12.11.07
Posted in Science, Transportation
at 11:25 am
This is a follow-up to my earlier post about Monbiot’s book on climate change. In that post, I stated that I was interested in long-term emissions targets because they will probably constrain transportation planning over the course of my career. Now that I’m looking at the issue more closely, I’ve found some relevant research: a great report from Robin Hickman and David Banister in the UK, Visioning and Backcasting for UK Transport Policy or VIBAT. (Reference courtesy of Todd Litman, VTPI.) It looks at the transport problem in the UK through a similar lens as Monbiot, but with considerably more rigour. For the record, VIBAT is not yet published in a peer-reviewed journal, although it has been presented at academic conferences. To date, I have only read the executive summary and skimmed the rest.
Domestic transportation in the UK emitted 39 MtC/year (megatonnes of carbon per year) in 1990, the Kyoto baseline. It rose slightly to 41 MtC/year by 2000, and is projected to rise to 52 MtC/year by 2030 in a “business-as-usual” scenario. A recent Department for Transport white paper suggested new policies for the UK, and projected that the 2030 level would be 38 MtC/year if those policies were adopted, a very small reduction from 1990 levels.
Hickman and Banister took a more dramatic approach. They chose a target of 60% reduction in domestic UK transportation emissions by 2030 from the standard 1990 baseline, aiming for a 15 MtC/year emissions level. This is not Monbiot’s target of a 90% cut by 2030, but it’s still an ambitious choice, somewhat more aggressive than the official UK goal of 60% by 2050.
In the early framing of the paper, the problems of air travel are abundantly clear: UK international air emissions are currently 8 MtC, and might be projected to rise to 20 MtC by 2030. I can’t imagine a scenario where it would be politically acceptable for air travel to be given a bigger slice of emissions than all domestic transportation. As the authors state, “Reducing carbon emissions from international air travel should be a priority for research and action.” In the report, they focus on domestic emissions alone, and leave air travel and international shipping outside their scope.
The authors came up with two scenarios for the policy climate in 2030.
- A “New Market Economy” where the emissions target is met with a minimum of change in behaviour. This is achieved by investing heavily in hybrid vehicles and alternative fuels, and hoping that adequate technology can be developed.
- A “Smart Social Policy” vision where behavioural change is the central strategy instead of technology. Carbon savings are achieved by shorter trips, lower speed limits, and a broad package of policies.
Hickman and Banister assembled a package of policies that would be deployed under each scenario, “backcasting” to find appropriate policies that match the vision. They found that the “New Market Economy” vision could not meet the carbon targets and fell ~10 MtC short, even with optimistic assumptions regarding future technology. The main reason for this was the ongoing growth in car travel: a business-as-usual scenario of +35% in travel would require a massive technological fix. By contrast, the policies that were politically acceptable in the “Smart Social Policy” vision were adequate for the task.
The figures below summarize the emissions changes (in MtC/year) associated with the policies in each package. Click to enlarge and see them side-by-side. (Sources: Fig. 4 and 5, Executive Summary. Resized to matching scales.)
These results don’t particularly surprise me, but it’s still unusual to see a prominent academic like David Banister putting his name beside such a bold policy proposal. Beyond the usual recommendation of further research, the authors do attach one major caveat to their result: they have assumed that the policies they recommended do not interact and result in synergies. That’s a whopper; it’s entirely possible that synergies would result. Finally, I haven’t personally reviewed the assumptions associated with their emissions estimates; I’m sure many of them have a big margin of error. Still, while the exact impact of each policy is unknown, I wouldn’t be surprised if overall conclusion is still accurate: behaviour change will probably be necessary.
One side note tying back to my Monbiot posting, the Smart Social Policy vision required on two enabling measures: higher oil prices (either globally or locally due to taxes) and carbon rationing. I was surprised to see carbon rationing included in mainstream academic discussion, but it is apparently making inroads in the UK. (The main reference seems to be Meyer Hillman and Tina Fawcett’s book, How We Can Save the Planet published by Penguin.)
Finally, here are some pictures that quickly summarize the projections for modal share in the different scenarios:
The size of each box tells you have many kilometers each person is projected to travel using each mode in a given year. This says nothing about emissions, just how far people travel and what mode they use for their travel. I like this visualization: it emphasizes the reduction in travel in the Smart Social Policy scenario. The scales on the left are for the two bars, indicating the carbon emissions and vehicle efficiencies in each scenario. (I’ve made one correction, indicated like [this]: they forgot to include the 10 MtC/year shortfall in the New Market Economy scenario.)
