On Indulgences and Carbon Offsets

Catholics have a notion called “Indulgences”. Wikipedia summarizes it as “a way to reduce the amount of punishment one has to undergo for sins.” In the Middle Ages, indulgences were commercialized, so wealthy people could buy themselves out of punishment (or the loss of wealth might be considered the punishment, if you want to be charitable).


In the modern world, carbon emission is a great sin. Those traveling by air sin the most. Prominent environmentalists are often targeted for hypocrisy, and those hoping to avoid hypocrisy might purchase “Carbon Offsets“. These are the more equivalent of commercial indulgences. The airlines offer them to guilt-ridden passengers.

Perhaps the most obvious, ‘common sense’, solution when demand (pollution) is in excess of supply is to expand capacity.  This is what we do with most things if we can. If our house is too small, we make it bigger. If our wallet can’t hold all of our cash and ID cards, we get a bigger one. If the internet is too slow, we add capacity. In roads, this usually means adding lanes to existing roads. Perhaps we could plant more trees to absorb more carbon pollution.

Consider for instance the Boston to London round trip. It is 3255 miles each way (5237 km) and 1.1799 metric tons of Carbon roundtrip. For $14.16 or 1,888 Award Miles a United Airlines passenger can support the  Alto Mayo Conservation Initiative. Objectively this is not a lot of money in the scheme of things, and maybe it will offset your trip. I don’t have the impression most travelers purchase these indulgences.

More importantly, I don’t think this scales. Some estimates below:

A Trans-atlantic flight might require 11 trees per person per flight to do a full offset.  There are about 100 million international enplanements from the US per year.  Not all are Transatlantic of course, many are Trans-Pacific or to South America, and so longer. I will leave it to a research paper to figure out total distance. So that is on the order of 1100 million trees per year (probably more) to be planted to guiltlessly offset US international air travel.  Let’s assume 5m x 5m per tree (25 m^2). 25*1100M = 27,500 million square meters to offset international aviation from the US (excluding US domestic aviation and travel in other countries. That is 27,500 km^2, or an area of about 165 x 165 km on edge per year (for say 50 years until aviation switches to biofuels). This is the size of Massachusetts.

While that is technically feasible, since the US has lots of land (and is more than 50x the size of Massachusetts, as Massachusetts is a smaller than average state), no-one is actually doing this, and the offset is over the life of the tree, not immediate, so we would need one Massachusetts per year until the end of carbon-emitting aviation to make offsets work.

I like to think in terms of queues. The environment can clear (absorb) a certain amount of CO2 per year, basically the equivalent of net zero carbon emissions. If there is a positive amount of emissions, the CO2 queues in the atmosphere, waiting to be absorbed. (And probably doing things to the environment we wish were otherwise.)

If offsets are not employed, the alternative is that the accumulated CO2 queue from US Transatlantic enplanements will continue to grow. We could pull out Kant’s categorical imperative “Act only according to that maxim whereby you can, at the same time, will that it should become a universal law.” and argue since this doesn’t scale (can’t become a universal law), you shouldn’t do it. But that’s the sort of philosophical nonsense that we hope philosophers have recovered from.

Just because it can’t solve the entire problem and can’t become universal doesn’t mean it can’t be useful to plant more trees.  Trees are good. However, while a carbon offset indulgence may absolve you from guilt on a particular trip, it cannot absolve the industry, since it cannot scale.  Imagine the number of trees required for all aviation, not just international, and for auto travel (about 10x aviation). A more serious solution is required, one which either takes CO2 out of the air more efficiently, produces less CO2 per flight (through say biofuels or electric power), or reduces the number of CO2 emitting activities like flights (and internal combustion engine car trips) (by reducing travel).

Now to be clear, if you expand the capacity of the planet to absorb pollution (i.e. plant more trees), and people pay for their pollution, the reduced cost of per unit of pollution means that people will pollute more. Drivers will travel longer, industry will use less socially efficient means for energy generation. There might be a small amount of GDP growth associated with both the geo-engineering and resource extraction, so it is not entirely a bad thing, but it may not solve your pollution problem.


Pollution Taxes and an Environmental Trust Fund

We should reframe America’s approach to pollution. Instead of addressing pollution through a regulatory regime, we should use pollution charges to allow the market to allocate the scarce resource of clean air, water, and land. A levy would be imposed on polluters proportionate to their pollution.[1] Fines above and beyond the base rate would be collected on those who exceed permitted levels with especially dangerous pollution levels.

