Author: Tom Fid

  • Sea Level Roundup

    Realclimate has Martin Vermeer’s reflections on the making of his recent sea level paper with Stefan Rahmstorf. At some point I hope to post a replication of that study, in a model with the Grinsted and Rahmstorf 2007 structures, but I haven’t managed to replicate it yet. The problem may be that I haven’t yet tackled the reservoir storage issue.

    At Nature Reports, Olive Heffernan introduces several sea level articles. Rahmstorf contrasts the recent set of semi-empirical models, predicting sea level of a meter or more this century, with the AR4 finding. Lowe and Gregory wonder if the semi-empirical models are really seeing enough of the dynamic ice signal to have predictive power, and worry about overadaptation to high scenarios. Mark Schrope reports on underadaptation – vulnerable developments in Florida. Mason Inman reports on ecological engineering, a softer approach to coastal defense.

  • Who eats the risk?

    From the Asilomar geoengineering conference, via WorldChanging:

    Lesson two: Nobody has any clear idea how to resolve the inequalities inherent in geoengineering. One of the most quoted remarks at the conference came from Pablo Suarez, the associate director of programs with the Red Cross/Red Crescent Climate Centre, who asked during one plenary session, “Who eats the risk?” In Suarez’s view, geoengineering is all about shifting the risk of global warming from rich nations — i.e., those who can afford the technologies to manipulate the climate — to poor nations. Suarez admitted that one way to resolve this might be for rich nations to pay poor nations for the damage caused by, say, shifting precipitation patterns. But that conjured up visions of Bangladeshi farmers suing Chinese geoengineers for ruining their rice crop — a legalistic can of worms that nobody was willing to openly explore.

    If geoengineering is a for-profit operation, it presumably also involves the public bearing the risk of private acts, because investors aren’t likely to have an appetite for the essentially unlimited liability.

  • US manufacturing … are you high?

    The BBC today carries the headline, “US manufacturing output hits 6 year high.” That sounded like an April Fool’s joke. Sure enough, FRED shows manufacturing output 15% below its 2007 peak at the end of last year, a gap that would be almost impossible to make up in a quarter. The problem is that the ISM-PMI index reported by the BBC is a measure of growth, not absolute level. The BBC has confused the stock (output) with the flow (output growth). In reality, things are improving, but there’s still quite a bit of ground to cover to recover the peak.

  • One child at the crossroads

    China’s one child policy is at its 30th birthday. Inside-Out China has a quick post on the debate over the future of the policy. That caught my interest, because I’ve seen recent headlines calling for an increase in China’s population growth to facilitate dealing with an aging population – a potentially disastrous policy that nevertheless has adherents in many countries, including the US.

    Here are the age structures of some major countries, young and old:

    population structure

    Vertical axis indicates the fraction of the population that resides in each age category.

    Germany and Japan have the pig-in-the-python shape that results from falling birthrates. The US has a flatter age structure, presumably due to a combination of births and immigration. Brazil and India have very young populations, with the mode at the left hand side. Given the delay between birth and fertility, that builds in a lot of future growth.

    Compared to Germany and Japan, China hardly seems to be on the verge of an aging crisis. In any case, given the bathtub delay between birth and maturity, a baby boom wouldn’t improve the dependency ratio for almost two decades.

    More importantly, growth is not a sustainable strategy for coping with aging. At the same time that growth augments labor, it dilutes the resource base and capital available per capita. If you believe that people are the ultimate resource, i.e. that increasing returns to human capital will create offsetting technical opportunities, that might work. I rather doubt that’s a viable strategy though; human capital is more than just warm bodies (of which there’s no shortage); it’s educated and productive bodies – which are harder to get. More likely, a growth strategy just accelerates the arrival of resource constraints. In any case, the population growth play is not robust to uncertainty about future returns to human capital – if there are bumps on the technical road, it’s disastrous.

    To say that population growth is a bad strategy for China is not necessarily to say that the one child policy should stay. If its enforcement is spotty, perhaps lifting it would be a good thing. Focusing on incentives and values that internalize population tradeoffs might lead to a better long term outcome than top-down control.

  • Painting ourselves into a green corner

    At the Green California Summit & Expo this week, I saw a strange sight: a group of greentech manufacturers hanging out in the halls, griping about environmental regulations. Their point? That a surfeit of command-and-control measures makes compliance such a lengthy and costly process that it’s hard to bring innovations to market. That’s a nice self-defeating outcome!

    Consider this situation:

    greenCorner
    I was thinking of lighting, but it could be anything. Letters a-e represent technologies with different properties. The red area is banned as too toxic. The blue area is banned as too inefficient. That leaves only technology a. Maybe that’s OK, but what if a is made in Cuba, or emits harmful radiation, or doesn’t work in cold weather? That’s how regulations get really complicated and laden with exceptions. Also, if we revise our understanding of toxics, how should we update this to reflect the tradeoffs between toxics in the bulb and toxics from power generation, or using less toxic material per bulb vs. using fewer bulbs? Notice that the only feasible option here – a – is not even on the efficient frontier; a mix of e and b could provide the same light with slightly less power and toxics.

    Proliferation of standards creates a situation with high compliance costs, both for manufacturers and the bureaucracy that has to administer them. That discourages small startups, leaving the market for large firms, which in turn creates the temptation for the incumbents to influence the regulations in self-serving ways. There are also big coverage issues: standards have to be defined clearly, which usually means that there are fringe applications that escape regulation. Refrigerators get covered by Energy Star, but undercounter icemakers and other cold energy hogs don’t. Even when the standards work, lack of a price signal means that some of their gains get eaten up by rebound effects. When technology moves on, today’s seemingly sensible standard becomes part of tomorrow’s “dumb laws” chain email.

