## Stabilization Wedges (Part 1)

Okay, let’s look at some plans for combating global warming! And let’s start with this paper:

• Stephen Pacala and Robert Socolow, Stabilization wedges: solving the climate problem for the next 50 years using current technologies, Science 305 (2004), 968-972.

I won’t try to summarize it all today, just a bit.

Stephen Pacala and Robert Socolow wrote this now-famous paper in 2004. Back then we were emitting about 6.2 gigatons of carbon per year, there were 375 ppm of carbon dioxide in the atmosphere, and many proposals to limit global warming urged that we keep the concentration below 500 ppm. Their paper outlined some strategies for keeping it below 500 ppm.

They estimated that to do this, it would be enough to hold emissions flat at 7 gigatons of carbon per year for 50 years, and then lower it to nothing. On the other hand, in a “business as usual” scenario, they estimate the emissions would ramp up to 14 gigatons per year by 2054. That’s 7 too many.

So, to keep emissions flat it would be enough to find 7 ways to reduce carbon emissions, each one of which ramps up linearly to the point of reducing carbon emissions by 1 gigaton/year in 2054. They called these stabilization wedges, because if you graph them, they look like wedges:

Their paper listed 15 possible stabilization wedges, each one with the potential to reduce carbon emissions by 1 gigaton/year by 2054. This is a nice way to start thinking about a very big problem, so many people have adopted it and modified it and criticized it in various ways, which I hope to discuss later. Right now I’ll only tell you about the original paper.

But before I even list any of their stabilization wedges, I should emphasize: stabilizing emissions at 7 gigatons is not enough to stay below 500 ppm forever! Carbon dioxide stays in the atmosphere a very long time. So, as Pacala and Socolow note:

Stabilization at any level requires that net emissions do not simply remain constant, but eventually drop to zero. For example, in one simple model that begins with the stabilization triangle but looks beyond 2054, 500-ppm stabilization is achieved by 50 years of flat emissions, followed by a linear decline of about two-thirds in the following 50 years, and a very slow decline thereafter that matches the declining ocean sink. To develop the revolutionary technologies required for such large emissions reductions in the second half of the century, enhanced research and development would have to begin immediately.

What’s the “declining ocean sink”? Right now the ocean is absorbing a lot of CO2, temporarily saving us from the full brunt of our carbon emissions — while coral reefs, shellfish and certain forms of plankton suffer from increased acidity. But this won’t go on forever; the ocean has limited capacity.

Pacala and Socolow consider several categories of climate wedges:

• efficiency and conservation
• shifting from coal to gas
• carbon capture and storage
• nuclear fission
• renewable energy sources
• forests and agriculture

Today let me just go through the first category. Here they list four wedges:

1. Efficient vehicles: increase the fuel economy for 2 billion cars from 30 to 60 miles per gallon. Or, for those of you who don’t have the incredible good luck of living in the USA: increasing it from 13 to 26 kilometers per liter. When they wrote their paper, there were 500 million cars on the planet. They expected that by 2054 this number would quadruple. When they wrote their paper, average fuel efficiency was 13 kilometers/liter. To achieve this wedge, we’d need that to double.

2. Reduced use of vehicles: decrease car travel for 2 billion 30-mpg cars from 10,000 to 5000 miles per year. In other words: decreasing the average travel from 16,000 to 8000 kilometers per year. (Clearly this wedge and the previous one are not additive: if we do them both, we don’t save 2 gigatons of carbon per year.)

3. Efficient buildings: cut carbon emissions by one-fourth in buildings and appliances. This could be done by following “known and established approaches” to energy efficient space heating and cooling, water heating, lighting, and refrigeration. Half the potential savings are in the buildings in developing countries.

4. Efficient coal plants: raise the efficiency of coal power plants to 60%. In 2004, when they wrote their paper, “coal plants, operating on average at 32% efficiency, produced about one fourth of all carbon emissions: 1.7 GtC/year out of 6.2 GtC/year.” They expected coal power plants to double their output by 2054. To achieve this wedge, we’d need their average efficiency to reach 60%.

There are lot of questions to ask! Which do you think are the most easily achieved of these wedges? What are the biggest problems with their reasoning so far? And so on…

I would love any interesting information you have on: 1) ways to make vehicles more efficient, 2) ways to coax people to drive less, 3) ways to make buildings more efficient, and 4) ways to make coal power plants more efficient. Please post it here, with references if you can!

I’ll conclude for now with a couple of tiny points. First, they seem to vacillate a bit between saying there were 6.2 and 7 gigatons of carbon emitted in 2004, which is a bit odd, but perhaps just a way of giving the world a bit of slack before levelling off emissions at 7 GtC/year. I guess it’s not really a big deal.

Second, they aren’t idiots: despite the above graph, they don’t really think carbon emissions will increase linearly in a business-as-usual scenario. This is just a deliberate simplification on their part. They also show this supposedly more accurate graph:

They say the top curve is “a representative business as usual emissions path” for global carbon emissions in the form of CO2 from fossil fuel combustion and cement manufacture, assuming 1.5% per year growth starting from 7.0 GtC/year in 2004. Note this ignores carbon emissions from deforestation, other greenhouse gases, etc. This curve is growing exponentially, not linearly.

Similarly, the bottom curve isn’t flat: it slopes down. They say the bottom curve is a “CO2 emissions path consistent with atmospheric CO2 stabilization at 500 ppm by 2125 akin to the Wigley, Richels, and Edmonds (WRE) family of stabilization curves described in [11], modified as described in Section 1 of the SOM text.”

Here reference [11] is:

• T. M. L. Wigley, in The Carbon Cycle, eds. T. M. L. Wigley and D. S. Schimel, Cambridge U. Press, Cambridge, 2000, pp. 258–276.

and the “SOM text” is the supporting online material for their paper, which unfortunately doesn’t seem to be available for free.

### 78 Responses to Stabilization Wedges (Part 1)

1. Curtis Faith says:

If you want to end global warming then we need to work together to fight for equality first. The governments are controlled by money. Only when we end oppression will there be enough power to make the changes needed to turn global warming around.

You can help change the world. You lead a tribe of scientists and mathematicians.

The solution will not come from a more strenuous application of approaches that have demonstrated their failure time and time again. We must try something different.

Something like this: http://bit.ly/dj8Xmf

• John Baez says:

I wish I led a tribe of scientists and mathematicians. Or maybe I do — but if so, it’s a tribe that doesn’t care what the chief wants. When I switched from n-categories to something potentially useful, practically nobody followed along.

The solution will not come from a more strenuous application of approaches that have demonstrated their failure time and time again.

Like calling for an ‘end of oppression’?

• Frederik De Roo says:

perhaps it was a band of scientists rather than a tribe ;-)

• John Baez says:

Yeah — and it’s a band where everyone plays their own tune.

• Todd Trimble says:

Trying to guilt-trip us there, John?

Let me say that $n$-categories are useful in the way that all math is useful.

Also let me say that the amount of things one has to learn to help ‘save the planet’ is quite staggering. It’s a lot of time out of the day to try to keep up. It’s not quite that your fans “don’t care”!

