Report by UK

First Order Draft, Assessing Transformation Pathways:
UK
This is over 400 scenarios, how many models have been used for creating these? Are all models approximately similarly represented, or are some models strongly overrepresented? Elaborate here or elsewhere (section 6.2.5?), so that the intra vs inter model differences become clearer. Would be good to have statistics on models vs targets (i.e. a matrix that shows climate categories on one axis and model names in another, then populate with numbers of targets run by given models)
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
What explains the below one index for cat 1 mitigation costs for the partial equlibrium models? Is it because most (in comparsion to the cat 3 scenarios) of their costs occur post-2050?
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
Figure not readable.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
See previous comment, I suggest the figure is removed.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
See the previous comment, I suggest the figure is removed and replaced with a short explanation. More detailed results on low carbon technologies follow in any case. If it seems absolutely necessary to include a figure, I'd rather see a single figure showing (for 2050) the low carbon share (or absolute numbers, if this otherwise get too close to the figures that follow later) on one panel and total primary energy in another.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
This figure, while very nice in theory, is not readable in its current form. The letters, especially, are nearly impossible to read, make the figure very messy and I would therefore strongly recommend removing them (it's also impossible to read any colours for the letters). An option might be to just indicate the base year and final year of each transition path (with climate target dependent markers?), so that the time element could be kept in the figure.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
As with the previous figure, the letters are not visible and make the figure messy. I don't think they're really necessary either, as it doesn't seem that important to know which model has produced a certain path. Finally, might be worthwhile to consider some alternative division of fuels as currently most of the figure is empty (because solids having such low shares on the end use level).
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
Also here I would suggest removing the letters and replacing them with simple markers. Especially if it's expected that more scenarios will be included for the SOD.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
The definitions for the technology variation scenarios need to be explained already here. Currently they are included in the following figure (6.30)
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
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This figure is mostly empty space and therefore mainly communicates that there are a couple of outlier scenarios in which land use related CO2 mitigation is especially strong. If this is not the only message that the reader should get from this figure (especially the left panel), I would recommend altering the figure.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
I don't think it's necessary to show explicitly the results for individual models; the figure gets very messy and difficult to read. Show specific ranges instead, for the three milestones years and for the two scenarios.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
This figure doesn't seem very necessary: The logic of the emission trajectories doesn't differ significantly from those of delayed participation scenarios (which are included in the previous figure), even if they are produced differently (and may have more/less optimal emissions in the short term). Add also these scenarios to figure 6.34, or alternatively create two figures, one with full where and when flexibility and one with non-optimal mid term emissions (delayed particip
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
Figure not readable.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
Figure not readable.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
Cross reference this with what's said on page 45, lines 19-22 (and shown in figure 6.26?). Presumably the difference could be explained by the different time horizons (2100 vs 2050) and/or by significant differences in total final energy use between the climate categories? Please clarify, in any case.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
How do you explain the wide range of cat 4 cumulative emissions for 2000 to 2100? The range, in terms of forcing, should be only 1 W/m2 for this category (4-5 W/m2), but the cumulative emissions can almost triple and climate consequences would still be consistent with cat 4? Surely non-CO2 gases alone can't explain this and the significant overlap with cat 5? Please elaborate.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
what do the diagonal lines represent?
View full comment by Nina Meddings...

First Order Draft, Assessing Transformation Pathways:
UK
what do the diagonal lines represent?
View full comment by Nina Meddings...

First Order Draft, Assessing Transformation Pathways:
UK
Considering the enormous uncertainties of such an economy wide, decades long transitions, I would think there's more "gap" than what we do know for certain. This isn't really a "proper" gap, of course, as it is not possible to acquire information or data that would be able to fully fill this gap. I still think it's important to make this clear, i.e. what is currently listed here are gaps for incrementally improving the modelling of the scenarios, but they will in no way remo
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
Stochastic scenarios, with uncertain long term targets, should also be mentioned, as they explicitly investigate the relationship between mid and (uncertain) long term targets. Already the TIAM family of models alone has published at least 3 papers on such scenarios and there must be other models that have been used in similar fashion (refereces to the TIAM papers: Syri, Lehtilä, Ekholm, Savolainen, Holttinen and Peltola. Global energy and emissions scenarios for effec
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
This section is currently rather generic, but still rather long. In light of the fact that the authors suggest there will be a number of additions for the SOD, I would suggest cutting down text that overlaps strongly with other chapters (or even sections within this chapter, e.g. some of energy conversion, land use related text).
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
Most of this section discusses AR4 approach to sectoral analysis, which doesn't seem necessary, especially to the extent that it's currently done (i.e. over a page) AND taking into account the length of the current draft.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways:
UK
good synthesis of the sectoral analyses but some sub-sections lack comparison with transformation pathways. Specifically "Energy Conversion", "Transport" and "Human Settlements" sub-sections
View full comment by Nina Meddings...