    The solution is obviously not total laissez faire; then the environmental goals just don’t get met. There probably are some things that are most efficient to ban outright (but not the bulb), but for most things it would be better to impose upstream prices on the problems – mercury, bisphenol A, carbon, or whatever – and let the market sort it out. Then providers can make tradeoffs the way they usually do – which package of options makes the cheapest product? -without a bunch of compliance risk involved in bringing their product to market.

    Here’s the alternative scheme:

    greenTradeoffs

    The green and orange lines represent isocost curves for two different sets of energy and toxic prices. If the unit prices of a-e were otherwise the same, you’d choose b with the green pricing scheme (cheap toxics, expensive energy) and e in the opposite circumstance (orange). If some of the technologies are uniquely valuable in some situations, pricing also permits that tradeoff – perhaps c is not especially efficient or clean, but has important medical applications.

    With a system driven by prices and values, we could have very simple conversations about adaptive environmental control. Are NOx levels acceptable? If not, raise the price of emitting NOx until it is. End of discussion.

    Two related tidbits:

    Fed green buildings guru Kevin Kampschroer gave an interesting talk on the GSA’s greening efforts. He expressed hope that we could move from LEED (checklists) to LEEP (performance-based ratings).

    I heard from a lighting manufacturer that the cost of making a CFL is under a buck, but running a recycling program (for mercury recapture) costs $1.50/bulb. There must be a lot of markup in the distribution channels to get them up to retail prices.

  • State of the global deal, Feb 2010

    Somehow I forgot to mention our latest release:

    climatescoreboardFeb10

    The “Confirmed Proposals” emissions above translate into temperature rise of 3.9C (7F) in 2100. More details on the CI blog. The widget still stands where we left it in Copenhagen:

  • The lure of border carbon adjustments

    Are border carbon adjustments (BCAs) the wave of the future? Consider these two figures:

    Carbon flows embodied in trade goods

    Leakage

    The first shows the scale of carbon embodied in trade. The second, even if it overstates true intentions, demonstrates the threat of carbon outsourcing. Both are compelling arguments for border adjustments (i.e. tariffs) on GHG emissions.

    I think things could easily go this route: it’s essentially a noncooperative route to a harmonized global carbon price. Unlike global emissions trading, it’s not driven by any principle of fair allocation of property rights in the atmosphere; instead it serves the more vulgar notion that everyone (or at least every nation) keeps their own money.

    Consider the pros and cons:

    Advocates of BCAs claim that the measures are intended to address three factors. First, competitiveness concerns where some industries in developed countries consider that a BCA will protect their global competitiveness vis-a-vis industries in countries that do not apply the same requirements. The second argument for BCAs is ‘carbon leakage’ – the notion that emissions might move to countries where rules are less stringent. A third argument, of the highest political relevance, has to do with ‘leveraging’ the participation of developing countries in binding mitigation schemes or to adopt comparable measures to offset emissions by their own industries.

    from a developing country perspective, at least three arguments run counter to that idea: 1) that the use of BCAs is a prima facie violation of the spirit and letter of multilateral trade principles and norms that require equal treatment among equal goods; 2) that BCAs are a disguised form of protectionism; and 3) that BCAs undermine in practice the principle of common but differentiated responsibilities.

    In other words: the advocates are a strong domestic constituency with material arguments in places where BCAs might arise. The opponents are somewhere else and don’t get to vote, and armed with legalistic principles more than fear and greed.

  • Feedbackwards

    In the 80s, my mom had an Audi 5000. It’s value was destroyed by allegations of sudden, uncontrollable acceleration. No plausible physical mechanism was ever identified.

    Today, Toyota’s suffering from the same fate. A more likely explanation? Operator error. Stepping on the gas instead of the brake transforms the normal negative feedback loop controlling velocity into a runaway positive feedback:

    … A driver would step on the wrong pedal, panic when the car did not perform as expected, continue to mistake the accelerator for the brake, and press down on the accelerator even harder.

    This had disastrous consequences in a 1992 Washington Square Park incident that killed five and a 2003 Santa Monica Farmers’ Market incident that killed ten …

    Given time, the driver can model the situation, figure out what’s wrong, and correct. But, as my sister can attest, when you’re six feet in front of the garage with the 350 V8 Buick at full throttle, there isn’t a lot of time.

    Read more at the Washington Examiner

  • Idle wind in China?

    Via ClimateProgress:

    China finds itself awash in wind turbine factories

    China’s massive investment in wind turbines, fueled by its government’s renewable energy goals, has caused the value of the turbines to tumble more than 30 percent from 2004 levels, the vice president of Shanghai Electric Group Corp. said yesterday.

    There are now “too many plants,” Lu Yachen said, noting that China is idling as much as 40 percent of its turbine factories.

    The surge in turbine investments came in response to China’s goal to increase its power production capacity from wind fivefold in 2020.

    The problem is that there are power grid constraints, said Dave Dai, an analyst with CLSA Asia-Pacific Markets, noting that construction is slowed because of that obstacle. Currently, only part of China’s power grid is able to accept delivery of electricity produced by renewable energy. “The issues with the grid aren’t expected to ease in the near term,” he said. Still, they “should improve with the development of smart-grid investment over time.”

    The constraints may leave as much as 4 gigawatts of windpower generation capacity lying idle, Sunil Gupta, managing director for Asia and head of clean energy at Morgan Stanley, concluded in November.

    China has the third-largest windpower market by generating capacity, Shanghai Electric’s Yachen said.