That revenue would be dedicated to support the US Federal Government’s broad collection of agencies that monitor, regulate, protect, and restore the environment, reduce the impacts of humans on the environment, and address the problems that arise when we face environmental emergencies or just dealing with the costs of day-to-day pollution. These agencies include the Environmental Protection Agency, the National Oceanic and Atmospheric Administration, the Federal Emergency Management Agency, and large swaths of the Departments of Agriculture, Interior, and Energy among other environmental programs, as well as the Health sector. Estimates of damages from pollution[2] are similar in magnitude to the budgets of the listed government agencies.[3]

As pollution diminishes, funding declines, pollution control and remediation programs would shrink naturally, since they are not needed as much. If pollution rises, the revenue increases, giving the government agencies the resources needed to address the problem and compensate those polluted upon.

A bipartisan Blue Ribbon Commission appointed by the National Academies would be appointed to recommend rates annually based on the best science and economics of the damages that pollution causes (so if avoidance is cheaper than accepting damages it will be undertaken). Any polluter could reduce their taxes by limiting their emissions. Polluters that find that cost-effective will do so. The rates would be phased in over 5 years to allow smooth and economically efficient transitions.

This proposal lowers expenditures on the discretionary budget from general revenue by pulling the listed agencies off the unified budget. This frees up budget resources that could be used for income tax reform, negative income taxes for people with low incomes, or lowering the budget deficit.

The Environmental Trust Fund, supported by a pollution tax, would incentivize the market to determine the best ways to reduce pollution, rather than relying on government regulations and industrial policies ranging from subsidies and loans to tax credits for favored sectors. Internalizing these negative externalities would reward what we want (pollution reduction) and discourage what we don’t (pollution). This would let individuals and organizations figure out best ways to reduce pollution. It would also provide opportunities for significant tax reforms on the general revenue ledger.

[1] For the purposes here pollutants are those that contaminate an environment with manmade wastes. Air pollutants include (but are not limited to) EPA criteria pollutants Pb, SOx, NOx, Hydrocarbons, CO, PM10, PM2.5, as well as ultra fine particulates, and CO2 and other greenhouse gases. Water and land pollution rules would also be established. Other pollutants as defined by the Blue Ribbon Commission would also be appropriate for taxation.

[2] Knittel, Christopher (2012) “Cleaning the Bathwater with the Baby: The Health Co-Benefits of Carbon Pricing in Transportation” estimates a gas tax on the order $1/gallon would cover the social costs of carbon from cars, and “reduced air pollution would substantially ameliorate the costs of an increased gasoline tax”. This is substantially lower than fuel taxes in many countries. In the US, current gas taxes vary by state but are on the order of $0.40-0.50/gallon (state + federal)

[3] According to the US Energy Information Administration, the US currently consumes about 134b gallons of gasoline annually. http://www.eia.gov/tools/faqs/faq.cfm?id=23&t=10. At $1/gallon dedicated to the ETF, this would raise about $134b (ignoring short run demand response, which is likely on the order of 10%). The actual rates should be determined by the Blue Ribbon Commission. Similar magnitudes of revenue could be raised from pollution taxes on from other economic sectors besides transportation, particularly electricity generation. These funds would be distinct from highway user fees dedicated to road infrastructure.

Current budgets of selected agencies (not all of which are pollution related):

Are environmental regulations truly transportation bottlenecks?

I recently had dinner with Fred Salvucci in Santiago Chile, among other topics, he talked about complaints about environmental regulation. He made a point any queueing theorist could appreciate. He argued that environment regulations are not slowing down transportation projects as a whole. There is only so much federal (and state) funding, and that is the real bottleneck. Loosening environmental regulations will not make any more projects get built in any given year.

UPDATE 9/16/2016

He adds ” A further concern that I have is that many DOTs are most concerned with maximizing construction volume, so are likely tempted to skew their candidate projects towards the simpler to get through the environmental process. These projects may actually be the least important ones to actually implement, so there is likely a perverse outcome in terms of project portfolio.”

Of course it may affect the sequence of projects, projects with more environmental problems, or more social impacts which induce well-heeled people to use environmental regulations as a roadblock, may get deferred for simpler projects without such problems. But shouldn’t they in a functioning democracy?

If environmental costs are real, and we think they are, that should make projects more expensive in order to ameliorate such costs, either through avoidance of creating the damages in the first place, or compensating the losers. This higher costs reduces the number of projects that can be done with the money. So it goes. All the low hanging fruit was eaten years ago.

If those projects still pass a Benefit / Cost test after amelioration, then sure, build them. That is of course less likely than if transport investments export environmental costs to the health sector or agriculture, or property values, or anywhere else that it is not properly accounted for.

Motor-vehicle-pollutants portion rising?, falling?, what?!

Alan Kandel asks at Science Blog: Motor-vehicle-pollutants portion rising?, falling?, what?!