For reference, here are historical modal shares. The 2030 projection shown below represents the white paper policy projection, not the “business as usual” BAU scenario with 52 MtC/year emissions.
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12.06.07
Posted in Site News
at 9:14 pm
In the wake of the Facebook explosion, I’ve been thinking more about my public/private face on the web. This site started as a personal site with some professional sidelines, like my old work in computer graphics and my transportation bibliography. However, I’ve decided that I want this to primarily be my professional face to the world, and so I’m splitting the blog in half. This is mostly just for cleanness of presentation, avoiding littering my professional site with personal cruft.
My personal posts will now be at personal.davidpritchard.org; please visit at your leisure, update your bookmarks and add the new side to your feed reader. My professional posts will remain on this site. If you do want to read both, you can just subscribe to both, or use the blended feed.
As part of this reorganization, I’m also going to start publishing a feed of news clippings I find interesting. Both the professional and personal sites have an additional feed on the right that you can subscribe to if you’re interested. The professional one is focused on transportation and land use articles, while the personal one has more entertainment, web miscellanea and politics. Also, in case you missed the addition, my personal site has a list of movie reviews in the sidebar (using the same plugin as Eric).
Finally, if you’ve never tried using feeds and “subscribing” to blogs, I encourage you to try it out (click on the “Entries” link at the top right of the site). Google Reader is a great tool for following blogs, and it makes it far easier to absorb information from far-flung corners of the web. You can read more about it on Wikipedia.
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11.29.07
Posted in Science, Books
at 3:26 pm
I’ve recently finished reading George Monbiot’s Heat: How to Stop the Planet from Burning. It’s an interesting piece from a widely-syndicated journalist, and it left me both alarmed and unsatisfied. I’ve held back on writing about it until I had a chance to read up a bit more on the underlying science and discuss the topic with more knowledgeable types, but I think I’m ready to comment.
For the anonymous visitors to this page, let me preface this by saying that I have zero expertise in this topic; I have no climate science training, and this represents my first stab at investigating the area. I am interested in this subject largely in terms of its implications for transportation/land use policy: to decide suitable long-term policies, I need a reasonable idea of the likely long-term acceptable level of carbon emissions.
At its heart, I think the book must be understood in terms of its intended audience: the environmental movement. Monbiot’s book is a call-to-reason for the movement, a plea to avoid the “aesthetic fallacy” of pleasing but impractical solutions: think high-speed rail, biofuels, voluntary conservation, or exclusive reliance on solar/wind power. He also urges some revisiting of traditionally demonised technologies, such as nuclear power and carbon sequestration. On these terms, the book is a valuable shaking-up of traditional environmental viewpoints. After establishing a target for emissions cuts, he devotes most of his book to investigations of the feasibility of current technologies for achieving these targets. His discussion of air travel and “love miles” is particularly prescient. The context for his book is exclusively the United Kingdom, and the solutions he proposed cannot necessarily be directly transferred elsewhere.
In this posting, I want to focus more on Monbiot’s target. He based the book on a simple argument, originally published in a 2006 column he wrote for The Guardian, which you can read yourself.
- A global temperature rise higher than 2°C would likely mean runaway positive feedbacks and unstoppable large amounts of warming.
- If we want mean global temperature rises no higher than 2°C (with 70% probability), we need to aim for atmospheric concentrations of CO2 to stabilise at ~380ppm (or CO2-equivalent gases at 450ppm).
- Stabilisation requires emissions (sources) to equal absorptions (sinks). Land-based ecosystems’ ability to absorb carbon drops at higher temperatures. This will reduce the total land+ocean sink from past levels (4 GtC/year) to 2.7 GtC/year. Note: 1 GtC means “Giga-tonne of carbon”.
- Therefore, we need to cut annual global emissions by 60% to 2.7 GtC/year.
- Furthermore, this cut needs to be completed by 2030.
- Finally, if emissions are to be fairly distributed to individual nations on a per capita basis, then the UK needs to cut its emissions by 90%. Monbiot argues in favour of a carbon rationing system with an equal emission entitlement for each individual.
I’ve dug around a little to see how valid these assumptions are. As far as I can tell, Part A is extremely poorly understood, with both likely positive and negative feedbacks, of unknown relative magnitude. For one, the Intergovernmental Panel on Climate Change (IPCC) has not made any claims along these lines. Is it possible that runaway feedbacks will occur? Certainly ― we just have little idea of how likely it is. If you belong to the pessimistic wing of the environmental movement, you may find it easy to accept runaway feedback; the rest of us will have to treat it as a thought experiment and a worst-case scenario.