    It’s tempting to say that the grid capacity is a typical coordination failure of centrally planned economies. Maybe so, but there are certainly similar failures in market economies – Montana gas producers are currently pipeline-constrained, and the rush to gas in California in the deregulation/Enron days was hardly a model of coordination. (Then again, electric power is hardly a free market.)

    The real problem, of course, is that coal gets a free ride in China – as in most of the world – so that the incentives to solve the transmission problem for wind just aren’t there.

  • Fuzzy VISION

    Like spreadsheets, open-loop models are popular but flawed tools. An open loop model is essentially a scenario-specification tool. It translates user input into outcomes, without any intervening dynamics. These are common in public discourse. An example turned up in the very first link when I googled “regional growth forecast”:

    The growth forecast is completed in two stages. During the first stage SANDAG staff produces a forecast for the entire San Diego region, called the regionwide forecast. This regionwide forecast does not include any land use constraints, but simply projects growth based on existing demographic and economic trends such as fertility rates, mortality rates, domestic migration, international migration, and economic prosperity.

    In other words, there’s unidirectional causality from inputs  to outputs, ignoring the possible effects of the outputs (like prosperity) on the inputs (like migration). Sometimes such scenarios are useful as a starting point for thinking about a problem. However, with no estimate of the likelihood of realization of such a scenario, no understanding of the feedback that would determine the outcome, and no guidance about policy levers that could be used to shape the future, such forecasts won’t get you very far (but they might get you pretty deep – in trouble).

    The key question for any policy, is “how do you get there from here?” Models can help answer such questions. In California, one key part of the low-carbon fuel standard (LCFS) analysis was VISION-CA. I wondered what was in it, so I took it apart to see. The short answer is that it’s an open-loop model that demonstrates a physically-feasible path to compliance, but leaves the user wondering what combination of vehicle and fuel prices and other incentives would actually get consumers and producers to take that path.

    First, it’s laudable that the model is publicly available for critique, and includes macros that permit replication of key results. That puts it ahead of most analyses right away. Unfortunately, it’s a spreadsheet, which makes it tough to know what’s going on inside.

    I translated some of the model core to Vensim for clarity. Here’s the structure:

    VISION-CA

    Bringing the structure into the light reveals that it’s basically a causal tree – from vehicle sales, fuel efficiency, fuel shares, and fuel intensity to emissions. There is one pair of minor feedback loops, concerning the aging of the fleet and vehicle losses. So, this is a vehicle accounting tool that can tell you the consequences of a particular pattern of new vehicle and fuel sales. That’s already a lot of useful information. In particular, it enforces some reality on scenarios, because it imposes the fleet turnover constraint, which imposes a delay in implementation from the time it takes for the vehicle capital stock to adjust. No overnight miracles allowed.

    What it doesn’t tell you is whether a particular measure, like an LCFS, can achieve the desired fleet and fuel trajectory with plausible prices and other conditions. It also can’t help you to decide whether an LCFS, emissions tax, or performance mandate is the better policy. That’s because there’s no consumer choice linking vehicle and fuel cost and performance, consumer knowledge, supplier portfolios, and technology to fuel and vehicle sales. Since equilibrium analysis suggests that there could be problems for the LCFS, and disequilibrium generally makes things harder rather than easier, those omissions are problematic.

    Some other issues come to light as well. Generally, the spreadsheet is of high quality – it’s peer-reviewed heritage and careful construction shows. I only found one issue that I’d consider to be an outright error, but there are some other weaknesses:

    • Fudge factors are used to make confusing units conversions and sweep model-data inconsistencies under the rug. One is used to “correct” for the fact that vehicle fleet dynamics don’t match data, because the fleet is initialized to zero and loss rates are not calibrated.
    • Possible disparities in data streams (e.g., between reported sales and vehicle registrations) are not addressed. In our experience, closed-loop models reveal data problems more often than not. Uncritical use of data in open-loop models permits data problems to go unchallenged.
    • A number of functional relationships in the model are extremely difficult to understand, even for an expert.
    • While the model captures vehicle miles traveled (VMT) variation across vehicle age cohorts, it does not capture VMT variation over time. Since there have been large changes in VMT since the 70s, this would appear to be a significant omission.
    • The treatment of fuel components and blends is rather inflexible (a better outcome can be achieved with arrays in a more structured modeling environment).

    This inventory could be incomplete, because the spreadsheet model contains generic structure replicated across multiple worksheets. Auditing the structure of one sheet doesn’t guarantee that others are sound.

    The bottom line? From a report we wrote detailing our findings (available on request):

    In spite of the issues above, the model seems generally appropriate to the purpose of accounting for physically feasible pathways that achieve efficiency or intensity goals. It seems obvious, though, that physical feasibility is not sufficient for policy feasibility. To develop workable policies and avoid “can’t get there from here” situations, it would be desirable to have a model that linked changes in new vehicle and fuel shares to driving forces (availability, cost, and other elements of attractiveness). That would mean closing a number of feedback loops that are missing from the tree structure above, including:

    • Effects of the LCFS on the internal taxes and subsidies fuel providers would have to impose in order to balance their portfolios

    • Market clearing for fuels, i.e. effects of fuel prices on supply investment incentives and demand for driving, efficiency, etc.

    • Vehicle manufacturer behavior, particularly the incentive to innovate to create new vehicle platforms in response to potential fuel price and consumer preference developments

    • Fueling infrastructure behavior, similar to the above, and perhaps including a geographic component.

    While the structure and parameters defining some of these feedbacks may be uncertain, ignoring them is not a sound alternative. Omitting feedbacks is to assume that they have zero gain – the one value which we know to be wrong.