• John Baez says:

Todd wrote:

Trying to guilt-trip us there, John?

Not really — I didn’t think “us” was listening.

Let me say that $n$-categories are useful in the way that all math is useful.

Oh, I agree absolutely! They are among my favorite parts of mathematics, and I wasn’t trying to diss ’em.

When I began seriously trying to work on environmental issues, my mother said “it must feel good that now you’re doing something useful”. This was rather galling — but also amusing, so now I half-jokingly call this work my attempt to do something useful for a change.

After a lifetime spent on pure math and abstruse theoretical physics, the change is a bit tough, not least because it seems to involve leaving behind most of my friends… at least in some sense of the term ‘leaving behind’. I still like them, but I’m not seeing them at conferences anymore, not seeing their comments on my blog articles, not spending much time commenting on theirs, not eagerly trying to work together on problems, etc.

Also let me say that the amount of things one has to learn to help ‘save the planet’ is quite staggering. It’s a lot of time out of the day to try to keep up. It’s not quite that your fans “don’t care”!

I can’t tell who is ‘trying to keep up’, apart from people who are posting comments here. So I assumed that most of the mathematicians I know weren’t reading this blog anymore. But maybe I’m wrong.

If anyone else out there is trying to keep up, I’d love to get questions or comments on this blog.

I’m trying to learn a lot of stuff here on the blog, and then explain it in a more organized way on the Azimuth Project. That’s supposed to eventually make it easier for people to learn this stuff. But I expect that most people will focus more energy on a few specific topics — that would be sensible, anyway. So I don’t think the amount of stuff one has to learn is quite so staggering.

It would be unfortunate if my dilettantish wandering through a wide range of subjects made anyone think they needed to be an expert on all these subjects before they could do anything useful to help the environment.

• Tim van Beek says:

Todd said:

Also let me say that the amount of things one has to learn to help ‘save the planet’ is quite staggering.

John responded:

I don’t think the amount of stuff one has to learn is quite so staggering.

Todd’s got a point there: even to read all Azimuth blog posts and the first level of the link tree (all resources that are directly linked to a blog post), plus a fair fraction of the books listed on the recommended reading page on Azimuth (which I haven’t done yet, by the way), requires a serious amount of time.

Of course we

…expect that most people will focus more energy on a few specific topics — that would be sensible, anyway.

…but the entrance barrier seems to be high, and you know the Kramers rate: It decreases exponentially with the height of the potential barrier…

• John Baez says:

Tim wrote:

Todd’s got a point there: even to read all Azimuth blog posts and the first level of the link tree (all resources that are directly linked to a blog post), plus a fair fraction of the books listed on the recommended reading page on Azimuth (which I haven’t done yet, by the way), requires a serious amount of time.

Of course global warming and other environmental problems will not be solved merely by people sitting around reading blog entries and links. It’s good for people to become well-informed on these issues, but it’s bad for people to think of all this reading as a ‘barrier’ to be ‘overcome’ before they can do anything useful.

After all, suppose you read all this stuff: then what?

On my part, I need to shift the focus to what people can do. This will naturally tend to happen as I figure out more about what I want to do, and talk about that. Right now I’m just trying to get a sense of the overall landscape.

The interviews with people on This Week’s Finds are also supposed to provide ‘role models’, illustrating different things that people can do. Perhaps Nathan was too intimidatingly well-informed to be a plausible role model for most of us, but I’ll eventually get around to some normal mortals.

Of course, it’s the youngsters I really want to reach: the people who haven’t settled on a career yet. Once upon a time, some of them read This Week’s Finds in Mathematical Physics and decided that loop quantum gravity or n-categories were cool things to work on. (I believe one of them was Nathan.) Now I’m hoping to show them that environmental issues are just as cool.

• Nathan Urban says:

Yes, it was “This Weeks Finds” that inspired me to study quantum gravity. Unfortunatey, I think it is harder to capture “mindshare” now. Usenet was a fairly focused venue with a number of aspiring physicists. There was just one place to discuss it. On the Web, there are too many alternatives, and no clear way of finding them. Individual blogs can get lost in the crowd.

On the other hand, there are few climate blogs attempting to target young scientists with semitechnical material, and a lot of potential interest. I suppose it’s a matter of advertising.

I agree that people shouldn’t have to feel they have to master everything out there in order to contribute. On the other hand, I think people here don’t have a clear idea of what it is they want to do. With a clear goal in mind, it’s easier to focus on relevant details rather than getting lost in an ocean of material. (I remember once wanting to learn a little bit about all the different renormalization techniques out there, and John advising me to just start by picking one and concentrating on that.)

Speaking as someone who decided to try to contribute to a new field, it’s really kind of like being in grad school again. There’s so much out there, and without an “advisor” to help focus one’s interests, it’s easy to get overwhelmed.

• Curtis Faith says:

Yes, exactly.

2. Tim van Beek says:

1. Efficient vehicles…

This is the easiest, we have known how to build 3-litre-cars (3 liter gasoline per 100 kilometers) for at least a decade now (I think even longer). Increase the price of gasoline and subsidize cars with a low consumption, car companies will figure out how to build attractive and useful 3-litre-cars en masse.

• John Baez says:

There’s a fairly high tax on gasoline in Germany, right? But not high enough to make companies build 3-liter cars? Does anyone have a good estimate of what gasoline price would be needed?

• Tim van Beek says:

Good question…yes, there is a high tax on gasoline, in addition you don’t have to pay any motor vehicle tax if you have a 3-litre-car.

The German Wikipedia has a fairly long article about this: Niedrigenergiefahrzeug, including a discussion why these cars did not have much success yet (is there a translation in English for “Niedrigenergiefahrzeug”? Low energy vehicle?).

IMHO the most important reason is that cars are still the most important status symbol, there is no better way to show how important you are than to drive a premium car (“Germans spend more time caring for their car than caring for their body”).

• Tim van Beek says:

You know, there is a running gag: “he’s driving a XY premium car with built in ROW (right of way)”.

• grlcowan says:

In saying Germany’s gasoline taxes are not high enough to make companies build 3-L cars, you are obscuring the fact that the companies’ reticence stems from motorists’ reticence to buy.

Now, why won’t motorists buy perfectly practical small cars? Because they are low-status, as some previous commentators mention.

What makes them low-status? I think government attitudes have a lot to do with it. Governments allow the well-to-do to drive big cars fast, even if they are over 60 or under 25. That means not just status, but personal safety, has to be on the minds of practical motorists sharing public roads with them.

In light of that, perhaps your final question can be rephrased this way: how high must we raise the amount of money government makes, per unit gasoline, to discourage it from promoting gasoline consumption?

That rephrasing is wrong, of course, if you had some beneficiary other than government in mind for the extra gasoline revenues gained by increasing the price motorists pay. Dr. James Hansen recommends all such revenues be divided out equally to the citizens, so that the fraction of society that consumes more fossil fuel than the average transfers a little money to the fraction that consumes less than the average.

But if you did indeed mean government would get more money, well, it’s like asking, how many times must one feed the cat things he likes to get him to stop asking.