First Order Draft, Assessing Transformation Pathways: From Page 0
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When it comes to economic impacts the study concentrates on outputs GCE and partial equilibrium models that often include only one economic sector. I could not find a section that explains the shortcomings of these model types and how the outcomes are impacted by the theoretical underpinnings of these models nor giving a reasoning why these types of models should be preferred. And there is no explanation of why other model types were excluded. In one place the chapter concent
View full comment by Annela Anger-Kraavi...

First Order Draft, Assessing Transformation Pathways: From Page 0
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It is some time since I look at the “Stabilisation Scenarios” literature and will confine my comments to the following general points. Though it is carefully worded, Chapter 1 comes close to saying that 2 deg.C is now almost impossible: does Chapter 6 analysis support this? Consistency is important. It would be great – albeit difficult – if Chapter 6 could make more connection between the sectoral chapter studies and the global scenarios. Does bottom-up meet top-
View full comment by Michael Grubb...

First Order Draft, Assessing Transformation Pathways: From Page 0
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It's a bit unfortunately that the dataset, and therefore most of the analysis, was not finalized for the FOD. There are findings across the chapter that would in their current form require some clarifications/explanations, but it doesn't seem useful to ask for such at the moment, when there is always a caveat close by, suggesting that the analysis so far shouldn't be taken too seriously.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 0
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More references should be added, throughout the chapter, to results that are currently referenced using a project name (e.g. EMFXX, RECIPE etc) only.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 0
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The scenario ensemble used for the chapter appears to somewhat dominate the discussion, especially in some sections. This is also demonstrated by the fact that in certain sections a proper literature review is almost completely missing and the references mostly focus on the few large studies that also feed in to the database (and in which a number of the authors have been involved). While this is a useful approach in terms of giving detailed information about a large set of s
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 10 , Line 13 To Page 10 , Line 15
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This contradicts what was said previously about feasibility being subjective (beyond the biogeophysical constraints). If it's truly subjective, how could this chapter provide information about near term actions that prevent certain long term goals (except for the near term actions that break the long term goals already in the near term, of course)? And to follow the logic of the previous paragraph, does this chapter discuss perceptions of feasibility, rather than actual feasi
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 11 , Line 26 To Page 11 , Line 35
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This is extremely vague and not convincing. Using two scenarios instead of one would "contain information" about uncertainty , a truism, but would tell little about what uncertainties the differences between these two scenarios reflect, how complete is the coverage of uncertainties, how the differences can be interpreted and what interpretation are clearly out of reach. Or in other words, if there is full, formal information about uncertainty in one end of a range and no inf
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 12 , Line 11 To Page 14 , Line 4
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As the chapter is currently some 20 pages longer than it should be, I suggest this section on the tools is cut down considerably. The descriptions on the trade, foresight etc dimensions of the models should be summarized much more concisely and more references could be given instead. I don't see why it would be necessary to give this much detail when the results are anyway analysed mostly on the level of the full scenario ensemble. I also suggest removing table 6.1. complete
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 17 , Line 15 To Page 17 , Line 17
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Or more precisely, there is evidence that *incremental* change may not be enough, if all the other assumptions remain in place. One can easily imagine baseline scenarios in which emissions would dip due to, for example, a revolutionary, low cost carbon free technology emerging. As the baselines are often created as a reference point for mitigation scenarios (as was pointed out earlier in the draft), such a baseline would be somewhat purpose defeating (and optimistic, of cours
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 18 , Line 10 To Page 18 , Line 11
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I think it's noteworthy that there is not a single documented "degrowth" baseline scenario, not even on the regional level. This is noteworthy also in terms of how well the existing baseline scenario ensemble might capture the "full", relevant baseline scenario space.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 20 , Line 11 To Page 20 , Line 11
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I assume this is meant to say that there's no unique definition for representing concentration targets in the models? If correct please rephrase, if incorrect please explain.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 21 , Line 17 To Page 22 , Line 1
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There's something wrong with the sentence starting "Cumulative…". Neither table 6.3 nor figure 6.7 shows cumulative emissions either.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 22 , Line 27 To Page 22 , Line 27
