Review of the U.S. Climate Change Science Program's Synthesis and Assessment Product 3.3, "Weather and Climate Extremes in a Changing Climate" (2007) / Chapter Skim
Currently Skimming:
3 Review of Individual Sections
3 Review of Individual Sections
Pages 7-25
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
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From page 7... ...
. In some cases, the specific suggestions that follow the overarching thoughts further relate to issues raised in the Major Comments; in other cases, these specific suggestions are targeted and the committee considers the issue a relatively minor one.
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From page 8... ...
• Line 18: Please see comment on Line 220 regarding the use of the phrase "hurricane activity." • Line 21: Longer duration aggravates the impacts of heat waves, droughts, downpours, and to some extent tropical cyclones. This paragraph should be modified to reflect this consideration, consistent with statements in the body of the SAP.
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From page 9... ...
• Line 66: This sentence on problems of climate models simulating extremes is correct, but it is not obviously related to the previous two sentences, which describe that changes in climate averages imply changes in the tails of the distribution and hence in climate extremes. Perhaps a more direct connection could be made or the sentence put in a separate paragraph where the difficulties for models in simulating extremes are elaborated a little, including both resolution and process limitations.
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From page 10... ...
• Line 205: Section 4.3 boldly asserts increased evapotranspiration and decreased spring runoff in the mountains without providing any compelling evidence. First, it is likely that potential evapotranspiration will increase because of warmer air temperatures but actual evapotranspiration will decrease because of decreased soil moisture.
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From page 11... ...
. Unless the trends in conditions are shown, this statement should be restricted to simply state that the data are not adequate to make definitive statements about trends in severe thunderstorms and tornadoes.
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From page 12... ...
. CHAPTER 1 Why Weather and Climate Extremes Matter Weather and climate extremes matter primarily because of their socio-economic and environmental impacts, yet the Chapter does not discuss socio-economic impacts in any significant detail.
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From page 13... ...
time of the first snow melt (earlier in the Sierras means longer dry season with far reaching impacts on the ecology)
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From page 14... ...
• Line 562: The sentence beginning on this line could be interpreted as a value judgment that compares human worth and suffering to animal or plant worth and should be deleted or phrased more precisely. CHAPTER 2 Observed Changes of Weather and Climate Extremes In this chapter the authors address the key issues set forth in the document's prospectus regarding what is known about observed changes in extreme events.
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From page 15... ...
In considering these comments, the authors should strive to capture the dimensions of the ongoing scientific debate vis-à-vis trends in tropical cyclones and climate change, while considering the need to limit the length of the discussion. Specific Comments and Suggestions: • Line 69: This finding is inconsistent with earlier statements about drought (Line 17 of the Abstract and Line 193 of the Executive Summary)
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From page 16... ...
Does the comment refer to multi-decadal variability? • Line 643: The annual-average global total of 90 with a variance of approximately 10 is consistent with Poisson statistics, and indeed a range of studies provide no compelling evidence to reject a Poisson model (Gray 1968; Katz 2002; Frank and Young 2007)
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From page 17... ...
Again, this is a point that would be essential in a review targeted at a professional audience, but it does not serve the purpose here. • Line 998: The lack of an increasing trend in landfalling Atlantic tropical cyclones is important.
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From page 18... ...
• Line 1296: The committee believes that in fact there are data over the central North Pacific to analyze extratropical cyclones; it may be limited, but it exists. • Line 1352: This statement is not supported by Figure 2.36, which indicates no trends whatsoever.
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From page 19... ...
Moreover, the discussion on tropical cyclones is excessively lengthy while drought receives less attention than it should. The committee understands that although hurricanes are of considerable interest to a wide variety of audiences, the socio-economic implications of increases in droughts and heat waves are also very serious.
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From page 20... ...
should be discussed. This statement on the changes in vertical wind shear appears to be based on the ensemble mean model result from one study.
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From page 21... ...
• Line 427: In addition to comparing observations to the ensemble mean of climate model output, these types of comparisons should address ensemble spread and differences in the spatial patterns among ensemble members. All that is required for the observations to be consistent with the model ensemble is that the observed trend and spatial pattern of change lies within the full range of the model ensemble members, but not necessarily close to the ensemble mean.
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From page 22... ...
Differences in the spatial patterns are likely due to natural climate variations at regional scales. • Line 1262: The introductory material is excellent, although here and elsewhere, the authors should reconcile the disconnect between model predictions of reduced tropical cyclone numbers due to increased shear with the subset of the observations that support increased numbers.
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From page 23... ...
Notwithstanding the recommendation to reduce the amount of discussion within the chapters, the committee suggests that the authors add a recommendation to support research that seeks to improve our understanding of what governs hurricane intensity. Current theory (e.g., the Maximum Potential Intensity)
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From page 24... ...
If the authors are raising ETCs and extreme wave heights for a particular reason and they wish for Recommendation 3 to remain separate, then those particular reasons should be further elucidated. • Line 133: This recommendation should be broadened to included paleo datsets that can be used to infer time series of extreme hydrologic flows (paleogeological datasets)
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From page 25... ...
Insert "to enhance spatial and time resolution" before "to recreate." In addition, this recommendation should be consistent with what appears in the document (see text beginning on line 175 of the Executive Summary) and should further recommend use of, or consideration of, regional climate models.
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