• John Baez says:

grlcowan wrote:

In saying Germany’s gasoline taxes are not high enough to make companies build 3-L cars, you are obscuring the fact that the companies’ reticence stems from motorists’ reticence to buy.

Since you were replying to my comment, I might guess the word “you” here meant me. But I didn’t say Germany’s gasoline taxes are not high enough to make companies build 3-L cars. I was only asking Tim some questions. So maybe “you” meant Tim?

(To avoid such confusion, I refer to people by their names when engaged in big conversations like this.)

Now, why won’t motorists buy perfectly practical small cars? Because they are low-status, as some previous commentators mention.

That could be true. When I drive the highways of Los Angeles and see people aggressively driving oversized SUVs, I get the impression that some people are using their cars primarily as a form of self-expression — a kind of substitute for the body. As they drive more and walk less, they get fatter and need bigger cars:

And as crowds of big SUVs with one passenger each congeal in massive traffic jams, I start thinking that this culture deserves to die. I’m not saying I really want it to see it die — I guess that’s just my own personal form of road rage. I’d rather see it transform.

• streamfortyseven says:

It’s interesting that you’re still talking about cars for long-haul (>20km) transport when it’s well-established that trains are far more energy-efficient, to a factor of 10 or more.
See the Wikipedia article Fuel efficiency in transportation:

Summary:
Autos-
2008 Volkswagen Polo:         0.2584 kWh/passenger-km
2008 Honda Insight:             0.3332 kWh/passenger-km
2008 Honda Civic Hybrid:      0.3536 kWh/passenger-km
2008 Toyota Prius:              0.3468 kWh/passenger-km
2008 GM EV1:                    0.1768 kWh/passenger-km

Trains-
Combino light rail:                 0.0236 kWh/passenger-km
East Japan Railway:              0.0973 kWh/passenger-km
TGV-1997 EC study:              0.0470 kWh/passenger-km

• DavidTweed says:

That’s an interesting table. It would be a useful reference on a page in the wiki. (Ok, subtlety in hints isn’t my strong point.)

• Tim van Beek says:

Of course there is a lot of potential for public transportation, and especially for trains, in the USA :-)

But Japan and Europe already have a well developed system of public transportation, including high speed trains (ICE in Germany, TGV in France, see e.g. high speed trains).

As one can learn from Japan and Europe, there are limits to the extent that public transportation can reduce the use of cars. Therefore I think that wedge 2 is the most unrealistic one.

• Giampiero Campa says:

For electric cars and hybrids to come to the rescue, battery technology (which has already advanced considerably), has to keep on improving. I am not sure that this actually can be done, since the level of energy density for batteries is already impressive.

However we can always hope:
http://www.allcarselectric.com/blog/1050863_electric-car-drives-375-miles-at-55-mph-recharges-in-6-minutes

• phorgyphynance says:

Better yet:

http://www.teslamotors.com/

• streamfortyseven says:

Tesla motors prices: Roadster base price \$101,500.00
S2, available 2012. \$56,500.00

• streamfortyseven says:

That’s a proof-of-concept car, not a stock car, but stripped down. Most production electric cars are prohibitively expensive, in the range of \$60,000 to \$100,000, and you won’t make up the savings in gas money with the extra amount you spend on the car until you’ve had the car for ten years – and if you have to replace the batteries, even longer.

• Tim van Beek says:

Several big players in the car industry prepare for mass production of electric cars, but unfortunately I don’t have any good estimates on the cost per unit of those. My educated guess is somewhere between 20 000 and 30 000 Euros.

3. Frederik De Roo says:

> coal plants, operating on average at 32% efficiency

isn’t 1/3 efficiency generic for thermal production of electricity?

• Frederik De Roo says:

I checked – luckily this appears not exactly the case.

(from the Wikipedia article Thermal power station)

The energy efficiency of a conventional thermal power station, considered as saleable energy (in MWe) produced at the plant busbars as a percent of the heating value of the fuel consumed, is typically 33% to 48% efficient. This efficiency is limited as all heat engines are governed by the laws of thermodynamics (See: Carnot cycle).

Current nuclear power plants operate below the temperatures and pressures that coal-fired plants do. This limits their thermodynamic efficiency to on the order of 30–32%.

There are some figures here (but I would like to find more details): Efficiency of thermal electricity generation.

This isn’t reassuring, though:

The positive impacts on the environment (particularly decreased emissions) from the efficiency improvement in the electricity production, may be offset by the fast increase in electricity consumption, which is growing at an average rate of 1.7 % per year since 1990 (see ENER 18), especially considering that over half of this electricity (55.4 % in 2007) is produced from coal, gas and oil (see ENER 27) .

• John Baez says:

Frederik wrote:

The energy efficiency of a conventional thermal power station, considered as saleable energy (in MWe) produced at the plant busbars as a percent of the heating value of the fuel consumed, is typically 33% to 48% efficient.

Pacala and Socolow suggest raising the efficiency of coal power plants to 60%. Is this thermodynamically possible or not? If it is, is it actually feasible?

• Frederik De Roo says:

I haven’t found thermodynamic arguments yet, but at least Pacala and Socolov are not the only ones that mention this number, see e.g. Vision 21 . Unfortunately, they don’t provide further details.

• John Baez says:

You can easily use the formula for the efficiency of the Carnot cycle to put a lower bound on the temperature you’d have to burn coal at to get 60% efficiency if it’s transferring heat to room-temperature water, or boiling water. But that bound is overoptimistic for any known technology.

• Frederik De Roo says:

First of all there is the theoretical Carnot cycle, and on Thermal efficiency, wikipedia:

Power plants: Rankine cycle The Rankine cycle is the cycle used in steam turbine power plants. The overwhelming majority of the world’s electric power is produced with this cycle. Since the cycle’s working fluid, water, changes from liquid to vapor and back during the cycle, their efficiencies depend on the thermodynamic properties of water. The thermal efficiency of modern steam turbine plants with reheat cycles can reach 47%, and in combined cycle plants it can approach 60%.

Gas turbines: Brayton cycle The Brayton cycle is the cycle used in gas turbines and jet engines. It consists of a compressor turbine that increases pressure of the incoming air, then fuel is continuously added to the flow and burned, and the hot exhaust gasses are expanded in a turbine. The efficiency depends largely on the ratio of the pressure inside the combustion chamber p2 to the pressure outside p1.

For the 60% they refer to the GE H system

• John Baez says:

Great! While it’s still fresh in your mind, can I lure you into putting this information, with links, on a relevant Azimuth Project page? Perhaps the page on Stabilization wedges, for now. Someday we’ll have a page on coal-fired power plants, but right now I’m planning to go through all 15 of Pacala and Socolow’s wedges and add comments and criticisms. I haven’t done it yet, but you can start if you want.

4. John F says:

The answer isn’t consumer marketing; Popeye had less of an effect on spinach consumption than Wimpy did on hamburgers (both consistent with zero). Although I have no idea how fashion actually works, I do not believe that Paris Hilton or anybody could be an effective pusher of three wheel plastic vehicles, nor Justin Bieber a poster child for public transportation. Consumer information has also demonstrably failed miserably. The only answer is regulation.