    It’s actually quite straightforward to construct an alternative model that captures the same dynamics as VISION, but with greater transparency, efficient and flexible use of arrays, calibration to data, and separation of data and structure. That provides a platform for elaboration and exploration of the missing dynamics. It’s possible to have greater dynamic complexity and a more intuitive model at the same time, because a lot of the detail complexity (like annual vehicle cohorts) really isn’t needed for most purposes. We’ve had a number of interesting conversations around a very simple model of transportation, including only a first-order fleet, refining and import capacity, market clearing through fuel price, road congestion, and the consumer’s decision to drive.

    For a really compelling look at the dynamics of vehicles and fuels, my next installment will take a look at Jeroen Struben’s thesis work.

    while the model captures VMT variation across vehicle age cohorts, it does not capture VMT variation over time. Since there have been large changes in VMT since the 70s, this would appear to be a significant omission
  • The Trouble with Spreadsheets

    As a prelude to my next look at alternative fuels models, some thoughts on spreadsheets.

    Everyone loves to hate spreadsheets, and it’s especially easy to hate Excel 2007 for rearranging the interface: a productivity-killer with no discernible benefit. At the same time, everyone uses them. Magne Myrtveit wonders, Why is the spreadsheet so popular when it is so bad?

    Spreadsheets are convenient modeling tools, particularly where substantial data is involved, because numerical inputs and outputs are immediately visible and relationships can be created flexibly. However, flexibility and visibility quickly become problematic when more complex models are involved, because:

    • Structure is invisible and equations, using row-column addresses rather than variable names, are sometimes incomprehensible.
    • Dynamics are difficult to represent; only Euler integration is practical, and propagating dynamic equations over rows and columns is tedious and error-prone.
    • Without matrix subscripting, array operations are hard to identify, because they are implemented through the geography of a worksheet.
    • Arrays with more than two or three dimensions are difficult to work with (row, column, sheet, then what?).
    • Data and model are mixed, so that it is easy to inadvertently modify a parameter and save changes, and then later be unable to easily recover the differences between versions. It’s also easy to break the chain of causality by accidentally replacing an equation with a number.
    • Implementation of scenario and sensitivity analysis requires proliferation of spreadsheets or cumbersome macros and add-in tools.
    • Execution is slow for large models.
    • Adherence to good modeling practices like dimensional consistency is impossible to formally verify

    For some of the reasons above, auditing the equations of even a modestly complex spreadsheet is an arduous task. That means spreadsheets hardly ever get audited, which contributes to many of them being lousy. (An add-in tool called Exposé can get you out of that pickle to some extent.)

    There are, of course, some benefits: spreadsheets are ubiquitous and many people know how to use them. They have pretty formatting and support a wide variety of data input and output. They support many analysis tools, especially with add-ins.

    For my own purposes, I generally restrict spreadsheets to data pre- and post-processing. I do almost everything else in Vensim or a programming language. Even seemingly trivial models are better in Vensim, mainly because it’s easier to avoid unit errors, and more fun to do sensitivity analysis with Synthesim.

  • LCFS in Equilibrium II

    My last post introduced some observations from simulation of an equilibrium fuel portfolio standard model:

    • knife-edge behavior of market volume of alternative fuels as you approach compliance limits (discussed last year): as the required portfolio performance approaches the performance of the best component options, demand for those approaches 100% of volume rapidly.
    • differences in the competitive landscape for technology providers, when compared to alternatives like a carbon tax.
    • differences in behavior under uncertainty.
    • perverse behavior when the elasticity of substitution among fuels is low

    Here are some of the details. First, the model:

    structure

    Notice that this is not a normal SD model – there are loops but no stocks. That’s because this is a system of simultaneous equations solved in equilibrium. The Vensim FIND ZERO function is used to find a vector of prices (one for each fuel, plus the shadow price of emissions intensity) that matches supply and demand, subject to the intensity constraint.

    Each fuel is characterized by a supply curve around a normal price and quantity point. Fuels have a specified true emissions intensity, as well as a measured emissions intensity. The latter might differ from the former because of uncertainty about indirect emissions, for example. Consumers choose among fuels with a specified cross-elasticity. Emissions and other metrics emerge from their fuel choices.

    A run illustrates what happens when we turn this on:

    base+lcfs

    The top panel shows demand, while the bottom panel shows prices. Groups of bars, from left to right, represent each fuel. Three are fossil-based: gasoline from conventional oil, enhanced-recovery oil, and unconventional oil (Venezuelan heavy or oil sands), with increasing emissions intensity. The next three are bio-based (though they could be anything, really): “conventional” which looks like corn ethanol and improves only modestly on gasoline; “better” which is about 2/3 less emissions intensive (and about like California electricity); “transformative” which has near-zero emissions and costs a lot.

    In the base case, demand is met mostly with fossil oils and some conventional biofuel, because these are the cheapest options. Imposing a 20% emissions cut through an LCFS transforms the market from blue to red. The high-intensity fossil fuels are driven out of the market, and a lot more “better” biofuel gets used. Conventional biofuel demand doesn’t increase a lot because it’s not good enough to contribute a lot to meeting the standard.

    The bottom panel shows how this is achieved: fuel providers have to raise the prices of conventional fuels (to suppress demand) and lower the price of low-emission alternatives. Essentially there’s an internal system of subsidies on fuels exceeding the LCFS, and tax on fuels that don’t meet it.