Consult most news sources these days – this one included – when it comes to poor air quality, and what you’re likely to uncover is that more often than not in the blame-game, traffic – more specifically, tailpipe emissions – is named. Obviously, not the only source of pollutants, nevertheless, the portion of pollutants coming from traffic – and transportation, more universally – is sizable.

Falling gasoline prices: What effect is this having on both motor vehicle and public transit use and, by extension, what, if any, impact has the decline had and having on the quality of our air.

He cites my earlier post

David Levinson in “Mount Transit, Mount Auto, Mount Next,” at the Transportationist Blog, clues us in.

“In the US, we have seen a great struggle play out in the twentieth century between what David Jones calls Mass Motorization and Mass Transit. The conflict between the modes continues to this day, and has become a morality play in the culture wars. While they mostly serve different markets, they compete for users, and roadspace, and funding, and the hearts and minds of travelers. They are competing on old turf though, …, both modes appear to be in decline, transit for decades, the decline of the auto-highway-system is just beginning.”

This is an interesting revelation, because what this tells me is pollution from both sources should be becoming less and less, that is, as long as the mode-split-relationship (and other influencing factors) has not significantly varied.

He doesn’t outright state a final conclusion to the question, though he says:

But, then I noticed something interesting. The overall trend was positive between 1961 and 2007, taxed gallons going from 60.006 billion in 1961 to 177.394 billion in 2007. After the Great Recession hit just subsequent to this, the number of gallons of gasoline taxed dropped to 171.229 billion in 2008, dropping even more to 168.551 billion in 2009, rose again in 2010 to 171.101 billion, falling to 168.722 billion in 2011. Only if there are fewer less-fuel-efficient vehicles on the road coupled with greater use of cleaner-burning fuels and/or less traffic on the roads coupled with greater use of cleaner-burning fuels – along with the dip in the amount of gallons of gasoline taxed, am I able to conclude that emissions emanating from motor vehicles are also fewer. That’s a good sign even if the number of motor vehicles on America’s roadways experiences level or upward growth.


Nature is Rebounding: Land- and Ocean-sparing through Concentrating Human Activities

I subscribe and listen to the Seminars About Long Term Thinking Podcast by the Long Now Foundation.

So I was surprised and pleased to find the most recent episode featured Jesse Ausubel, (previously mentioned on this blog, and who has a lobster named for him) discussing fascinating trends in dematerialization, and how the environment is recovering (mostly) even without concerted public policy.

The blurb says:

In the field of environmental progress the conflict between anecdote and statistics is so flagrant that most public understanding on the subject is upside down. We worry about the wrong things, fail to worry about the right things, and fail to acknowledge and expand the things that are going well.

For decades at Rockefeller University Jesse Ausubel has assembled global data and trends showing that humanity may be entering an exceptionally Green century. The most important trend is “land-sparing”—freeing up ever more land for nature thanks to agricultural efficiency and urbanization. Ausubel notes that we are now probably at “peak farmland“ (so long as we don’t pursue the folly of biofuels). Forests are coming back everywhere in the temperate zones and in many tropical areas, helped by replacing wild logging with tree plantations. Human population is leveling rapidly and we are now probably at “peak children.” Our energy sources continue to “decarbonize,” and a long-term “dematerialization” trend is reducing the physical load of civilization’s metabolism.

In the ocean, however, market hunting for fish remains highly destructive, even though aquaculture and mariculture are taking off some of the pressure. In this area, as in the others, rigorous science and inventive technology are leading the way to the mutual flourishing of humanity and nature.


At my conference on the future of methane in Fort Worth last November, I found out about a documentary called Switch, about the future of energy in the US. I finally got around to getting and watching.  It is highly recommended for those interested in the subject.

It is largely non-partisan (though the protagonist is a geologist) and covers all of the important energy types in a serious and engaging way, with a bit more meat and less chrome than the typical PBS science show. You have to request a copy from the website, it is not available on iTunes or Netflix yet.

I don’t agree with everything.  I think it overestimates how long the switchover to renewables + nuclear being the largest share of energy  will take. It does this because it underestimates future technology advances — looking more linearly and less exponentially/logistically in terms of technology development and deployment. Similarly it underestimates the ability of larger inter-connected networks to mitigate reliability/availability problems from solar and wind, and advances in storage of various types. I don’t think this change will be overnight, but I hope it will be sooner than the 50 years the film estimates. The cost curves on solar and wind are getting very competitive, and the more interest they have, the more investment they will get.

Car Emissions vs. Car Crashes: Which One’s Deadlier? The answer actually surprised us.