• DavidTweed says:

I think Tim is talking about 100km per 3l of fuel cars, not 3 wheel cars. I don’t imagine that 3 wheels rather than 4 change fuel efficiency noticeably — the very small number of 3 wheel cars in the UK in the 1970s (Reliant Robin’s) were due to a tax dodge because in the tax legislation a “car” was legally defined as a 4 wheel vehicle, not because you’d actually choose 3 wheels for any technical reason.

Maybe if Appple can be persuaded that the future lies in lending their branding to an “iPodule”… :-)

• John F says:

My use of 3 wheelers was shorthand for deliberately downsized design. However they are fun too.
http://www.nitrobahn.com/featured/top-10-three-wheel-concept-vehicles/
Anyway if you start with four large tires, needed assuming you’re going to be going at least 100 kph, then add a hefty frame, then you need a hefty power source, room to carry it and you and etc. You’re back to the typical automobile, which means it’s internal combustion. Nobody wants to be limited to driving a typical automobile only 30 km or else drag along a ton of batteries.
Everyone has to give up individual speed to gain efficiency. I’d personally be happy with a nice cheap electric tricycle at 20 kph for local trips, and easy access good public trains for the rest.
There aren’t any environmentally friendly options for a five member family to take long Sunday drives in the same vehicle.

5. umass1993 says:

This is the first sentence of http://en.wikipedia.org/wiki/Jevons_paradox :

“In economics, the Jevons paradox, sometimes called the Jevons effect, is the proposition that technological progress that increases the efficiency with which a resource is used tends to increase (rather than decrease) the rate of consumption of that resource.”

This principle was discovered in the 19th century. Evidently, Socolow and Pacala aren’t current in their resource economics theory.

I am wondering why other people on this site are not aware of this.

• DavidTweed says:

I think an awful lot of people are aware of this: for example, John Baez mentioned it in the context of the Singapore speech as “the rebound effect”.

It’s also important to note (as indicated by the rest of the wiki page) that the Jevons effect only refers to increasing efficiency on its own. In principle, genuinely convincing people that they need to take actions to reduce carbon dioxide emissions along with increasing efficiency would work. The difficulty is figuring out ways to genuinely convince them.

• streamfortyseven says:

The best way to convince people not to do an activity is to tax it; the way that this could be done at the state level is to measure CO2 emissions on a dynamometer, along with nitric oxides and the like, and assess a tax accordingly. Make the tax high enough, and you create an incentive to get cars with high CO2 emissions off the road.

• Elsewhere, John Baez says,

And as crowds of big SUVs with one passenger each congeal in massive traffic jams, I start thinking that this culture deserves to die.

and here, ‘streamfortyseven’ says,

The best way to convince people not to do an activity is to tax it …

It’s also the best way to persuade civil servants to think of ways to make them continue doing it while they, the civil servants, are arriving at work; while leaving; and at all times in between.

Baez’s revulsion is to a state of affairs that, to many on public stipends, is absolutely circled-thumb-and-forefinger A-OK. Perhaps the mouth tells a different story, but if so, believe the hand.

So the equal-dividend Hansen scheme I mentioned is, I think, key.

• John Baez says:

umass1993 wrote:

“In economics, the Jevons paradox, sometimes called the Jevons effect, is the proposition that technological progress that increases the efficiency with which a resource is used tends to increase (rather than decrease) the rate of consumption of that resource.”

This principle was discovered in the 19th century. Evidently, Socolow and Pacala aren’t current in their resource economics theory.

I am wondering why other people on this site are not aware of this.

I’m aware of the ‘Jevons effect’, and I think a bunch of other people here are too: whenever someone here mentions improving efficiency, someone else mentions this effect. But thanks for pointing out this important criticism of Socolow and Pacala’s item 1.

It seems very plausible that the ‘Jevons effect’ is real: it’s a consequence of elasticity of demand. So the question becomes: what’s the precise extent that this effect negates conservation through increased efficiency. If my car mileage doubles, will I drive twice as much, or only 1.5 times as much? If I buy compact fluorescent light bulbs that achieve the same luminosity with half the wattage, will I use twice as much light in my house? I doubt it.

I think these questions can only be answered with a lot of empirical research. But economists spend a lot of time trying to estimate the elasticity of demand for various goods, so presumably a lot of this research has already been done. It needs to be taken into account in any detailed plan of action.

• umass1993 says:

“I think these questions can only be answered with a lot of empirical research.”

Not tough to do. Just look at electricity consumption in the US over the past forty years … a time of rapid increases in appliance efficiency. Consumption increased every year until an aprupt rise in prices over the past five years.

here is a consumption graph:
http://www.eia.doe.gov/emeu/aer/pdf/pages/sec8_6.pdf

here is a price graph:
http://www.eia.doe.gov/emeu/aer/pdf/pages/sec8_38.pdf

“But thanks for pointing out this important criticism of Socolow and Pacala’s item 1. ”

And item 3, and item 4. Even item number 2 is suspect, because if people drive less miles then more oil will be available for jet fuel and industrial use.

This is why, in my mind, wishful thinking is the single greatest obstacle to tackling global climate change.

• John Baez says:

umass1993 wrote:

Not tough to do. Just look at electricity consumption in the US over the past forty years … a time of rapid increases in appliance efficiency. Consumption increased every year until an abrupt rise in prices over the past five years.

Studying the Jevons effect actually is rather tough. For example, to prove the Jevons effect occurs for consumption of electrical power, you’d have to get evidence that the rise in electricity consumption in the last 40 years was (in part) caused by increases in efficiency. There are plausible other explanations: for example, more people treating a wider range of electrical appliances as ‘necessities’.

40 years ago, a typical American household might have a radio, a television, a refrigerator, a dishwasher and a clothes washer and drier, together with lightbulbs and (rarely) an electrical furnace. Now there’s a vastly larger range of electrical appliances, and it’s common to have several televisions. Some of this is due to the invention of new gadgets, while some is related to the drop in (inflation-adjusted) prices of these gadgets. I have no idea what fraction is due to the increases in electrical power efficiency of these gadgets, but I wouldn’t be surprised if that played a rather small part.

… wishful thinking is the single greatest obstacle to tackling global climate change.

I think that’s true in many many ways, ranging from ‘climate change isn’t real’ to ‘we’re not causing it’ to ‘we can solve it by just doing X’.

You’re right that the Jevons effect might also impact the other items on Pacala and Socolow’s list. I thought of that while walking to work, edited my comment to include those, then saw you’d already mentioned it and re-edited my comment to remove that change.

I plan to put these critiques into the relevant Azimuth Project page: Stabilization wedges.

• Tim van Beek says:

John said:

Studying the Jevons effect actually is rather tough.

That’s true for “multidimensional” effects like this one:

…if people drive less miles then more oil will be available for jet fuel and industrial use.

It’s much easier to do for a simple one dimensional problem: The safety of cars has increased significantly over the last decades, yet the number of traffic deaths has stalled or decreased only slightly (again, I only know the numbers relevant to Germany, but I guess you all know the relevant statistics for your own countries :-). I’ve read about studies showing that this is at least partially due to a more reckless driving style, for example people drive much faster when streets are wet, because they trust the antiblocking system.