    When you start exploring the behavior of the LCFS and alternatives like an emissions tax, some interesting features emerge. For example, it’s possible to use a tax to achieve the same total emissions as the LCFS, or the same emissions intensity, but not both at the same time. They’re just different instruments. A tax achieves the same total emissions at a lower cost, but higher intensity, than the LCFS does. The difference between matching emissions ($100/ton) and intensity (over $1000/ton) is huge.

    emissions intensity
    Emissions Intensity

    Demand in a tax-controlled market is also distributed quite differently. The tax raises the price of all fuels, because they all have some emissions. As a result, the alternative fuel market is quite a bit smaller, particularly for “conventional” biofuels that have fairly high emissions intensity.

    taxMkt

    When you add uncertainty, things get even more complicated. Consider, for example, the effect of uncertainty about fuel performance. From a regulator’s perspective, just how good is that cellulosic ethanol? Does it contribute to indirect (market mediated) emissions from deforestation? From a provider’s perspective, what intensity do you think the Air Resources Board will assign your product? The emissions of conventional gasoline are pretty well known, but there’s a lot to argue about when it comes to more exotic alternatives.

    Here’s a histogram of true emissions from tax (red) and LCFS (blue) approaches to control, from some Monte Carlo runs with error in assessing the emissions intensity of each fuel:

    trueEmissions

    Notice that I didn’t manage to exactly match the mean outcomes – it could be done, but I didn’t take the time; I just matched the deterministic outcomes. So, problem number one: a deterministic assessment of the market could be misleading.

    Also notice that the LCFS results in a higher variance in emissions (this is also true for intensity). The LCFS amplifies modest measurement uncertainty into big quantity (demand) uncertainties. Here’s the market for “better” biofuels:

    better

    This has interesting consequences for technology developers. If you’re a provider of a new low-carbon fuel, would you like to have a smaller but more predictable market provided by a tax, or the bigger-on-average market provided by the LCFS, with a heavier left tail of bad outcomes?

    I think there are two classes of insight here. First, the equilibrium model shows that there are all kinds of counterintuitive behaviors arising from the intensity constraint in the LCFS. HH&K suggest clever ways to fix some of those. But it’s also important to step back and look at the big picture: the fuel-vehicle market isn’t in equilibrium. Sure, markets for fuels clear day-to-day, and some fuels (like ethanol and gasoline) can be blended to some extent, and thus are highly fungible. But really, a lot of new ideas (high alcohol contents, plug-in hybrids, CNG, fuel cells) require changes to the vehicle fleet and fueling infrastructure to be coordinated with fuel supply itself.

    In that case, it’s rather silly to look only at the short run equilibrium. It’s essential to consider the vehicle fleet and other capital stocks. The general challenge is that the LCFS is not terribly robust to disturbance in the short run (as the uncertainty results above suggest). If decision makers set aggressive targets, and capital stocks don’t move as expected, the resulting short term equilibrium can be rather extreme. That could lead to unravelling of the whole policy. No sensible politician knowingly takes such risks, so a likely alternative is “safe” standards that don’t achieve as much as a robust policy could.

    We actually extended this model to explore capital turnover for a breakthrough fuel startup, but if I told you the details I’d have to kill you. However, I’ll provide some hints in the next post or two on this topic.


    My model isn’t currently cleaned up enough to distribute, but you can get HH&K’s Matlab code. I have no idea how similar the two are, as I haven’t seen the Matlab code (I built my version from the idea expressed in the abstract of an earlier draft, while stuck in an airport on the way to an LCFS workshop).

  • How to critique a model (and build a model that withstands critique)

    Long ago, in the MIT SD PhD seminar, a group of us replicated and critiqued a number of classic models. Some of those formed the basis for my model library. Around that time, Liz Keating wrote a nice summary of “How to Critique a Model.” That used to be on my web site in the mid-90s, but I lost track of it. I haven’t seen an adequate alternative, so I recently tracked down a copy. Here it is: SD Model Critique (thanks, Liz). I highly recommend a look, especially with the SD conference paper submission deadline looming.

  • Dumb and Dumber

    Not to be outdone by Utah, South Dakota has passed its own climate resolution.

    They raise the ante – where Utah cherry-picked twelve years of data, South Dakotans are happy with only 8. Even better, their pattern matching heuristic violates bathtub dynamics:

    WHEREAS, the earth has been cooling for the last eight years despite small increases in anthropogenic carbon dioxide

    They have taken the skeptic claim, that there’s little warming in the tropical troposphere, and bumped it up a notch:

    WHEREAS, there is no evidence of atmospheric warming in the troposphere where the majority of warming would be taking place

    Nope, no trend here:

    Satellite tropospheric temperature, RSS

    Satellite tropospheric temperature (RSS, TLT)

    Skipping over a red herring about Erik the Red,

    WHEREAS, the polar ice cap is subject to shifting warm water currents and the break-up of ice by high wind events. Many oceanographers believe this to be the major cause of melting polar ice, not atmospheric warming

    Now, where could the energy for those warm water currents and high wind events be coming from?

    Next we get the Oregon Petition (you can fact check the signatories yourself using google). Finally, we come to the point:

    NOW, THEREFORE, BE IT RESOLVED, …, that the South Dakota Legislature urges that instruction in the public schools relating to global warming include the following:
    (1)    That global warming is a scientific theory rather than a proven fact;
    (2)    That there are a variety of climatological, meteorological, astrological, thermological, cosmological, and ecological dynamics that can effect world weather phenomena and that the significance and interrelativity of these factors is largely speculative

    Shouldn’t knowing what a theory is and knowing the difference between astrology and astronomy, thermology and thermodynamics be prerequisites for making science education policy?

    You can’t make this stuff up. I guess I’ll have to quit telling North Dakotan jokes now.

