IPCC AR5 WGI Chapter 14 - A Review
Climate Phenomena and their Relevance for Future Regional Climate Change
Chapter Assessment
Chapter 14 is tasked with summarizing projected changes in major climate phenomena that are relevant to understanding future regional climate change. On the whole, the chapter does a pretty good job of this. Importantly, it is very logically organized and the chapter sections build nicely upon one another. After an introduction of the major concepts, each climate phenomenon (monsoons, cyclones, ENSO, etc.) is summarized in succession, culminating in the final section on future regional climate change that incorporates the aforementioned information on climate phenomena to make region-specific statements on future temperature and precipitation changes. I think this works very well as the last chapter of the Working Group I report because it synthesizes all of the data and model projections discussed earlier in the report in a regional framework to address impacts on a more local and relevant scale to many policymakers. However, although the individual sections on climate phenomena build up to the concluding regional section nicely, I would have liked to see a section presenting a more coherent global picture. Much time was spent describing how changes in these climate phenomena will affect regional climate in the future, but there was not much discussion of how these different climate phenomena interact with each other on the global scale and what impacts would result from those interactions.
On the level of individual chapter sections, there are some places where things were done very well and other places where I think there are shortcomings and/or things could be improved. Starting with the executive summary, I think the content (i.e. what they decided to highlight in the most important part of the chapter) could have been improved. Monsoons, tropical phenomena, and cyclones were summarized well, but the remainder of the summary focused on other, more specific modes of climate variability that I think are less relevant to policymakers than the key statements from the future regional climate change section, which were excluded from the executive summary. I think the introduction did an excellent job of laying the essential conceptual groundwork for the rest of the chapter, especially through Box 14.1.
Each of the more substantive portions of the chapter had at least a few positives and shortcomings. The monsoon chapter, for example, did a very good job of explaining the physical understanding behind links between monsoon dynamics and climate change (see FAQ 14.1). However, this section did not do a particularly good job of identifying and explaining the model limitations associated with their projections for each of the major monsoons, especially for the American and African systems. In cases where the limitations are mentioned, the wording remained vague and no specific examples were presented. In addition, there could have been a bit more policy relevance weaved into this section given the fairly obvious implications of changes in monsoon precipitation.
I believe that the section on ENSO did a particularly good job of going through the relevant concepts associated with this important phenomenon prior to delving into the model projections. However, I feel that the figures presenting the model results could have been better. There is considerable discussion within this section about the varying amplitude of ENSO, both in the past and in the projected future, but there was no figure that clearly demonstrated this point. The subsequent section on cyclones, in contrast to the monsoon section, did a really good job of weaving in some points on policy relevance with the model projections. For example, the section emphasized the projections of frequency of the most intense cyclones, recognizing that this metric “is generally more important to physical and societal impacts than overall frequency or mean intensity” (pg. 1249). The cyclones section also did an exemplary job explaining the underlying uncertainties with the model projections.
Lastly, I think the regional climate change sections are very well done. Each region-specific subsection is clear, concise, and well organized. The summary paragraphs at the end of each subsection are particularly helpful, as they highlight the salient model projections for each region. The one area that this section could have been improved is the figures. The figures are only presented for a small subset of the regions, and all of them show changes in precipitation (and not temperature). While it would be unreasonable given the stringent space requirements to produce a figure for each region, a bit more variety in terms of precipitation versus temperature models would have helped. However, I think the biggest omission is the lack of a summary figure that in some manner illustrates the changes region by region. There is a long table at the end of the chapter that does this to some degree, but I think it would have been beneficial to the reader to see these changes in a more visual manner.
Overall, I think this chapter accomplished what it set out to do, but could have been improved slightly with more emphasis on model limitations/uncertainties, more coherence between the individual sections by way of a synthesis paragraph or two, and improved figures.