• John Baez says:

Tim wrote:

The safety of cars has increased significantly over the last decades, yet the number of traffic deaths has stalled or decreased only slightly.

I guess you could use these statistics to estimate what people consider an acceptable risk of dying in a traffic accident. You make cars safer, and they drive more recklessly to bring the risk back up to this level. One can only hope that natural selection does its thing over time.

Sorry, but sometimes I despair at the human race, and this is the second time in this thread. I guess the subject of cars does it to me…

• Tim van Beek says:

John wrote:

I guess you could use these statistics to estimate what people consider an acceptable risk of dying in a traffic accident. You make cars safer, and they drive more recklessly to bring the risk back up to this level.

Yes, that’s true. With modern electronic safety systems, you won’t experience any sideslip anymore, which leads to a dangerous illusion of control.

There is a similar psychological effect with regard to recycling and energy consumption: Studies show that people who are proud to live in an ecologically sustainable way (alright, I’m talking about studies about the core of the German green party, but I’m sure the psychology applies to everyone) first generate some good conscience by recycling their usual consumer waste, then don’t take care of oil that gets into the ground when they wash their car… It’s a trade mechanism that is behind the Jevons paradox: Ok nature, I did something for you, now cut me some slack :-)

6. umass1993 says:

All you are doing is explaining how higher efficiency leads to greater consumption. This is always true. for example, if corn is cheap to make, people will consume more corn, perhaps in the form of corn syrup, or perhaps in the form of biofuels or whatever.

Corn, cars or computers, etc. this is always true.

In short, price determines demand. This is high school economics. The notion that the economics of energy should be different is a sham.

At the heart of the “efficiency fix” is the rudimentary logical fallacy of thinking that just because higher price leads to higher efficiency and lower demand, then higher efficiency should lead to lower demand.

• DavidTweed says:

It would certainly be a fallacy to say that

At the heart of the “efficiency fix” is the rudimentary logical fallacy of thinking that just because higher price leads to higher efficiency and lower demand, then higher efficiency should lead to lower demand.

The thing is, I don’t think anyone is actually saying that. To pick an analogy, in the UK (until recently) the price of pork sausages was decreasing over time, but that didn’t result in Muslims increasing their consumption of pork sausages, because they have other factors affecting their mental processes (in this case, a religious prohibition from eating pork) as well as marginal utility economics.

The various proposals all seem to be combining some other mechanism (taxing carbon dioxide emissions, convincing people they should reduce CO2, etc) along with increasing efficiency. (I can’t read the paper at the moment, but Socolow and Pacala explicitly mention in the paper that they’re not considering the price implications that need to go along with their proposals.) I don’t think setting up these parallel incentives in addition to efficiency is going to be easy, or even understood yet, but it’s part of the picture.

• John Baez says:

umass1993 wrote:

All you are doing is explaining how higher efficiency leads to greater consumption.

When mentioning people here, I suggest avoiding the word “you” unless your comment appears directly under the comment you’re replying to. I can’t tell who “you” is supposed to be here, since your comment appears on its own in the comment tree, underneath various statements by John Baez, David Tweed, Tim van Beek and others, but not directly replying to any one of these.

One way to avoid this confusion is to start with a quick quote of the person you’re referring to, as I just did here. Here’s what I wrote in HTML:

umass1993 wrote:

<blockquote>
All you are doing is explaining how higher efficiency leads to greater consumption.
</blockquote>

• Tim van Beek says:

umass1993 wrote

In short, price determines demand. This is high school economics.

Sure, the fun starts when one compares the high school economics (or freshman economics) to reality.

One example: People are willing to pay more for eggs that do not come from mass farming. The supermarket around the corner where I live has eggs from mass farming and eggs from happy chickens living on local farms for twice the price, people buy the latter. There is no difference in taste etc. Actually the hard part of the story was to convince the supermarkets to even offer the more expensive ones, because at first they did not believe at first that anyone would buy those.

Now the Jevons paradox points out that this anti price-demand trend may fail to work out and is therefore a second order correction to high school economics :-)

You yourself already mentioned a second example: Computers. The computer market suffers from a severe and enduring deflation, but continues to boom and has so for at least the past 20 years. (If you know about an economist who has a good theory explaining this, I’d like to know).

• Frederik De Roo says:

I’m sorry to go so far off topic (it has nothing to do with stabilization wedges, so delete if unappropriate) but I don’t agree there is no difference with respect to the egg: I have often remarked a difference in shell strength between cheap and expensive eggs.

7. jack fuller says:

One of the more absorbing books I have come across lately is “Ratification”, by MIT history professor Pauline Maier. She is apparently one of the first to attempt a narrative history of the ratification of the U.S. Constitution by the colonies. I thought I had a fairly good appreciation of the discussions and debates involved in adopting the constitution, but this book was quite revelational. Opinions and feelings were much more divergent on almost every element of that document than I had for some reason realized.

Patrick Henry and James Madison were bitterly on opposite sides, as were various others of the founders, which point struck me that in affairs of the body politic, men (and now women) can totally disagree on almost anything and for almost any reason! And, indeed, each side didn’t hesitate to accuse the other of all manner and level of bad judgment and/or incompetence — quite the case in some instances, and plainly not in others.

Some history is apparently constrained to be repeated, albeit the study of history can at least furnish perspective about the inevitable human condition. In regard to the disputations regarding climate change, the above work actually provided me just a little more calm and insight into the realities of politics.

• John Baez says:

Yes, it is encouraging to see that people have succeeded in solving problems that at the time must have seemed nearly impossible.

The engineer Saul Griffith said that tackling climate change is “is not like the Manhattan Project, it’s like the whole of World War II, only with all the antagonists on the same side this time.”

In terms of the scale of the problem that’s true. But of course it’s not like World War II — because we’re not battling other people, we’re battling our own bad habits, and a lot of us still don’t think there’s any need.

So these historical analogies only go so far — but still, that sounds like an interesting book!

8. 300 kWh batteries would weigh many too many tons, so you didn’t mean that. 300 kW is also way overkill and only needed for speed.

Right and right. I meant specially developed internal boron combustion engines plus nuclear B2O3 dissociation plants to supply them.

They’re hard to develop, and if they depend on on-board air oxygen extractors, the first iterations are likely to be woefully inefficient. Maybe 20 percent, pellet-bin-to-wheel.

As such, they will totally own motorists’ aspirational mindshare, to coin a phrase … maybe it’s better just to say, as soon as they are visible and tangible, everyone will want one. All that are made will be bought.

After the 300 driveshaft kWh has, at the supposed 20 percent efficiency, been had, there are 318 kg of B2O3 in the ash section of the bicameral fuel/ash bin.

John F. mentioned the Tesla’s 450-kg battery. The Tesla is a nice little thing, but this 318-kg B2O3 load has done the work of a 29-gallon gas tank. That’s SUV territory, the territory of cars that could make a sheet-metal backdrop to the Toyota that is, itself, the sheet-metal backdrop in my montage.

