Our carbon emissions are causing anthropogenic global warming (AGW),
which is causing future droughts, floods, famines, extreme heatwaves,
exacerbation of existing diseases, landslides,
violence, migration, even earthquakes and tsunamis. In that way,
our emissions are killing future people.
But is that really true? And what specific effects are our everyday
actions having on future people?
Lifetime theft theory addresses these issues by estimating
how much time we steal from the lives of future people when emit
carbon in everyday life, for example by driving a car or flying in an
airplane. It's a central issue in 21st-century ethics.
The 1000-tonne rule
Burning roughly 1000 tonnes of fossil carbon, or emitting roughly 4000
tonnes of CO2 (equivalent),
causes the premature death of a future person from diverse effects
of AGW.
That's
the 1000-tonne rule.
It
corresponds roughly to different estimates of the human cost of global
warming or mortality cost of
carbon,
plus or minus a
factor of 2. In other words, it lies somewhere between a 500- and a
2000-tonne rule. Here is the relevant literature:
Bressler,
R. D. (2021). The mortality cost of carbon. Nature Communications, 12(1), 4467.
Nolt,
J. (2011). How harmful are the average American's greenhouse gas
emissions? Ethics, Policy and
Environment, 14(1), 3-10.
Parncutt,
R. (2019). The human cost of anthropogenic global warming:
semi-quantitative prediction and the 1,000-tonne rule. Frontiers in Psychology, 10, 2323.
Pearce,
J. M., & Parncutt, R. (2023). Quantifying global greenhouse gas
emissions in human deaths to guide energy policy. Energies, 16(16), 6074.
The
1000-tonne rule is easy to derive. Burning a trillion tonnes of
fossil carbon altogether will cause AGW of 2°C. That will
probably cause one billion premature deaths altogether (or 10% of
future world population), spread out over a long
period of 1-2 centuries. A trillion divided by a billion is a thousand.
That is a reasonable estimate. It breaks down as follows. AGW of
2°C will cause existing death rates to increase by roughly 10m/yr
for roughly 100
years. In particular, it will cause the current death rate in
connection with poverty to rise from roughly 20m/yr (Pogge, 2005) to
30m/yr. The total death rate from any cause will then rise from roughly
60m/yr to 70m/yr. In
the following article you can read about the death rate in connection
with poverty:
Pogge,
T. (2005). World poverty and human rights. Ethics & International Affairs, 19(1),
1-7.
A
hundred years is a long time. There are two reasons for choosing such a
long time window.
It
corresponds roughly to the half-life of
anthropogenic CO2 in the atmosphere. Currently, the half life is less
than a
century, but it is getting longer as the concentration of CO2 increases.
Humanity
is taking a long time to get carbon emissions under control. Global
emissions are still roughly constant although we have been talking
about reducing them for three decades.
The
calculation also makes assumptions about the duration of a human life
when it is cut short by global warming. People in the future who die
from effects of global warming could
be very old or very young or anywhere in between. Let's suppose that
normal life expectancy without AGW, poverty or other serious stressors
is 80 years. If that is the case, the average age of a future person
who dies in connection with AGW is 40.
The 1000-tonne rule can be restated like this: when we burn 1000 tonnes
of fossil carbon, we steal 40 years from
the life of a future person. It follows that when we burn one tonne of
fossil carbon, producing about 4 tonnes of CO2, we steal 1/1000 of a
life. 40 years is 14600 days, so we steal about 15 days from the life
of a future person every time we burn one
tonneof fossil carbon
or emit 4 tonnes of CO2 equivalent.
That
happens when we take an intercontinental return flight in second
class. It's called lifetime theft.
In this way we can estimate the amount of time we steal from a future
person whenever we burn fossil fuels. We can then ask ourselves whether
that is justified or not, and adjust our behavior accordingly.
Cigarettes
To get the ball rolling, it helps to start with a familiar
example: cigarettes. Smoking one of those things steals 10 to
20 minutes from your own life. Not someone else's -- your own. To do
that, it takes 5-7 minutes. So you are stealing time at a rate that is
2 to 3 times greater than the time you are spending. Let's call that
the Lifetime
Theft Factor.
If you want to check out the detail, here is some source literature:
Jackson,
S. E. (2025). The price of a cigarette: 20 minutes of life?
Addiction.
Shaw,
M., Mitchell, R., & Dorling, D. (2000). Time for a smoke?
One cigarette reduces your life by 11 minutes. BMJ, 320(7226),
53.
Monday
Campaigns. Here’s how much time you save when
you quit smoking (rule-of-thumb: ~6 minutes per cigarette).
NHS
(UK). Quit smoking—what happens when you quit
(time course of health gains begins within minutes).
Driving
Let's say you are driving an
efficient small to medium car at
80 km/h (50 mph), which minimizes fuel consumption per km.
You
are burning 6 liter/100 km.
Burning
gasoline causes emissions of 2.31 kg CO₂/liter.
To
convert to mass of carbon, multiply by 12/44.
Burning
1,000 t fossil C (10⁶ kg C) steals 40 years or 350,000 life-hours.
To
burn that will take you 38 years or 331,000 hours.
You
steal one hour from a future person for every hour that you drive.
The
lifetime theft factor for efficient driving is about 1. For every hour
you spend behind the wheel, you steal an hour from the life of a future
person. Seen in that way, driving a car is about half
as dangerous as smoking. But there is a big difference: the life you
are shortening is not your own. It is someone else's.
Flying
Flying is much worse. The lifetime theft factor is about 25 in economy
class and higher otherwise. For every hour that you fly, you typically
steal from a future person:
one
day if you are seated in economy
class
2
days in business class
4
days in first class
10-30
days in a private jet
Let's
calculate that:
CO2
emissions per economy-class passenger on a long-haul flight are 120
gCO2/km.
Aircraft
emit other gases and particles that contribute to the greenhouse
effect. A typical and often cited value for the radiative forcing coefficient for
aviation is RFI = 2.7.
The equivalent emissions per passenger are therefore 324 gCO2e/km.
The
distance traveled to emit 1/1000 of that (3.7 tCO2e), killing 1/1000 of
a future person (i.e., stealing 1/1000 of a life), is 11,419 km.
Average
cruising speed is 850 km/h.
Cruising
flight time to emit 3.7 tCO2e (killing 1/1000 future person) is
therefore 13.4h.
The
average age of a future person killed by effects of global warming
will
be about 40 years.
It
takes 13.4h to steal 40/1000 years = 350 hours.
Therefore,
the
ratio of time stolen to time spent flying is 350/13.4 = 26. For every
hour that we fly in economy class, we steal a
day from the life of a future person. For background about
comparing economy with business and so on, see:
Gössling,
S., & Upham, P. (2012). Introduction:
aviation and climate change in context. In Climate Change and Aviation
(pp. 1-23). Routledge.
Clearly, flying is immoral. At the very least, it should be much more
expensive (carbon tax). Frequent
flyers should be especially penalized. Rationing is a possibility.
Beyond that, flying should be reserved for emergencies, and private
jets should be
banned.
Acknowledgment.
This page was inspired by an email exchange with David M. Carter, who
developed a similar measure called "flight time factor".
The opinions expressed on
this page are the
authors' personal
opinions.
Suggestions
for improving or extending the
content are
welcome.
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