Energy and Human Ambitions on a Finite Planet, 2021a

9 Climate Change 142
80
CO2 ppmV annual contribution
1.50
1.25
1.00
0.75
0.50
0.25
Total Rate Now: 2.6 ppm V /yr
coal
oil
gas
0.00
1800 1850 1900 1950 2000
year
cumulative CO2 ppmV contribution
70
60
50
40
30
20
10
Total Added: 123 ppm V
coal
oil
gas
0
1800 1850 1900 1950 2000
year
Figure 9.3: Estimated CO 2 contributions
from known fossil fuel expenditures based
on chemistry <strong>and</strong> the assumption that half
of CO 2 stays in the atmosphere, while the
rest is absorbed by the ocean <strong>and</strong> l<strong>and</strong>.
Units are parts per million by volume. The
left-h<strong>and</strong> panel shows the annual addition,
adding to 2.6 ppm v per year <strong>and</strong> accounting
for the slope in Figure 9.1. The right-h<strong>and</strong>
panel is the cumulative emission to date as
a function of time—essentially adding up
all the annual emissions from the left-h<strong>and</strong>
panel. These curves are not stacked as are
the ones in Figure 9.2, so each can be read
directly from the vertical axis. Note that oil
<strong>and</strong> gas are still on the rise in the left-h<strong>and</strong>
panel: we emit more CO 2 each year than we
did the year before.
Adding all three contributions from the right-h<strong>and</strong> panel of Figure 9.3
<strong>and</strong> plotting the result on top of the Keeling Curve, 12 we find astounding
overlap in the shape—as shown in Figure 9.4.
12: . . . actual CO 2 measurements
cumulative CO2 concentration ppmV
420
410
400
390
380
370
360
350
340
330
320
310
300
290
fossil fuel prediction
280
1850 1900 1950 2000
year
CO 2 measurement Figure 9.4: Fossil fuel contribution to CO 2
(red) on top of CO 2 measurements (blue).
The red curve uses a starting point of
285 ppm v <strong>and</strong> has 49% of CO 2 emissions
staying in the atmosphere. The overlap is
remarkably good <strong>and</strong> convincing.
The curve computed from fossil fuel use overlaps the Keeling Curve
so faithfully that little mystery is left as to where the excess CO 2 in
our atmosphere originates. The chemistry <strong>and</strong> historical use of fossil
fuels are not in dispute. The only “fudge” is in what fraction of the
CO 2 emitted from fossil fuel combustion remains in the atmosphere
vs. being absorbed by the ocean <strong>and</strong> other “sinks.” Empirically, about
half stays in the atmosphere, while the rest disappears into the ocean, 13
<strong>and</strong> into plant matter that gets buried in the ground. If unaware of the
oceanic <strong>and</strong> l<strong>and</strong> absorption mechanisms, we would have overestimated
the amount of CO 2 due to fossil fuels by a factor of two (see Box 9.2).
13: . . . acidifying the ocean’s water
© 2021 T. W. Murphy, Jr.; Creative Commons Attribution-NonCommercial 4.0 International Lic.;
Freely available at: https://escholarship.org/uc/energy_ambitions.