Maybe, when City Hall* ceases to be so happy about the subsidy it gets from SUV drivers, it will find ways of ending the cars’ popularity. But if it turns out the common motorist was easily led into liking them and is hard to lead away, we can continue to disapprove of his choice but get him to make it clean.

* By “City Hall” I mean all levels of government collectively

9. […] Last time we covered four wedges related to energy conservation and increased efficiency. Wedge 5 is in a category of its own: […]

10. Will Robertson says:

How are the first two wedges not additive? If the first wedge halves some measure of carbon emissions (improving fuel economy) and the second wedge halves it again (driving less), I don’t see how you’re implying they cancel each other out.

Oh, that’s not what you’re saying—simply that they don’t both affect the carbon output linearly when combined together. But the phrasing is ambiguous, because it seems possible (from the information provided here) that the two wedges *could* save 2 gigatons per year.

• John Baez says:

Will wrote:

Oh, that’s not what you’re saying—simply that they don’t both affect the carbon output linearly when combined together.

Right. I’m a mathematician, so it’s “additive” when 1 and 1 make 2. But in this case they don’t.

In wedge 1, they say increasing the fuel economy of all the cars in the world from 30 to 60 miles per gallon could save us 1 gigaton of carbon per year by 2054. In wedge 2, they say that decreasing travel for all the cars in the world from 10,000 to 5000 miles per year would save us 1 gigaton of carbon by 2054. I was just noting that if we do both those things, we wouldn’t save 2 gigatons of carbon.

Each measure by itself halves the carbon emissions caused by cars — so doing them both would multiply those emissions by 1/4. If halving the emissions saves 1 gigaton/year, that means that before we halved them, we’d be using 2 gigatons/year. So, if we succeed in multiply auto emissions by 1/4, cars will be putting out 1/2 a gigaton per year. So, doing both measures will save 1.5 gigatons/year.

So, in this case 1 and 1 would only make 1.5.

According to their figures, to save 2 gigatons of carbon per year by reducing auto emissions, we’d have to eliminate auto emissions completely!

Maybe some of my wording was ambiguous, but I hope this is clear.

• Will Robertson says:

Perfectly sensible — I suspected your clarification is what you meant but I just wanted to make sure. Do you have any idea whether auto emissions are indeed responsible for 2 gigatons of carbon per year?

(Unrelated tangent: I have a bit of a pet peeve that lots of climate change talk refers to absolute amounts of carbon (or some amount of carbon per year) but unless you’re very familiar with the topic (and I’m unfortunately not) it’s hard to put things in perspective.)

• Frederik De Roo says:

The way I understood wedge 1 and wedge 2 is that they assume there will be four times more cars in 2054 (bringing the total to 2 billion). So to keep emissions flat, cars have to become twice as efficient and should travel half as far. The amount of carbon emissions depends on the number of cars, and this is an uncertainty. I haven’t checked it but I guess it could be looked up (or calculated) relatively easily. It’s just the fuel burnt that is emitted into the air.

If wedge 1 and 2 are not chosen, the additional emissions of cars should be countered by other wedges. But simplistically, one could think (I think) that wedge 1 and 2 are there to balance the rise in emissions due to the extra cars.

• Frederik De Roo says:

What I was trying to say (but didn’t really say) was that it’s not the current emissions that are responsible for 2 Gton/yr, but the projected emissions in 2054 – if I understand them correctly.

• John Baez says:

Will wrote:

Do you have any idea whether auto emissions are indeed responsible for 2 gigatons of carbon per year?

Nobody is claiming that. Pacala and Socolow claimed that cars put out 0.5 gigatons of carbon per year in 2004. They predicted that would quadruple by 2054 unless we did something about it. That’s where the number ‘2 gigatons per year’ comes from.

Remember, each of their stabilization wedges is supposed to cut carbon burning 1 gigaton by 2054, like this:

But they don’t start out saving 1 gigaton right from the start.

If you want me to check that cars burnt about 0.5 gigatons of carbon in 2004, I will. I think it’s good practice to check these things myself — there are lots of ways to look up numbers using Google, and it even has a built-in calculator.

Unrelated tangent: I have a bit of a pet peeve that lots of climate change talk refers to absolute amounts of carbon (or some amount of carbon per year) but unless you’re very familiar with the topic (and I’m unfortunately not) it’s hard to put things in perspective.

Yeah, I have the same pet peeve! The only solution is to learn this stuff. That’s why I started the page Carbon emissions, to help me remember some numbers. Let’s all keep improving this page — it’s not very good yet.

In 2007 the world burnt 8 gigatons of carbon — 8 billion tons. So, that’s a bit more than 1 ton per person. But if you’re a typical American you burnt 5 tons. These numbers are not too hard to remember.

Here’s a graph showing how it’s gone up, along with the amount of carbon dioxide in the air… and some different future scenarios:

The graph on the bottom says ‘CO2 emissions’ but if you look carefully you’ll see it says ‘GtC/yr’, which means gigatons of carbon per year. You have to be careful about carbon versus carbon dioxide — that’s another easy way to get mixed up.

And if you look carefully, you’ll see that because we burnt 8 gigatons of carbon in 2008, so far we are roughly following the dark red curve — the worst scenario shown here.

But even the worst scenario shown here has us burning less than 3 gigatons of carbon per year by the end of the century. One can easily imagine still worse scenarios!

• Will Robertson says:

Thanks for the detailed reply! To me 0.5 gigatons for vehicles vs 8 gigatons total seems around about the right order of magnitude. (To go back to my previous point, if they’d said “10% of today’s carbon emissions”, instead, perhaps the numbers would have been more accessible? I realize I’m being rather speculative here.)

i think the work you’re doing with the azimuth project is really important to get a common reference point for all of these figures — I know it’s only early days yet but great work so far!

• John Baez says:

Thanks!

Yes, here’s always the question of how often I should remind people (including myself) of various numbers. In this particular series of posts I’m mainly going through what Pacala and Socolow said, with just a little effort spent on making it easier to follow. The reason is that I plan to go through lots of ‘plans of action‘, of which theirs is only the first. So I feel I should ration my strength. The goal is to build up a nice summary of all these plans on the Azimuth Project, and then start comparing them.

And here’s a note to everybody out there reading this:

If you have any questions about numbers and what they really mean — like, what are the total carbon emissions of cars on this planet, and what percent is that of total carbon emissions — I hope you ask! Someone here will surely be very happy to answer.

11. jack fuller says:

I’m a well over the hill retired engineering physicist who finds himself reluctantly, but for necessary enough reasons caught up in local community politics. As such, my role sometimes becomes the reality reminder in the often fetid chore of politics.

So pardon my political kibitzing habit, to wit: It seems unfortunately necessary to keep in mind how important details such as herein discussed can nowadays be summarily if not derisively dismissed by political forces (or ‘torques’ — ‘spin’?). The task is now not only the discovery of truth but the marketing of truth!!

• John Baez says:

Hi, Jack – nice to meet you, welcome to the club! Better over the hill than under the hill, that’s what I always say.

The task is now not only the discovery of truth but the marketing of truth!!

Yes indeed. I’m aware that after the latest election, the US House of Representatives looks like this:

where red means not ‘Republican’ but ‘a state having a congressperson who has expressed skepticism about human-caused global warming’.