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The reference should be to figure 6.9, I believe.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 22 , Line 29 To Page 22 , Line 31
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There's nothing about non-CO2 gases in section 6.2.1. Correct the reference.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 22 , Line 7 To Page 22 , Line 9
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Does this mean that the baselines are not included in any of the categories? I would have thought that category 6, for example, would mostly have baseline scenarios in it (forcing being above 7 W/m2).
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 23 , Line 17 To Page 23 , Line 17
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Write out GTP.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 23 , Line 9 To Page 23 , Line 9
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Write out GWP.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 25 , Line 18 To Page 25 , Line 18
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This reference is not in the bibliography.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 25 , Line 43 To Page 25 , Line 43
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Figure 6.11, instead of 6.8
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 25 , Line 46 To Page 25 , Line 47
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Is there a reference for this analysis?
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 31 , Line 11 To Page 31 , Line 12
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it would also be important to acknowledge that cost estimates are already such a specific indicator that the large uncertainties visible in the model outcomes are probably dwarfed by the uncertainties that are unavoidable, when complex systems (e.g. global economy, innovation and technology development etc) are projected far into the future (i.e. level of knowledge concerning, not only probabilities, but also possibilities. Modelling of disruptive surprises, which are almost
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 32 , Line 16 To Page 32 , Line 22
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As mentioned previously, I would expect the the energy (and other) systems of 2100 to look quite different from the ones today, no matter whether a mitigation target is assumed or not. Also mentioned previously: It's hardly surprising that there's less variation when the absolute distance from the reference point (i.e. the baseline) is smaller, especially if one expects, as was suggested, the costs (as a function of the target) to increase faster than linearly.A lower variati
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 33 , Line 31 To Page 33 , Line 34
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Isn't this a bit too self evident to count as a finding?
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 35 , Line 35 To Page 35 , Line 37
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This sentence is unclear - the 20% reduction would lead to 0.5-2.0% of what? Presumably change in welfare; if so, please spell this out in the text
View full comment by David Joffe...

First Order Draft, Assessing Transformation Pathways: From Page 35 , Line 36 To Page 35 , Line 37
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Does "the lowest possible cost" here refer to using a single carbon price? If yes, make sure the terminology agrees with what is on page 30, lines 40-44.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 36 , Line 11 To Page 36 , Line 12
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Figure is missing (6.17 shows something completely different, as does 6.18)
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 36 , Line 16 To Page 36 , Line 17
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I'm not entirely sure I understand this; to me all the CAT scenarios appear to have similar costs (i.e. circle areas), no matter what is assumed for FES. Or does this conclusion refer to the size of the "non-mitigation" circle vs "mitigation" circles, in order to point out that just reducing gasline use with FES, without achieving significant emission reductions, would cost ~ quarter of what it would cost to achieve at least as significant gasoline use reductions AND more mea
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 37 , Line 31 To Page 37 , Line 31
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Same effects as what?
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 42 , Line 20 To Page 42 , Line 33
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As the chapter is currently too long, I suggest this paragraph and the figure 6.24 that follows is cut. It's hardly surprising that emissions from fossil fuels strongly correlate with non-CCS related primary energy use of fossil fuels, nor that both go down with mitigation (or that there still can be variations across the scenarios). Sacrificing nearly a page to this does not seem necessary.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 43 , Line 7 To Page 43 , Line 26
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Like the preceeding paragraph on fossil fuels, I find also these paragraphs (and the figure that follows) rather trivial and unnecessary. If must be possible to make in less than nearly two pages the rather simple point that mitigatio reduces the use of fossil fuels, increases the use of low carbon energy and, all else being equal, increases low carbon use even further if demand is high.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 430 , Line 46 To Page 431 , Line 1
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It is not clear here what the intent of the comment on geoenegineering is in this case. What sort of reference will be made to geoengineering at this point?
View full comment by David Santillo...