Eric Jaffe at CityLab discusses my post from Monday:

The ever-thought-provoking David Levinson posed a question at his Transportationist blog earlier this week that’s worth a longer look: Are you more likely to die from being in a car crash or from breathing in car emissions? If your gut reaction is like mine, then you’ve already answered in favor of crashes. But when you really crunch the numbers, the question not only becomes tougher to answer, it raises important new questions of its own. …

Death by car: Are you more likely to die from a crash or breathing its toxic emissions?

Should you fear more getting hit by a car, or breathing in its toxic emissions?
I recently engaged in a conversation with my colleague Julian Marshall about which kills more : Deaths by vehicles (cars plus trucks) from crashes or deaths by vehicles from air pollution. I of course defended the “honor” of transportation and said death by crashes was much larger, he is an environmental engineer looking at air quality, and thought that was very important too. (He also argues death from car emissions is just as “honorable” as actually getting hit by a car.)
It turns out, Deaths by Crashes is larger, according to official sources, but not as much as I expected. And, the answer depends on what metric you use.
In the US, according to the Global Burden of Disease Study (Data Link), for 2010, for men+women:
road injury + other transport injury total air pollution
Deaths: 15 36
DALY: 797 624
Years of life lost: 653 565
Notes: Units: deaths per year per 100,000 people; DALYs [Disability Adjusted Life Year] per year per 100,000 people. Air Pollution is Ambient Particulate Matter air pollution and Ozone, not just transport related pollution deaths. Road injury plus other transport injury is comprehensive, the vast majority are road injuries, the large majority of which are due to car. This  includes things like driving off a cliff as well as driving into pedestrians.
Those numbers include only fine particles (PM2.5) and ozone. Using the numbers above, air pollution is worse than crashes in terms of total deaths, but not in terms of DALYs and Years of life lost.
We also need to figure out the fraction of total air pollutio n that is due to road transport.
Julian says:
Just as estimating deaths from air pollution is inexact (no death certificate says “air pollution” as cause of death; instead rates of outcomes like heart attacks are elevated slightly in the presence of air pollution), so too it is inexact to estimate contributions from specific sectors (e.g., road transport) to the air pollution total. Some PM2.5 is emitted directly and some pollution forms in the atmosphere from chemical reactions of precursor emissions; the latter type (called “secondary PM2.5”)  is harder to attribute.
An MIT study estimates that proportion at 25%. Notably they also come up with more annual deaths from air pollution at about 200,000 per year in the US (rather than the 100,000 or so the GBS study implies). Air pollution deaths (premature strokes, heart attacks, lung problems, and so on) on average shortens life by 10 years per person who dies from air pollution. Car crashes are more likely to shorten life of younger persons, hence the greater years of life lost per death.
Julian says:
The most useful number to look to, from an overall health standpoint, probably is the DALYs, since that number includes both mortality and morbidity (death and disease).
Accounting for uncertainty, to a first approximation the numbers above are roughly comparable to each other, for the two causes.
 I would conclude we should fear crashes more than air pollution from traffic, but we should not be sanguine* about emissions either.

*Our temperments of course are affected by the air we breathe.

Green cities are more pleasant

In the early twentieth century, people fled over-crowded cities for suburbs, or at least lower-density areas of the city, in part because of the poor environmental quality. While water quality in cities has significantly improved, and sewers are sanitary, and horses no longer befoul our streets, today still, air quality in cities is usually worse than in lower density areas.

Street Araber, c. 1976, Baltimore Maryland
Street Araber, c. 1976, Baltimore Maryland

Recent research by University of Minnesota colleagues reports:

Results: The proportion of physically active individuals was higher in high- versus low-walkability neighborhoods (24.9% vs. 12.5%); however, only a small proportion of the population was physically active, and between-neighborhood variability in estimated IHD mortality attributable to physical inactivity was modest (7 fewer IHD deaths/100,000/year in high- vs. low-walkability neighborhoods). Between-neighborhood differences in estimated IHD mortality from air pollution were comparable in magnitude (9 more IHD deaths/100,000/year for PM2.5 and 3 fewer IHD deaths for O3 in high- vs. low-walkability neighborhoods), suggesting that population health benefits from increased physical activity in high-walkability neighborhoods may be offset by adverse effects of air pollution exposure.

Over the coming decades however, hybrid-electric and electric vehicles are likely to be more common, if not the only vehicles allowed on city streets. The smell of the city will change. EV cities will be less polluted and much nicer, and thus more attractive than earlier polluted cities, or cities without such vehicle-type regulation. It will come a time that not only will cities be better for the global environment, resulting in less overall carbon emissions than lower density areas with greater distances and fewer shared walls, but they will be as good (if not better) for the individuals residing in them, with less overall pollution per capita and perhaps lower pollution intake than suburban areas.