So, people who believe that global warming is a serious problem have a lot of marketing to do — especially in the US, but also elsewhere.

Luckily, there are lots of blogs that discuss the politics of climate change. So, I’ve decided to keep political discussions out of this particular blog. Once people start talking about politics, it becomes very hard to talk about science in a productive way. In politics, any expression of uncertainty or doubt is a weakness — while in science, it’s crucial.

Indeed, even the map above is pushing the limits of this blog’s rules &mdashl I can get away with it because I’m the boss. And you’ll notice I didn’t say whether this sea of red was a good thing or a bad thing.

But please, join our conversation about the science and feel free to use facts you learn here to clobber your debating partners back at the local coffee shop.

12. John Baez says:

We got into some discussion here of how much increases in automobile efficiency would reduce CO2 emissions, due to the ‘rebound effect’ or ‘Jevons effect’.

Here are some people bringing data to bear on this question! I think that’s important: I don’t think one can settle this by theoretical arguments.

* Kenneth A. Small and Kurt Van Dender, Fuel efficiency and motor vehicle travel: the declining rebound effect, 10 April 2006.

We estimate the rebound effect for motor vehicles, by which improved fuel efficiency causes additional travel, using a pooled cross section of US states for 1966-2001. Our model accounts for endogenous changes in fuel efficiency, distinguishes between autocorrelation and lagged effects, includes a measure of the stringency of fuel-economy standards, and allows the rebound effect to vary with income, urbanization, and the fuel cost of driving. At sample averages of variables, our simultaneous-equations estimates of the short- and long-run rebound effect are 4.5% and 22.2%. But rising real income caused it to diminish substantially over the period, aided by falling fuel prices. With variables at 1997-2001 levels, our estimates are only 2.2% and 10.7%, considerably smaller than values typically assumed for policy analysis. With income at the 1997 – 2001 level and fuel prices at the sample average, the estimates are 3.1% and 15.3%, respectively.

Here are some other references:

• UKERC, The rebound effect report.

* Evan Mills, Efficiency lives – the rebound effect, not so much, RealClimate, 13 September 2010.

* H. Herring and S. Sorrell, eds., Energy Efficiency and Sustainable Consumption: Dealing with the Rebound Effect, Palgrave Macmillan, Basingstoke, 2008.

* S. Sorrell, J. Dimitriopolous and M. Sommerville, Empirical estimates of direct rebound effects: a review, Energy Policy 39 (2009), 1356-1371.

Abstract: Improvements in energy efficiency make energy services cheaper, and therefore encourage increased consumption of those services. This so-called direct rebound effect offsets the energy savings that may otherwise be achieved. This paper provides an overview of the theoretical and methodological issues relevant to estimating the direct rebound effect and summarises the empirical estimates that are currently available. The paper focuses entirely on household energy services, since this is where most of the evidence lies and points to a number of potential sources of bias that may lead the effect to be overestimated. For household energy services in the OECD, the paper concludes that the direct rebound effect should generally be less than 30%.

I also see people claiming there’s a difference between the rebound effect and the Jevons effect – I’m not sure what that’s about. There’s also the ‘Jevons paradox’, when the rebound is so great that increases in efficiency actually increase total consumption. We can say the Jevons paradox happens only when the price elasticity of demand is actually less than -1, while the rebound effect occurs whenever it’s negative.

(See the Azimuth Project for more explanation.)

13. Willis Eschenbach says:

John, thanks for an interesting article. You say:

But before I even list any of their stabilization wedges, I should emphasize: stabilizing emissions at 7 gigatons is not enough to stay below 500 ppm forever!

Unfortunately, unless I missed it (always possible), none of the citations you offered provided any support for your claim. What are you basing it on?

Finally, the accuracy of the Bern Model used in carbon calculations is far from known. Among other things it has several variables which give very different results depending on their settings. Different values for these variables have been used in different IPCC reports … and they can’t all be right. And that’s just on the implementation side.

Regarding problems with the Bern Model, see e.g. Jacobson in the Journal of Geophysical Research.

Many thanks,

w.

• John Baez says:

The references I linked to analyze the question of how much CO2 stays in the air a given time after it’s been put in. If any of the current widely accepted guesses for how this works are remotely close to correct, carbon emissions at the 2004 level of 7 gigatons/year would eventually push CO2 above 500 ppm.

This is also claimed by the paper I’m summarizing. If you look at the supposedly more precise curves drawn by Pacala and Socolow, instead of the linear approximations, you’ll see the bottom curve slopes down:

They say the bottom curve is a “CO2 emissions path consistent with atmospheric CO2 stabilization at 500 ppm by 2125 akin to the Wigley, Richels, and Edmonds (WRE) family of stabilization curves described in [11], modified as described in Section 1 of the SOM text.”

Here reference [11] is:

• T. M. L. Wigley, in The Carbon Cycle, eds. T. M. L. Wigley and D. S. Schimel, Cambridge U. Press, Cambridge, 2000, pp. 258–276.

The “SOM text” is the supporting online material for Pacala and Socolow’s paper, which you can get if you or your institution have a subscription to Science. If we want to discuss this in a serious way, one of us should get ahold of that.

Finally, one can get rough feel for this issue here:

Click for some references.

I wish I had the software to crank out what different models predict about CO2 concentrations given different carbon emissions curves. Then I could feed in a constant 7 GtC/year curve and see what they say. The above graph doesn’t directly this issue, but it’s pretty clear that in the model used to compute that graph, carbon emissions have to drop below 7 GtC/year to keep CO2 below 500 ppm.

And, these curves don’t need to be very close to correct for this to be true!

• Willis Eschenbach says:

1. As my citation to the Jacobson paper shows, the length that carbon dioxide stays in the air (e-folding time) is far, far from as settled as you claim.

2. I ran the numbers myself, and I got an e-folding time of about 35 years. Jacobson gives a very similar number.

3. At the e-folding rate shown by Jacobson (one of the planet’s best climate modelers), at 700 ppm level emissions the CO2 stabilizes below 500 ppm.

4. There is no agreement on the proper settings for the Berne model. Different modelers pick different numbers and get different answers. Different numbers were used in the SAR, TAR, and FAR reports. Perhaps you could tell us which numbers were right, and which were wrong, and why …

5. Contrary to your claim, the Bern model can easily forecast the levels below 500 ppmv. This is because it has no less than SEVEN tunable parameters (f1, f2, f3, tau1, tau1, tau3, and tau4). And unfortunately, nobody has yet found any way to say what the proper settings are. We don’t have enough data yet. So what we have is nothing but Von Neumann’s parameterized elephant

In short, I fear you have fallen into what I call the “climate trap”, where after sufficient repetition, a number of unverified (and at present unverifiable) ideas (like the idea that 7 gTC emissions will keep us below 500 ppmv) are presented as gospel truth. They go so far as to compare their results from their own model (the “Wigley Model”) to what they call the result (singular) of the Berne Model … as if there were only one result possible from the Berne Model.

The gospel truth about carbon is that so far, we don’t have enough knowledge to properly set the dials on the Berne model. But when I read the Pacala/Socolow paper in 2004, I threw it out the window.