First Order Draft, Assessing Transformation Pathways: From Page 449 , Line 35 To Page 449 , Line 35
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Is it fair to say that all proposed geoengineering strategies constitute adaptation? I'm not sure this is such a clear association
View full comment by David Santillo...

First Order Draft, Assessing Transformation Pathways: From Page 47 , Line 6 To Page 47 , Line 7
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The title of section 6.3.7.3. is rather convoluted.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 48 , Line 17 To Page 48 , Line 23
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The importance of CCS has a 4th category: its application to carbon-intensive industry, especially those like cement and iron&steel that produce CO2 via chemical processes as well as fossil fuel combustion and that cannot therefore be largely decarbonised by using renewable or nuclear. Also, a further energy vector that can be produced in combination with CCS is synthetic natural gas.
View full comment by David Joffe...

First Order Draft, Assessing Transformation Pathways: From Page 49 , Line 17 To Page 49 , Line 23
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A wide range of energy system models include the possibility to switch parts of the transport system to electricity and/or hydrogen. Rather than citing one integrated model that does incorporate this possibility, would it not be more sensible to say that the rest tend to overstate the costs of mitigation because they ignore such important options?
View full comment by David Joffe...

First Order Draft, Assessing Transformation Pathways: From Page 5 , Line 28 To Page 5 , Line 29
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The wording is a bit courageous. Surely not ALL countries MUST bring their emissions "toward zero" for meeting ANY stabilization goal? Reformulate.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 5 , Line 30 To Page 5 , Line 32
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I'd suggest moving this conclusion later in the paragraph - currently mitigation quantities and costs are brought up before they are properly defined (i.e. only after the conclusion it's explained that costs and quantities are calculated against a baseline, not, for example, the base year)
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 5 , Line 43 To Page 6 , Line 5
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The conclusion here seems to suggest that the scenario results can be used as proof for when emissions need to peak. I don't find this convincing, as this depends completely on the assumptions that have been used when constructing the models (which is acknowledged in the table caption that follows, but not in the text). For example, if a break through for cheap air capture technologies was assumed in the models, the peak could presumably be later. At the very least I would li
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 502 , Line 24 To Page 502 , Line 26
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It is worth qualifying this sentence with the preface "if it was to be effective in practice, the net effect would be to accelerate...etc....".
View full comment by David Santillo...

First Order Draft, Assessing Transformation Pathways: From Page 502 , Line 28 To Page 502 , Line 30
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It is important that the boundaries of this cost estimate are made explicit, i.e. does this simply include the cost of the iron, or also the cost of transporting, deploying, monitoring imacts and effectiveness, etc. Costs depend on so many factors that it is important not to prejudge cost of what remains an abstract concept.
View full comment by David Santillo...

First Order Draft, Assessing Transformation Pathways: From Page 502 , Line 43 To Page 502 , Line 43
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It is probably worth noting here that ocean fertilisation activities are now controlled under the London Convention/London Protocol Resolutions LC-LP.1(2008), which disallows all ocean fertilization activities other then legitimate scientific research, and LC-LP.2(2010), which established the assessment framework to determine whether proposed ocean fertilization activities constitute legitimate scientific research (http://www.imo.org/blast/mainframemenu.asp?topic_id=1969). I
View full comment by David Santillo...

First Order Draft, Assessing Transformation Pathways: From Page 502 , Line 46 To Page 503 , Line 1
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Proposals for alkalinity management do not strinctly accelerate weathering but rather aim to mimic the effect of such enhanced weathering through artificial addition. In addition to concerns regarding impacts of mining, processing and trasmporting on land, the Expert Group report for the CBD SBSTTA on "IMPACTS OF CLIMATE-RELATED GEOENGINEERING ON BIOLOGICAL DIVERSITY" (UNEP/CBD/SBSTTA/16/INF/28, http://www.cbd.int/doc/meetings/sbstta/sbstta-16/information/sbstta-16-inf-28-en
View full comment by David Santillo...