  • Sea level update – newish work

    I linked some newish work on sea level by Aslak Grinsted et al. in my last post. There are some other new developments:

    On the data front, Rohling et al. investigate sea level over the last half a million years and in the Pliocene (3+ million years ago). Here’s the relationship between CO2 and Antarctic temperatures:

    Rohling Fig 2A

    Two caveats and one interesting observation here:

    • The axes are flipped; if you think causally with CO2 on the x-axis, you need to mentally reflect this picture.
    • TAA refers to Antarctic temperature, which is subject to polar amplification
    • Notice that the empirical line (red) is much shallower than the relationship in model projections (green). Since the axes are flipped, that means that empirical Antarctic temperatures are much more sensitive to CO2 than projections, if it’s valid to extrapolate, and we wait long enough.

    Looking at the temperature-sea level relationship, they find this:

    Rohling Fig 2B

    The takeaway is:

    Regardless of the uncertainties surrounding the use of any one of the specific scenarios in Fig. 2, it is clear that equilibrium sea level for the present-day TCO2U of 387 ppmv resides within a broad range between 0 and C25 (+/-5) m. The lower limit of that range derives from model projections3, whereas the upper limit derives from data describing the Earth system’s pre-anthropogenic behaviour over the past 0.5-3.5 Myr (this study).

    In other words, if paleo analogies apply, sea level rise might not be fast, but it could get very big.


    Siddall, Stocker and Clark develop a similar nonlinear relationship between temperature and sea level, and use that in yet another simple-model simulation experiment:

    Siddall Fig 1

    I haven’t had a chance to replicate this yet, but it looks like there are two innovations over the Grinsted approach. First, the equilibrium temperature-sea level relationship is nonlinear (s-shaped), as shown above. Second, the time constant of adjustment is asymmetric (potentially faster for ice sheet decay than for growth).

    Siddall et al. find 21st century sea level rise for the A1FI scenario to be 0.82m – a little lower than the Rahmstorf (2007) and Grinsted et al. results I last considered, but still higher than AR4’s 0.59m.

    Update: Whoops, the projections have just been retracted.


    Vermeer and Rahmstorf revisit the 2007 Rahmstorf model, and extend it by including an instantaneous response term. The new model is:

    dH/dt = a * (T – T0) + b * dT/dt

    The first term, with parameter a, is the initial linear approximation of sea level’s exponential adjustment to a new equilibrium with a very long time constant. The second term is new, and represents fast processes. One interpretation of the “instantaneous” second term is as thermal expansion of the mixed ocean layer as it takes up heat.

    V&R find that the slow/fast model fits data and GCM simulations better. But the fit is a bit weird: the b parameter winds up negative, though one can interpret that as the net effect of a positive value with a delay. The resulting sea level projections are generally higher than Siddall et al. – 1.43m for A1FI.


    I’ll be taking a look at these new papers soon, with a few questions in mind:

    • Are the Rohling and Siddall equilibrium relationships comparable? (This is basically just a matter of overlaying the figures and adjusting for polar amplification.)
    • How well supported is the right tail of the nonlinear temp-sea level relationship in Siddall, and how does that matter to projections?
    • Is there a more physical dual-time-constant version of Vermeer and Rahmstorf that solves the negative-b problem?
    • Does the V&R dual model solve the problem of hindcasting inconsistency, identified by Grinsted?
  • Sea level update – Grinsted edition

    I’m waaayyy overdue for an update on sea level models.

    I’ve categorized my 6 previous posts on the Rahmstorf (2007) and Grinsted et al. models under sea level.

    I had some interesting correspondence last year with Aslak Grinsted.

    I agree with the ellipsis idea that you show in the figure on page IV. However, i conclude that if i use the paleo temperature reconstructions then the long response times are ‘eliminated’. You can sort of see why on this page: Fig2 here illustrates one problem with having a long response time:

    http://www.glaciology.net/Home/Miscellaneous-Debris/rahmstorf2007lackofrealism

    It seems it is very hard to make the turn at the end of the LIA with a large inertia.

    I disagree with your statement “this suggests to me that G’s confidence bounds, +/- 67 years on the Moberg variant and +/- 501 years on the Historical variant are most likely slices across the short dimension of a long ridge, and thus understate the true uncertainty of a and tau.”

    The inverse monte carlo method is designed not to “slice across” the distributions. I think the reason we get so different results is that your payoff function is very different from my likelihood function – as you also point out on page VI.

    Aslak is politely pointing out that I screwed up one aspect of the replication. We agree that the fit payoff surface is an ellipse (I think the technical I used was “banana-ridge”). However, my hypothesis about the inexplicably narrow confidence bounds in the Grinsted et al. paper was wrong. It turns out that the actual origin of the short time constant and narrow confidence bounds is a constraint that I neglected to implement. The constraint involves the observation that variations in sea level over the last two millenia have been small. That basically chops off most of the long-time-constant portion of the banana, leaving the portion described in the paper. I’ve confirmed this with a quick experiment.

    The multivariate random walk sensitivity analysis method is cool:

    The inverse monte carlo makes a uniform random walk in the model space, except that some steps are rejected according to some rules depending on the relative likelihood of the previous and current model. The end result is that it samples the model space according to the likelihood function. I.e. a region that has twice as high likelihood will be twice as densily sampled. The actual algorithm is extremely simple.

    Probability of accepting a given step in the random walk is

    rand*L(previous_accepted_model)<L(suggested_model)

    It is also called the metropolis algorithm. It is a very useful method for high dimensional model spaces, or model spaces with multiple minima. Klaus’ page has the derivations of why this works.