Why? Well, I was having trouble with their unquestioned acceptance of their own carbon model (the “Wigley model”), a common failure in modelers. But I tossed the study when I read this line:

In our BAU emissions scenario, carbon emissions grow 1.5%/y and double in 50 years. If, as well, the economy were to grow at 3%/y, then, in 50 years, the economy would quadruple, and its carbon intensity would fall to half its original value.

Since whoever wrote that clearly does not understand the intricacies of the magic of compounding interest and never heard of the “rule of 70”, and since a carbon model is nothing but a model of compound (negative) interest, I knew I had left science and was wandering among climate scientists. I prefer people who actually do the math before they write the papers.

• DavidTweed says:

I’m trying to understand what you mean by

Since whoever wrote that clearly does not understand the intricacies of the magic of compounding interest and never heard of the “rule of 70″,

So the heuristic gives a doubling time of 46 years, the actual doubling time is about 46.56 years. However, I don’t see why inaccuracy of 3.5 years to presumably get a round figure for a written repot implies problems with their science. Could you expand on what is actually incorrect about what they’re saying?

• DavidTweed says:

A better phrasing would have been “I don’t see why a rounding up introducing an inaccuracy of 3.5 years to presumably get a round figure”. I also can’t find any problem, except another 3.5ish year round up for the 3 percent quadrupling time, with any of the rest of that quote. (I can understand this is a very, very simplified model which one might object to, but you seem to be suggesting something a numerical error.)

• Phil Henshaw says:

I quite agree Willis that “The gospel truth about carbon is that so far, we don’t have enough knowledge to properly set the dials”. One factor most people don’t discuss is the “dirty” truth that carbon fuels are going to continue to be the cheapest source of energy, and since all the mitigation strategies are predicated on only marginal growth restraint, the proposed technologies probably won’t work economically.

As to the economy x4 in 50 years and the carbon intensity (per \$) 1/2 I think that’s exactly the BAU rates.

This shows the IEA historic data for GDP, energy and energy efficiency proportioned to their growth rates along with the ratios for their growth rates. With notes from a talk I gave on it at fyi:

http://www.synapse9.com/pub/EffMultiplies.htm

• John Baez says:

Willis wrote:

There is no agreement on the proper settings for the Berne model. Different modelers pick different numbers and get different answers. Different numbers were used in the SAR, TAR, and FAR reports. Perhaps you could tell us which numbers were right, and which were wrong, and why …

Alas, I’m just trying to learn this stuff. I find that the fastest way is to talk about it in public, so people can chip in with extra information, and do their best to find mistakes in what I write.

You’re claiming that there’s so much uncertainty that we can’t use these models to aid us in decision-making. Other people say otherwise. I’ll only be able to have an interesting opinion on this question after I learn more.

Since whoever wrote that clearly does not understand the intricacies of the magic of compounding interest and never heard of the “rule of 70″, and since a carbon model is nothing but a model of compound (negative) interest, I knew I had left science and was wandering among climate scientists.

I think that’s unfair, both to climate scientists as a whole, most of whom don’t deserve this sort of abuse, and also to Pacala and Socolow. This remark of theirs:

In our BAU emissions scenario, carbon emissions grow 1.5%/y and double in 50 years. If, as well, the economy were to grow at 3%/y, then, in 50 years, the economy would quadruple, and its carbon intensity would fall to half its original value.

may lead you to think they’re confused. But since Socolow is a professor of mechanical engineering at Princeton, and Pacala did work on mathematical biology as a grad student at Stanford before going on to direct the Princeton Environmental Institute, I suspect that in fact at least one of them understands compound interest.

And indeed, if the economy grows at 1.5% for 50 years, it will grow by a factor of about 2.105. If it grows at 3% for 50 years, it will grow by a factor of about 4.38. I don’t think it’s bad, in the context at hand, to say “double” and “quadruple”. It’s not as if the conclusions would be affected by the extra decimals!

To me, the important part of Pacala and Socolow’s paper is their list of gigaton-carbon-per-year “wedges”, which takes the overall issue of carbon emissions and breaks it into pieces that are easier to grasp and argue about.

14. Phil Henshaw says:

The irony I see is that when someone point out the importance of looking at the wall we’re running into, others tend to see the solution as finding ways to keep running toward it ever faster,… Isn’t that how we’re all treating the problem of natural limits, seeing the solution to resource constraint as inventing ways to consume them faster??

To me that’s the problem with the “wedges” models, a real conceptual error from the start. They draw the problem as a somewhat accountable triangle to integrate, rather than an escalating process that needs to continue somehow.

So… I corrected my dollarshadow page, with the energy figures seeming to be validated in this exchange, and the PV farm area figures corrected by a factor of 20.3. That means to generate the economy’s energy with PV (a 100% “wedge” at present growth rates) we’d need to cover the whole earth in 259 years instead of 111, but still presents kind of a problem. I can’t retrace all my steps, but that estimate of the time we have before hitting “the wall” is actually what I was always estimating before, from rough methods, until I recently laid out the calculation in a way people could check…

15. More irony: How to sell scenarios to “economists”? One, they want growth; better compounding than linear. They are (practically) forever stuck in the goldilocks period of their system. Two, they want exact numbers; even while pontificating about compound interest. They don’t get one can’t exactly predict when fluctuatingly compounding variable interests hit a ceiling. But we can predict the ceiling will be hit.

16. Phil Henshaw says:

I was referencing T.S. Kuhn recently and noticed he sort of said “don’t bother”, they’re never going to take to new ideas anyway… I have hopes of teaching people skills of observation, but still, it says we’re in a worse jam than we thought (to add to all the long overdue homework assignments we’d been ignoring…).

I’ve recently found some good response from institutional investor groups, those realizing there’s a definite problem here, but am still rebuffed by economists. Keynes even pointed out that different parts of an economic system can’t wander off by themselves, it spoils the fun… Maybe the line is between people willing to entertain the possibility we might live in a physical world where things behave by themselves and we better watch, vs. those that can’t stand that idea…

17. jack fuller says:

Just mostly idle curiosity perhaps, but who in particular are the absolute devotees of “growth”, and how is such growth defined? I consider myself a reasonably astute member of civilized, even of urban humanity, however, not only me, but the majority of my acquaintances are frankly puzzled by the preoccupation toward “growing” apparently everything from the expanse of domiciles and dwellings to the amount one can pile on a plate at restaurants and buffets.

My offhand impression of Scandinavian countries, among others, is that they are fairly stable in size of everything and seem to maintain a working equilibrium between intake and dissipation in most things that matter.

Anything to the contrary seems to me an obsessive-compulsive disorder perhaps similar to the mass “tarantella” problems in 17th century southern Italy. I hear echoes of Vance Packard from bygone years pointing out how fish fins on automobiles (or “spoilers”, nowadays) are exclusively the outcome of waking hypnotic suggestion from both commercial and intellectual advertising. Might we all hope that the “Marlboro-man” of incessant growth will someday gasp his last in the same manner as his nicotinic brother?

18. […] Part 1 of this series we talked about four wedges involving increased efficiency and conservation. In Part […]