning are reducing exposure to heat stress. Thus, although heat stress may be potentially more important if no other changes were taking place, all else is not equal, and exposure is being reduced. This complication of changing exposure makes it very difficult to evaluate with confidence what the changes may be, and even whether there is likely to be an increase in deaths due to heat stress in the future.

Page 24, lines 31-32: A better discussion of the timing of winter death is needed, especially after the statement on page 23 which indicates that heat is the most detrimental extreme weather. Some discussion of causes (unrelated to temperature) involving winter death is made but perhaps a more thorough examination is needed.

Response: Unfortunately, there is insufficient information to provide the necessary analysis. It is for this reason that EPA is planning to sponsor research and assessment activities to get a better handle on this question.

Page 25, line 25: This vague reference to �ongoing changes in technology -- is not useful. It provides no real information and is nothing more than hopeful handwaving. The only example that is provided in the paragraph pertains to regulatory improvements, not technology.

Response: Examples of potential technological steps that could have dramatic effects on air quality include fuel cells, electric cars, flywheel cars, natural gas-powered vehicles, nuclear power plants, and lots more. This does not seem the appropriate place to enumerate all the possibilities.

Page 26, lines 1-2: Is this decline U.S. only? How large is �dramatic -- ? Is there a citation?

Response: This was meant to refer to the US, as this chapter is about impacts on the US. A phrase is added to make this clear. As for other materials in this chapter, reference can be made to the underlying documents, but this conclusion seems obvious for the US.

Page 26, lines 19-20: How does this increase relate to the decrease discussed in lines 1-2?

Response: As the sentence indicates, the increase mentioned here relates to marine related illnesses, which have been a small part of the incidences compared to the start of the 20^th century that involved freshwater supplies, etc. In addition, the numbers are quite modest.

Page 26, lines 26-28

This text makes a passing reference to Figure 6.9. This Figure provides an excellent example of the importance of economic and cultural factors conditions in climate/health issues. Additionally, public health systems also are likely to be important in explaining the radical difference in disease rates on two sides of the border, and public health systems are not specifically mentioned in the discussion. The example of dengue in Texas versus the Mexican border states should be referenced more explicitly in the text. Figure 6.9 also should be retained in the final report because it clearly demonstrates the potential of adaptation in addressing some of the risks of potential climate change.

Response: �public health systems -- have been added to the text. Because of how figures and captions will be displayed, we believe this will give this figure the prominence it deserves.

Page 27, line 15: It is customary to write the entire genus name the first time it is mentioned in a document.

Response: This change has been made.

Pages 28-29 -- Climate Change Impacts in Various Regions of the United States

This section and the accompanying tables (Tables 6.1 and 6.4) should be deleted. First, the types of potential impacts discussed in the National Assessment reports have been amply discussed in the first 28 pages of this Chapter. Second, the premise of the National Assessment regional results --- that meaningful regional assessment is currently possible --- is faulty as discussed earlier. Third, the existence of the Clinton Administration National Assessment is noted elsewhere.

Response: We respectfully disagree with each part of this suggestion. With respect to the first point, while the types of consequences have been generally discussed in this chapter (and this section does not repeat those points), the potential consequences differ in character across the US, and there is significant interest in what types of vulnerabilities and outcomes may be most important in which parts of the country. With respect to deleting the tables, although Table 6.1 simply indicated which regions have been studied (and provides a reference to widely prepared and reviewed reports), this table has been deleted to shorten the chapter. Table 6.4 summarizes the key issues in the briefest possible form and has been kept.

With respect to the second point, this was addressed in response to the general comments on this point. That we do not know the details of the climate change does not mean either that there will be no change nor that we cannot gain some insight by considering how the types of change projected will interact with local conditions. Therefore, we believe the regional analyses have significant value and provide useful insights.

This Assessment was carried out by a wide diversity of experts of very diverse background and affiliation; the teams were to a large extent independent and leadership responsibility for regional assessments, for example, was provided by universities in the region. The Assessment was not at all based on political perspective and this charge is inappropriate and irrelevant.

Page 36, Table 6.2 -- Key national level findings from the US National Assessment

This table appears to be pulled from the US National Assessment and should be replaced with a similar table that: 1) follows the organization and content of the material actually presented in Chapter 6; and 2) emphasizes the key findings covered in the Overview (pages 1-2) including the importance of a healthy economy as well as an adaptive economic and social structure that responds to changes as evidenced by behavioral changes that occurred during the 20^th century.

Response: In that this chapter is drawn from the materials prepared as part of the National Assessment (which provide the underlying basis for all of the sections), and in that this chapter is not itself an assessment, it seems most appropriate to include the set of findings from the National Assessment, largely as presented. The findings themselves and the current ordering of them already reflect the second point above about adaptability by, for example, indicating that the food supply for the US is secure.

Page 36, Line 1: Should read: Key findings adapted from the US Nat'l Assessment

Response: Change made.

Page 36, Line 20: After the last sentence add: However, increases in agricultural and forest productivity might reduce pressures on habitat and ecosystems, and for greater fragmentation.

Response: This point has been already made, and the text as phrased here is so speculative that it does not seem to merit inclusion in the set of key findings.

Page 36, Line 22: Should read: Drought is an important concern virtually everywhere although its effects on vegetation (including crops and forests) might be mitigated by increased water use efficiency due to higher CO2 levels.

Response: In that drought has effects that reach to sectors beyond vegetation, it would seem that adding this statement to the findings would make it both too long and incomplete. However, this is a good point and it has been added to the text in the section originally on page 21.

Page 36, Item #5. The current crop models which form the basis of the statement that climate change will be beneficial to US agriculture here do not adequately incorporate the effect of extreme events (floods, droughts), pests and pathogens, and other factors as described in the body of the National Assessment and this summary. In addition, the models assume that increased carbon dioxide will translate into sustained increases in productivity, an assumption that cannot be supported by the short-term studies done to date.

Response: It is true that the current models do not explicitly treat all of the indicated factors as well as is desired. However, the US agricultural system has proven itself so well that surpluses are the primary difficulty, even accounting for exports. Thus, the NAST felt it appropriate to conclude that the US food supply would be secure given the successful record of adaptive and productivity enhancing measures that have been found in the past.

Page 37, Line 5: Should read: Other stresses affected by climate change.

Response: Using the word affected is so vague as to be meaningless. There are a number of stresses where magnification is the likely result, so this text is left unchanged.