    The Metropolis algorithm is more famous for its use in simulated annealing. A few other notes:

    I also have some clarifications regarding the sea level record we used. We use the jevrejeva 2006 one from 1850 onwards. Prior to that we use the amsterdam record. Quote:
    We also extend the GSL reconstruction prior to 1850 using the record of annual mean sea level from Amsterdam since 1700 (van Veen, 1945) correcting it for the post glacial land submergence rate of 0.16 mm yr-1 (Peltier, 2004)

    You write: “Notice that during the period of disagreement, reported standard errors (in gray) are large. However, the magnitude of the discrepancy between series is larger than the reported standard error. Either the papers are measuring slightly different things, or there’s a significant systematic component that leads to underestimation of the error bounds.”
    My comment: It is to be expected that the two curves are more than a single standard error apart sometimes. These deviations may last for a long-long time considering that the uncertainty is highly serially correlated. In the G paper I model the uncertainty with something that is quite close to a markov chain process. the reason why we chose amsterdam prior to 1850 is because I think that the errors in the GIA correction for this location is rather low. Basically I think that the negative trend 1807-1850 in the jevrejeva06 curve is artificially caused by slightly wrong GIA corrections.

    On page VI you say: “It’s not clear to me how they handle the flip side of the problem, state estimation with correlated driving noise – I think they ignore that” – That is sort-of correct, in the sense that we treat the temperature as given (=error-free) in each of the experiments. But we do not ignore it: We address it by using different temperature reconstructions. So the true uncertainty should be gauged from all experiments.

    Aslak has some other interesting comments and papers:

  • Earthquakes != climate

    Daniel Sarewitz has a recent column in Nature (paywall, unfortunately). It contains some wisdom, but the overall drift conclusion is bonkers.

    First, the good stuff: Sarewitz rightly points out the folly of thinking that more climate science (like regional downscaling) will lead to action where existing science has failed to yield any. Similarly, he observes that good scientific information about the vulnerability of New Orleans didn’t lead to avoidance of catastrophe.

    For complex, long-term problems such as climate change or nuclear-waste disposal, the accuracy of predictions is often unknowable, uncertainties are difficult to characterize and people commonly disagree about the outcomes they desire and the means to achieve them. For such problems, the belief that improved scientific predictions will compel appropriate behaviour and lead to desired outcomes is false.

    Then things go off the rails.

    … perhaps the best thing that ever happened in the field of earthquake research was the recognition that earthquake prediction was likely to be impossible. In recent decades, the priorities of the US Geological Survey’s earthquake-hazard programme have moved away from prediction and towards the assessment, communication and reduction of vulnerabilities. This evolution has demanded closer collaboration between scientists and diverse regional and state decision-makers, to provide information that can help improve construction practices, land-use decisions, disaster-response plans and public awareness.

    This difficulty is on spectacular yet unacknowledged display in the climate-change arena. …. A central obstacle is that predictions of longterm doom have created a politics that demands immense costs to be borne in the near term, in return for highly uncertain benefits that accrue only in a dimly seen future.

    Science could help untangle this politically impossible dilemma by moving away from its obsession with predicting the long-term future of the climate to focus instead on the many opportunities for reducing present vulnerabilities to a broad range of today’s — and tomorrow’s — climate impacts. Such a change in focus would promise benefits to society in the short term and thus help transform climate politics. Strange as it may seem, the right lessons for the future of climate science come not from the success in predicting thunderstorms, floods and hurricanes, but from the failure to predict earthquakes.

    Earthquakes are a terrible analogy for climate, because their causes are strictly natural (except for small earthquakes from dams, mining, geothermal extraction, etc.). Therefore there’s no equivalent of emissions mitigation for earthquakes. Reducing vulnerability is a good idea, but Sarewitz is basically suggesting that we abandon consideration of the long term entirely, which is foolish, because climate is not entirely unpredictable.

    It’s also unjustified, because the dilemma he poses (“A central obstacle is that predictions of longterm doom have created a politics that demands immense costs to be borne in the near term, in return for highly uncertain benefits that accrue only in a dimly seen future”) is at least partially a false framing and in any case more a matter of economics than of science. Why not start by combining no-regrets mitigation with vulnerability reduction, rather than abandoning mitigation altogether?

    The proposed solution – focusing science on reducing vulnerability – also strikes me as misguided. To reduce vulnerability you don’t need much more science (especially if you believe that climate is fundamentally unpredictable). You need lots of economics and policy work. So, what to do with all those unemployed climatologists, now that we can ignore the long term climate? Turn them into Ag Economists?

    If climate is completely unpredictable, then we’d have to plan for vulnerability to a zero-mean forecast of future geophysical factors. For some localities and variables that might actually make sense – for example, here in Bozeman winter snowpack could go down (a temp effect) or up (a precip effect). But designing ports for sea level to rise or fall (both) would be rather expensive. Planning for vulnerability while pretending that we know nothing about anthropogenic effects on climate strikes me as a silly abdication of intelligence.

    Perhaps most importantly, there are surely some irreducible vulnerabilities to either geophysical surprises or knock-on effects of climate impacts like migration and war. You’d have to live a fatalist random worldview to plan for vulnerability yet fail to consider mitigation as a way of reducing your aggregate risk.

    A focus on vulnerability does have two benefits. First, we are committed to some climate change, so reducing vulnerability reductions have an intrinsic payoff. Presumably there are also win-wins, like getting rid of flood insurance subsidies on development in coastal areas that are also environmentally sensitive. Second, the act of planning for future climate variability may be a good way to make the implications of possible impacts, uncertainty, and long-lived infrastructure vulnerability very real to people.