Part B sounds broadly reasonable. Like part A, part C is very poorly understood at present, but his choice of figure is in line with current estimates of the sink’s reaction to temperature. The target level in part D appears to roughly match with current estimates of the necessary “equilibrium” emissions level, but he assumes that we only work on the emissions end, and he doesn’t consider potential improvements of the performance of sinks. More importantly, the timeline in E appears to be unnecessarily aggressive and I can’t really establish the basis for this choice of target date; Monbiot relies on this near-future deadline to reject any new technological developments, but this is probably not entirely valid. Nevertheless, while the near-future deadline is not as tight as Monbiot claims, changes do need to be made quite soon.
Finally, part F conflates environmental needs and social justice ― admirable and probably necessary in the longer-term, but dreaming of a level of international fairness that is historically unparalleled. There are also “fair” solutions that may be precluded by such an approach: suppose Northern countries paid for the construction of highly efficient new infrastructure in Southern countries. It is possible that such a strategy might be equally fair and more cost-effective than retrofitting existing infrastructure in the North, but it is excluded from consideration by Monbiot’s approach to fairness. In some ways, Monbiot’s conception of an “equal ration” looks like a conservationist’s dream: it forces everyone to learn to conserve energy and carbon. Still, given the magnitude of the change that Monbiot believes necessary, his argument that only equal rations would be politically viable is fairly credible. He drew an analogy to rationing during World War II: in times of great hardship, conservation of scarce goods is unlikely to work if some parts of the population (e.g., the rich countries) were excluded.
In support of my analysis, allow me to introduce exhibit B: a peer-reviewed paper tackling the same topic. (Disclaimer: I came across this paper after it was referenced by RealClimate in their review of Al Gore’s movie. It’s a fairly reputable blog run by climate scientists.)
- Stephen Pacala and Robert Socolow (2004). “Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies”, Science 305:968-972. PDF and supplementary online material.
Before looking at their differences, I would first like to emphasise the similarities between this paper and Monbiot’s argument. Pacala and Socolow considered target atmospheric CO2 concentration levels of 500±50 ppm (Monbiot: 380ppm), aiming to restrain global carbon emissions at current levels (7GtC/year) from now until 2054 and then decreasing to ~2-3.5 GtC/year by 2125 (Monbiot: 2.7GtC/year by 2030). The paper aims to show that emissions can be reduced using currently available technologies that have already been proven at an industrial scale. Like Monbiot, they based their projections largely on the IPCC’s 3rd Assessment Report (AR3) from 2001, and do not include information from 2007’s 4th Assessment Report. They assumed a weak land+ocean carbon sink of 2.4 GtC/year (Monbiot: 2.7 GtC/year). They proposed many of the same tools to reduce carbon output: reduced use of vehicles, more efficient vehicles, efficient buildings, reduction of coal usage, additional nuclear and wind power, and/or carbon capture and storage at remaining coal plants. However, unlike Monbiot, they suggested that a small subset of this list of technologies would be adequate, and they considered technologies unsuitable for the UK like solar power. Finally, they agreed with Monbiot that air travel is particularly difficult to decarbonise.
Let me start with their graphs of different emission reduction scenarios, taken from page 41 of their supplementary material:
The top graph shows different scenarios for how much carbon humans emit; the bottom graph shows the resulting atmospheric carbon level. The black line here represents “business as usual,” and each pair of coloured lines represents a different target stable carbon level. The effect of delaying reductions is clear: to achieve the same stabilization level, a more aggressive reduction rate is required. The final stable global emissions level is roughly 2-3.5 GtC/year, in the same ballpark as Monbiot’s target level (2.7 GtC/year), but achieved between 2100 and 2150 instead of aiming for a 2030 deadline. In their main paper, they focus on the 500ppm early reduction scenario. They omit any discussion of the associated temperature rises; my understanding is that a 450ppm target means a rise of 2.1°C (range: 1.9° to 3.1°), and a 550ppm target means a rise of 2.9°C [IPCC AR4 p. 791].
