Currently Skimming:
3 Review of Individual Sections
3 Review of Individual Sections
Pages 13-58
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 13... ...
." The "Key Findings" section of the Executive Summary is organized as a partial outline of the chapters with a selection of bullets that have been taken -- sometimes verbatim -- from key findings throughout the chapters of the SAP. Within the context of the SAP chapters, these bullets are understandable; but, as presented in the Executive 13
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From page 14... ...
The key findings also include a lot of repetition; for example key findings on global and polar ozone based on observations are provided under ES.3.2 and repeated under ES.3.4. The authoring team should consider focusing on key statements of the future only in ES.3.4.
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From page 15... ...
7, L 153: There are significant ozone losses in the tropical stratosphere, as discussed in the WMO report (2007)
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From page 16... ...
11, L 245-247: The text implies that one model predicts worsening Arctic ozone depletion.
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From page 17... ...
CHAPTER 1: INTRODUCTION In Chapter 1 of the draft SAP, the background information on ozone should be expanded and revised to accommodate readers who may not have technical knowledge in this area. The committee provides some suggestions below for improving the presentation of this background information.
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From page 18... ...
Examples include: carbon dioxide warms the troposphere but cools the stratosphere; lower temperatures increase ozone in the upper stratosphere, but decrease ozone (for current halogen loading) in the polar lower stratosphere; ozone depletion and climate change are distinct issues, but they are related both in terms of physical processes and policy (e.g., trade-offs)
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From page 19... ...
Rather than focusing on the chemical mechanisms, a single figure could be inserted instead that is more useful for policymakers, simply illustrating that anthropogenic halogens cause stratospheric ozone depletion (perhaps in a top panel) and illustrating that anthropogenic nitrogen oxide (NOx)
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From page 20... ...
Major Comments Background information should be presented at the beginning of the draft SAP Chapter 2, perhaps defining concepts and incorporating parts of the key issues section, before presenting the key findings. As part of this background information, the authoring team should add a box in either SAP Chapter 1 or the introduction to SAP Chapter 2 to explain the life cycle of fluorochemicals, define consumption, and explain the relationship between production, consumption, emission, atmospheric concentrations, and EESC or radiative forcing.
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From page 21... ...
• A simple explanation of how atmospheric concentrations are calculated from emissions. • A simple explanation of how radiative forcing is calculated from concentrations.
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From page 22... ...
29-34: Key Findings Section should address the key issues.
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From page 23... ...
o In the U.S., HFC-23 emissions and total HCFC-22 production are reported annually to the EPA in aggregate. o The EPA vintaging model should capture the refrigerant and fire extinguishant HFC-23 emissions.
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From page 24... ...
possessed smaller uncertainties. The authoring team should consider including a figure from the WMO report (2007)
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From page 25... ...
The authoring team should consider including something like a cartoon of a box model with a simple equation. Also, this box derives atmospheric mixing ratios of ODSs owing to U.S.
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From page 26... ...
the large polar ozone losses in the lowermost stratosphere, as well as the relative roles of transport and chemistry in causing ozone changes in the mid-latitude lower stratosphere. Some mention should be made of the different methods of observing/monitoring ozone loss at these two altitude regimes.
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From page 27... ...
are at least reasonably consistent with the fact that this drastic ozone loss did not occur. That, in and of itself, could help the authoring team relate its findings to human activities, such as the international regulation of halogenated compounds under the Montreal Protocol, as required in the SAP prospectus.
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From page 28... ...
o L 2887-2888: What is the reference for the statement that ozone depletion is the dominant contributor to long-term and zonal-averaged UVB changes?
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From page 29... ...
To convey this point, the authoring team should consider the following options: a) Top panel, departures 305 nm; middle panel, ozone column departures; bottom panel, the logarithm of the uv305/uv324 ratio.
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From page 30... ...
The draft SAP leaves the impression that Figure 3.16 may be just ozone columns over the United States in a different guise. The draft SAP suggests the controlling property for the UV irradiance estimates is total ozone, with differences between UV305 nm and erythemal irradiance only dependent on how each of these scales with total ozone.
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From page 31... ...
models. Despite this uncertainty, 3-D models currently reproduce the basic features of the Antarctic ozone hole and Arctic ozone losses using previous laboratory recommendations for photochemical parameters (e.g., WMO, 2003; WMO, 2007)
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From page 32... ...
. Hence, bromine may play a more important role in polar ozone depletion than previously thought.The BrO + ClO cycle is now estimated to contribute up to half of total chemical loss of polar ozone, even considering the more efficient ozone loss by the ClO dimer cycle.
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From page 33... ...