First Order Draft, Assessing Transformation Pathways: From Page 502 , Line 4
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This entire section would benefit significantly from greater consideration of potential adverse impacts of commonly proposed geoengineering methods, drawing perhaps on the recent report of the Expert Working Group on impacts of geoengineering on biodiversity under the CBD (http://www.cbd.int/doc/meetings/sbstta/sbstta-16/information/sbstta-16-inf-28-en.pdf)
View full comment by David Santillo...

First Order Draft, Assessing Transformation Pathways: From Page 503 , Line 17 To Page 503 , Line 21
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There are also significant concerns regarding the potential environmental impacts of the most commonly used or proposed amine-based capture chemicals, e.g. Padurean, A., Cormos, C.-C., Cormos, A.-M., Agachi, P.-S. (2011) Multicriterial analysis of post-combustion carbon dioxide capture using alkanolamines. International Journal of Greenhouse Gas Control 5: 676-685 .
View full comment by David Santillo...

First Order Draft, Assessing Transformation Pathways: From Page 503 , Line 23 To Page 503 , Line 23
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It is unwise at this stage to state in an unqualified way that SRM has a role in shaping climate policy as it is not clear that it would be effective in any manner, or acceptable as a policy approach. It may be expected to act relatively quickly in reducing solar radiation reaching the Earth's surface, but the speed, uniformity and effectiveness of action remains unknown.
View full comment by David Santillo...

First Order Draft, Assessing Transformation Pathways: From Page 503 , Line 26 To Page 503 , Line 27
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once again this is a highly theoretical treatment and should be explicitly so - it cannot yet be said that SRM 'CAN' temporarily and imperfectly maskclimate change - these are, of course, theoretical modelled prediction,s not empirical observations.
View full comment by David Santillo...

First Order Draft, Assessing Transformation Pathways: From Page 503 , Line 34 To Page 503 , Line 34
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In fact, there is little evidence that public understanding of SRM is growing 'rapidly' - without stressing that public awareness understanding is starting from (and remains at) a very low baseline, this statement could be misinterpreted as implying commen knowledge and perhaps even widespread acceptance.
View full comment by David Santillo...

First Order Draft, Assessing Transformation Pathways: From Page 504 , Line 21 To Page 504 , Line 29
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This paragraph is also currently quite unclear in significant parts and will need to be reviewed in detail once the text has been redrafted and the meaning is clear
View full comment by David Santillo...

First Order Draft, Assessing Transformation Pathways: From Page 504 , Line 6 To Page 504 , Line 16
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This paragraph is currently very unclear, with some sentences being very long and others incomplete. It also implies once again that SRM is demonstrably able to compensate for changes in temperature or precipitation, without making clear that these are 'in principle' theoretical statements based on limited modelling. In some cases, the model outputs have been tuned by specfici inputs in order to compensate, and it is vital that model parameters and outputs are also distingu
View full comment by David Santillo...

First Order Draft, Assessing Transformation Pathways: From Page 51 , Line 36 To Page 51 , Line 38
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This message doesn't come through very strong from the figure and I wouldn't add a reference to it in this sentence. It would be much more appropriate later, for example for the sentence on lines 39 and 40 ("However…")
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 53 , Line 19 To Page 53 , Line 21
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This should also be mentioned on page 48, lines 17-23. Currently bioCCS is mentioned as one of three reasons why CCS is important for 450 ppmCO2eq, but this text here suggests that the three reasons mentioned are unlikely to be equally significant.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 59 , Line 32 To Page 59 , Line 38
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For the models implementing e.g. learning curves, it would also be useful to indicate whether they assume perfect foresight with intertemporal optimization. This is likely to have a big impact on model decisions, as the model knows the "winning technologies" beforehand (i.e. no uncertainty) and knows also how much having these technologies is worth in the future (i.e. there is no uncertainty about anything else, such as climate target, either).
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 6 , Line 13 To Page 6 , Line 15
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The wording is again too brave. Nobody knows what WILL happen in the scope of an almost 100 year long transition. These are model outcomes, reflecting very specfic sets of assumptions and the conclusions should be framed with that in mind (i.e. do not reformulate model outcomes as forecasts, but keep it clear that the statement about "predictions or forecasts" (page 15 line 6) is still valid)
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 6 , Line 25 To Page 6 , Line 27
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The range of model outcomes (which I assume this refers to) does not automatically provide a mapping of real life uncertainties. Also, as mitigation costs are a function of the baseline AND the cost range understandably increases the further away one is from the baseline, couldn't one alternatively interpret this range as reflecting the uncertainties of the baselines? Finally, one would expect the energy (and other) systems of 2100 to be quite different from those of today,
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 60 , Line 8 To Page 60 , Line 8
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Should the numbers 1-6 be replaced with references?
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 61 , Line 7 To Page 61 , Line 8
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Give references.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 63 , Line 14 To Page 63 , Line 15
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Meaning not clear to me
View full comment by Nina Meddings...