  • The Health Care Death Spiral

    Paul Krugman documents an ongoing health care death spiral in California:

    Here’s the story: About 800,000 people in California who buy insurance on the individual market — as opposed to getting it through their employers — are covered by Anthem Blue Cross, a WellPoint subsidiary. These are the people who were recently told to expect dramatic rate increases, in some cases as high as 39 percent.

    Why the huge increase? It’s not profiteering, says WellPoint, which claims instead (without using the term) that it’s facing a classic insurance death spiral.

    Bear in mind that private health insurance only works if insurers can sell policies to both sick and healthy customers. If too many healthy people decide that they’d rather take their chances and remain uninsured, the risk pool deteriorates, forcing insurers to raise premiums. This, in turn, leads more healthy people to drop coverage, worsening the risk pool even further, and so on.

    A death spiral arises when a positive feedback loop runs as a vicious cycle. Another example is Andy Ford’s utility death spiral. The existence of the positive feedback leads to counter-intuitive policy prescriptions:

    But here’s the thing: suppose that we posit, provisionally, that the insurers aren’t the main villains in this story. Even so, California’s death spiral makes nonsense of all the main arguments against comprehensive health reform.

    For example, some claim that health costs would fall dramatically if only insurance companies were allowed to sell policies across state lines. But California is already a huge market, with much more insurance competition than in other states; unfortunately, insurers compete mainly by trying to excel in the art of denying coverage to those who need it most. And competition hasn’t averted a death spiral. So why would creating a national market make things better?

    More broadly, conservatives would have you believe that health insurance suffers from too much government interference. In fact, the real point of the push to allow interstate sales is that it would set off a race to the bottom, effectively eliminating state regulation. But California’s individual insurance market is already notable for its lack of regulation, certainly as compared with states like New York — yet the market is collapsing anyway.

    Finally, there have been calls for minimalist health reform that would ban discrimination on the basis of pre-existing conditions and stop there. It’s a popular idea, but as every health economist knows, it’s also nonsense. For a ban on medical discrimination would lead to higher premiums for the healthy, and would, therefore, cause more and bigger death spirals.

    What would work?

    By all means, let’s ban discrimination on the basis of medical history — but we also have to keep healthy people in the risk pool, which means requiring that people purchase insurance. This, in turn, requires substantial aid to lower-income Americans so that they can afford coverage.

    In other words: the positive feedback from selective participation in the risk pool makes insurance an all-or-nothing proposition. Either we go for all-out Darwinism around health and genetics (the de facto outcome of collapse) or require universal participation as Krugman suggests.

    Still, I can’t help wondering if there are alternatives that mitigate the self-selection problem while providing for a measure of individual choice. Is there a two-sided Vickrey auction that creates an incentive for everyone to reveal their true preference for health care over the long haul? Could such a system be made comprehensible and compatible with misperceptions of feedback, or would it just become a tax on ignorance?

  • Legislating Science

    The Utah House has declared that CO2 is harmless. The essence of the argument in HJR 12: temperature’s going down, climategate shows that scientists are nefarious twits, whose only interest is in riding the federal funding gravy train, and emissions controls hurt the poor. While it’s reassuring that global poverty is a big concern of Utah Republicans, the scientific observations are egregiously bad:

    29 WHEREAS, global temperatures have been level and declining in some areas over the
    30 past 12 years;
    31 WHEREAS, the “hockey stick” global warming assertion has been discredited and
    32 climate alarmists’ carbon dioxide-related global warming hypothesis is unable to account for
    33 the current downturn in global temperatures;
    34 WHEREAS, there is a statistically more direct correlation between twentieth century
    35 temperature rise and Chlorofluorocarbons (CFCs) in the atmosphere than CO2;
    36 WHEREAS, outlawed and largely phased out by 1978, in the year 2000 CFC’s began to
    37 decline at approximately the same time as global temperatures began to decline;

    49 WHEREAS, Earth’s climate is constantly changing with recent warming potentially an
    50 indication of a return to more normal temperatures following a prolonged cooling period from
    51 1250 to 1860 called the “Little Ice Age”;

    The list cherry-picks skeptic arguments that rely on a few papers (if that), nearly all thoroughly discredited. There are so many things wrong here that it’s not worth the electrons to refute them one by one. The quality of their argument calls to mind to the 1897 attempt in Indiana to legislate that pi = 3.2. It’s sad that this resolution’s supporters are too scientifically illiterate to notice, or too dishonest to care. There are real uncertainties about climate; it would be nice to see a legislative body really grapple with the hard questions, rather than chasing red herrings.

  • The Dynamics of Science

    First, check out SEED’s recent article, which asks, When it comes to scientific publishing and fame, the rich get richer and the poor get poorer. How can we break this feedback loop?

    For to all those who have, more will be given, and they will have an abundance; but from those who have nothing, even what they have will be taken away.
    —Matthew 25:29

    Author John Wilbanks proposes to use richer metrics to evaluate scientists, going beyond publications to consider data, code, etc. That’s a good idea per se, but it’s a static solution to a dynamic problem. It seems to me that it spreads around the effects of the positive feedback from publications->resources->publications a little more broadly, but doesn’t necessarily change the gain of the loop. A better solution, if meritocracy is the goal, might be greater use of blind evaluation and changes to allocation mechanisms themselves.

    Lamarckat35

    The reason we care about this is that we’d like science to progress as quickly as possible. That involves crafting a reward system with some positive feedback, but not so much that it easily locks in to suboptimal paths. That’s partly a matter of the individual researcher, but there’s a larger question: how to ensure that good theories out-compete bad ones?

    170px-Darwin_ape

    Now check out the work of John Sterman and Jason Wittenberg on Kuhnian scientific revolutions.