110, L 2202: To make a clear distinction from Arctic ozone loss and to avoid any potential misunderstanding, the term "Antarctic" should be added each time the ozone hole is mentioned.
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From page 34... ...
These same gases, Cl and Br, are also responsible for polar ozone loss but at a lower altitude and through different chemistry. Since oxygen atoms (O)
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From page 35... ...
In the Earth's polar regions, a different set of halogen catalyzed reactions is responsible for the dramatic seasonal ozone losses observed over Antarctica during August through October each year (with more than 50% of the total column ozone depleted) and to a much smaller extent over the Arctic during February through March each year.
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From page 36... ...
If the latter, the bottom panel looks like zero ozone loss starts in 1964 (when EESC was very small)
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From page 37... ...
, the March average in 2004/2005, reflectings the strong influence of dynamics (e.g., vortex fragments moved outside the 63°-90° region during March, see Figure 3.4) , and is consequently high relative to those of other recent cold winters even though the magnitude of chemical ozone loss in the lower stratospheric vortex in mid winter 2004/2005 was as high as or higher than in those yearsozone loss in other recent cold winters.
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From page 38... ...
The authoring team should provide clarification on the EESC fit and cumulative ozone loss here.
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From page 39... ...
131, Figure 3.10: This figure, which compares relative rates of Arctic and Antarctic ozone depletion, disguises the fact that, for cold Arctic winters, chemical loss of column ozone in the Arctic is comparable to chemical loss of column ozone in the Antarctic. That is because Figure 3.10 disguises the situation that the Antarctic starts out with so much less ozone than the Arctic.
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From page 40... ...
Try: "The chemical ozone loss processes precipitated by the presence of halogens are initiated by the formation of PSCs in the extremely cold polar lower stratosphere (refs.)
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From page 41... ...
cross section on our understanding of polar ozone loss is von Hobe et al.
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From page 42... ...
The text suggests that there is a major puzzle in our understanding. In fact, CCMs seem to get upper stratospheric ozone losses that are quite consistent with SBUV(/2)
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From page 43... ...
CHAPTER 4: OZONE EFFECTS ON CLIMATE The purpose of Chapter 4 of the draft SAP is to examine the relationships between human impacts on ozone and the changes occurring in the climate system. Overall, the chapter does a good job of capturing the main issues, but the presentation of these issues should be improved.
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From page 44... ...
. In the WMO report, one of the key findings linking climate change to ozone is Figure 4-3 (WMO 2007)
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From page 45... ...
" is likely jargon to a general audience. The authoring team should consider including a statement like "coupled models of the Earth's atmospheric chemistry and climate processes (called chemistry climate models, CCMs)
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From page 46... ...
173, L 3566-3569: Although the impact of ozone depletion on tropospheric climate is outside the scope of this report, it is listed here as a key finding.
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From page 47... ...
To improve this synthesis, Chapter 5 would benefit from a more critical discussion of scenarios and models, as well as a presentation of the updated model results that were prepared by the scientific community for the WMO's Scientific Assessment of Ozone Depletion: 2006 (WMO 2007)
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From page 48... ...
. This should be discussed in SAP Chapter 3, and the implications of this certainly have relevance for the United States and pertinence for modeling and attribution of climate change (i.e., observed ozone changes cannot be imposed and reversed in line with EESC as a scenario to force climate models in the 21st century)
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From page 49... ...
207, L 4338: The text implies that one model predicts worsening Arctic ozone depletion.
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From page 50... ...
210-211, L 4412-4414: That the indirect radiative forcing due to ozone loss falls to zero before the direct RF does is merely a point of definition; that is how the indirect RF is defined (rather arbitrarily)
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From page 51... ...
And note that there is a lot of uncertainty associated with the 1980 baseline. (This does not refer to the fact that ozone loss begins earlier, but rather that the use of the 1980 baseline requires statistical acrobatics which lead to unreliable estimates of the ozone depletion.)
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From page 52... ...
to ozone depletion (EESC) and climate change (radiative forcing)
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From page 53... ...
The SAP would also benefit by including a discussion about the interrelationships between ozone policy and climate policy, both for the United States and internationally. More specifically, the SAP does not address the fact that limiting future emissions of methane is a "win-win" situation, in that methane affects ozone depletion and climate change.
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From page 54... ...
in UV levels over the past three decades because effects of clouds and aerosol have likely masked the increase in UV due to ozone depletion over this region. For "ground stations," the authoring team should consider provide more detail, such as the number and location of these stations.
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From page 55... ...
2005. Indicators of Antarctic ozone depletion.
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From page 56... ...
2007. Chapter 4: How do climate change and stratospheric ozone loss interact?
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From page 57... ...
2007. Scientific Assessment of Ozone Depletion: 2006.
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