First Order Draft, Assessing Transformation Pathways: From Page 64 , Line 21 To Page 64 , Line 25
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This should be cross referenced with what is being said on page 36, lines 7-17 (suggesting that cap-and-trade mitigation is more expensive if it's combined with instruments targeting subsystems) and on page 30, lines 9-13 (emission price does not reflect full costs of mitigation, if additional policies affecting emissions are in place).
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 65 , Line 1 To Page 65 , Line 2
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This statement needs to be made more clearly. Is it meant to say that a given, non-minimized cost can be achieved with a number of technical systems? Or, in case least cost systems are discussed, should "identical" be preceeded with the word "nearly"? And why does this all depend on whether endogenous technical change is allowed?
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 65 , Line 40 To Page 65 , Line 45
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These seem like a rather courageous claims and presumably depend completely on how some of these benefits have been monetized. More references supporting these are needed, in any case, and I would even then suggest a more careful formulation, due to the difficulty of comparing costs against benefits that are non-trivial to monetize.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 65 , Line 41 To Page 65 , Line 41
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Reference is not included in the bibliography (or, alternatively, the given publication year is wrong_
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 65 , Line 7 To Page 65 , Line 11
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There are some incomplete sentences on these lines.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 66 , Line 9 To Page 66 , Line 9
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Unclear what/where this "table 1" is. First table in section 6.5 shows R&D needs.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 67 , Line 16 To Page 67 , Line 16
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Unclear what/where this figure 1" is. First figure in section 6.5 shows technology specific cost trajectories.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 67 , Line 22 To Page 67 , Line 22
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6.2.3. is interpreation of model infeasibility. Probably 6.3.3. was meant?
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 70 , Line 11 To Page 70 , Line 11
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Should be table 6.7.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 71 , Line 21 To Page 71 , Line 21
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The reference is incorrect; the authors of the cited paper are Strachan and Usher.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 75 , Line 22 To Page 75 , Line 34
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As mentioned earlier, CCS is a key option for decarbonisation in a number of important industry sectors. This is especially true for those sectors, such as cement and iron&steel, that cannot be fully decarbonised with renewables or nuclear, as some of their CO2 output results from chemical reactions
View full comment by David Joffe...

First Order Draft, Assessing Transformation Pathways: From Page 8 , Line 20 To Page 8 , Line 20
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Write out CDR, as it appears here for the first time.
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 8 , Line 3 To Page 8 , Line 6
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Although I do not seriously doubt this conclusion, I don't think it can be made based on the model outcomes. In other words, technology alone will not bring emissions down unless one expects technologies capable of doing this to emerge and implements them in the model (i.e. low cost, carbon free, high potential technologies. A very optimistic fusion scenario, for example). The current observation is somewhat circular and just indicates that virtually nobody has created such
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 8 , Line 46 To Page 9 , Line 1
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I assume this comment has been left in accidentally?
View full comment by Ilkka Keppo...

First Order Draft, Assessing Transformation Pathways: From Page 85 , Line 14 To Page 85 , Line 14
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should this say "increase costs" rather than "reduce costs"?
View full comment by Nina Meddings...

First Order Draft, Assessing Transformation Pathways: From Page 9 , Line 2 To Page 9 , Line 2
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Replace "will" with "would". Few things currently suggests that we are on that trajectory.
View full comment by Ilkka Keppo...

Breakdown for UK