Pacala and Socolow devoted a good deal of text in their supplement to the discussion of terrestrial carbon sinks, emphasising the huge lack of knowledge in this area, which is quite interesting. I won’t continue to belabour the differences between Monbiot and Pacala and Socolow, but I would encourage you to read both. Pacala and Socolow are particularly worthwhile, although considerably harder to read and understand. From Pacala and Socolow’s work, it looks like a 60% cut from today’s global emissions is probably necessary, but may not need to be complete until closer to the end of the century. Aggressive reductions would still be needed today to have any hope of reaching that target. Finally, while the ultimate share of emissions may not be strictly equal per capita, it’s a safe bet that the cut for carbon-intensive economies (like the UK, Canada or the USA) will be considerably higher than 60% ― perhaps not the 90-94% that Monbiot suggests, but it’s hard to imagine that anything less than 70% would work. I make no claims that this is a “scientific” estimate; it is simply my educated guess on the basis of a very cursory reading of the literature.
Unfortunately, Monbiot’s aggressive deadline (2030) and a set of drastic assumptions make his book feel alarmist. While there is indeed much to be alarmed about, his book really feels like the edge of despair; the proposals are so extreme that they make the task appear insurmountable. (For a good discussion of alarmism in popular discussions of climate change, see RealClimate’s positive review of another interesting book, Six Degrees.) I’m inclined to describe Monbiot in the same way that RealClimate commenter Lou Grinzo described James Howard Kunstler: “I’m increasingly convinced that […] Kunstler is intentionally yelling fire in the theater because that’s the only way to alert enough people to a situation that could, with enough indifference, turn into a real conflagration.”
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10.10.07
Posted in Science, Transportation
at 4:05 pm
Mike passed me a recent report from the Intergovernmental Panel on Climate Change (IPCC) Working Group III (Mitigation of Climate Change). The IPCC is quite famous for its reports summarising the scientific consensus on climate science, so I was curious to see what the process and results of their follow-up reports looked like. I only read the transport chapter, since it’s the part I understand.
Overall, it’s a decent summary of current understanding of transportation trends, which is difficult to do at an international level with a wide spectrum of urban forms and demographics. The report includes a summary, and working group members vote on each paragraph to establish the level of knowledge and agreement on the report’s conclusions. One paragraph in particular struck me:
Providing public transports systems and their related infrastructure and promoting non-motorised transport can contribute to GHG mitigation. However, local conditions determine how much transport can be shifted to less energy intensive modes. Occupancy rates and primary energy sources of the transport mode further determine the mitigation impact. The energy requirements for urban transport are strongly influenced by the density and spatial structure of the built environment, as well as by location, extent and nature of transport infrastructure. If the share of buses in passenger transport in typical Latin American cities would increase by 5–10%, then CO2 emissions could go down by 4–9% at costs of the order of 60–70 US$/tCO2 (low agreement, limited evidence).
[page 326, emphasis added]
I’m a little shocked that this paragraph garners low agreement and is considered to be backed by limited evidence. (I’ll exclude the final sentence, since I don’t know anything about that particular study.) The paragraph is already weakened by many words indicating uncertainty - “can contribute” … “local conditions” … “could go down” etc. But there isn’t even consensus with the weakened wording. I emphasised the one sentence on density and spatial structure - my personal research interest. Again, I’m astounded that there is still wavering about this subject.
That sentence represents one of the report’s only discussions of urban form. It appears occasionally elsewhere in the chapter, but the framing unfortunately focuses on transportation, and treats land use as fixed - a massive oversight. While there are occasional mentions of the value of “co-ordinating” transportation and land use, these are not quantified and do not make it into the conclusions of the report. There is a separate chapter on housing, but it focuses on building construction and energy consumption, again omitting urban form. As so often in the past, urban structure is forgotten and falls into the cracks between disciplines.
The report sensibly treats the US as a “special case” in the international context, since it’s so low density. (e.g., increasing transit service in many US cities could plausibly increase GHG emissions - if no new riders are attracted but more buses are on the road). But it’s a double-edged sword - it suggests that US cities can continue to follow an auto-dependent path, since the report doesn’t contemplate changing land use.
At the end of the day, though, the main problem is the inconclusiveness of the research - the focus on the exceptional context of the USA has too often limited researchers from observing the clearer trends in other parts of the world. Integrated land use/transport models are still too immature for this type of policy analysis, and international comparison studies remain plagued by data incompatibilities. Finally, the field rarely presents its results in a policy-relevant manner - I have never seen a transportation/land use report that estimated the cost of a policy in terms of US$/tCO2-equivalent. It’s unfortunate - researchers in fields like biofuels are doing a lot of work to estimate greenhouse gas reductions, and their results are immediately relevant to policymakers.
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