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Why We’ll Need More Than
Seven “Stabilization Wedges”
Sustainability Institute
10 Jan 08
Lead Modeler
Credit
Dr. Tom Fiddaman, Ventana Systems
http://www.metasd.com/index.html
Modeling and Framing
Dr. John Sterman, MIT
http://web.mit.edu/jsterman/www/
Modeling, Framing, and Presentation
Design
Andrew Jones, Sustainability Institute
http://www.sustainabilityinstitute.org/
18 B
700
12 B
600
ppm
TonC/year
24 B
If Fossil Fuel Emissions Follow the
“Business as Usual” Path, CO2 in the
Atmosphere Will Pass
the Goal of 450
CO2 in the Atmosphere
Fossil Fuel Emissions
800
ppm
6B
500
Goal
0
2000
2020
2040
2060
2080
2100
This is comparable to the
IPCC “business as
usual” future
400
300
2000
2020
2040
2060
2080
What would it take to get CO2 in the
atmosphere to stabilize under 450 ppm?
How to get the blue line to fall to here?
2100
The Wedges Plan Proposes a “Flat path”, Leveling
Emissions Through 2054 and Then Reducing Them
So what
would
happen to
CO2 in the
atmosphere?
Would we
meet the
goal?
Socolow and Pacala
How close to our goal would the “Flat path”
bring us (With no “post 2050” reductions)?
What if fossil fuel emissions flattened at
2007 levels? Sketch in the curve you
think would result on the graph to
the right.
Fossil Fuel Emissions
CO2 in the Atmosphere
800
24 B
700
600
12 B
The “flat path”
Draw a line
starting here
ppm
TonC/year
18 B
500
6B
0
2000
400
2020
Why?
2040
2060
2080
2100
300
2000
2020
2040
2060
2080
2100
WeSimplified
Will Run
Experiments
Carbon
Cycle Sector in a Carbon
Cycle Model Using System Dynamics
CO2 in
Humus
Flux Biomass to Humus
Flux Humus to Atmosphere
CO2 in
Biomass
Flux Biomass to Atmosphere
CO2 in
Atmosphere
Flux Atm to Biomass
<CO2
Emissions>
Flux Atm to Ocean
CO2 in
Mixed Layer
Diffusion Flux
CO2 in Deep
Ocean
We Simulated a Future Where We Just
Level Emissions Along the “Flat Path”
With no “post 2050”
CO2 in the Atmosphere
reductions
800
24 B
700
18 B
600
ppm
TonC/year
Fossil Fuel Emissions
12 B
500
The “flat path”
6B
0
2000
Goal
400
2020
2040
2060
2080
2100
300
2000
2020
2040
2060
2080
2100
When emissions follow the “flat path,” CO2 concentrations only
grow more slowly. Why?
Think of CO2 in the Atmosphere as a Bathtub
Emissions
CO2 in the atmosphere
The tub is filled by
emissions and drained
by net removals into
oceans and biomass.
The inflow is roughly
double the outflow
Net Removals
The “flat path” caps emissions above
removals. More is still flowing into the bathtub
than is flowing out! So the level of water in the
bathtub continues to rise.
Emissions Still Exceed Removals
Total Emissions and Removals
24 B
So CO2 in the
atmosphere continues
to increase.
18 B
800
12 B
The “flat path” for emissions
Net removals
6B
675
ppm
TonC/year
CO2 in the Atmosphere
550
425
300
2000
0
2000
2020
2040
2060
2080
2100
2020
2040
2060
2080
2100
But The Wedges Plan Also Proposes Reducing
Emissions After 2054!
Will that
make the
difference?
Socolow and Pacala
Reducing Emissions Post 2050 Puts Us On
in the Atmosphere
Track
to
Levelize
CO
2 CO2
around
550 ppm
Fossil Fuel Emissions
800
24 B
700
600
12 B
ppm
TonC/year
18 B
6B
500
Goal
0
2000
2020
2040
2060
The “flat path”
plus post 2054
reductions
2080
2100
The outcome of the
“flat path” plus post
2050 reductions
400
300
2000
2020
2040
2060
2080
Emissions exceed net removals all the way to 2100!
2100
What Happened? Why Didn’t
Emissions Level?
Total Emissions and Removals
24 B
CO2 in the Atmosphere
800
TonC/year
18 B
12 B
Emissions
675
6B
550
Net Removals
0
2000
2020
2040
2060
2080
Goal
2100
Despite reductions, Emissions
exceeded Net Removals through
2100.
CO2 in the atmosphere will rise until
the two meet.
425
300
2000
2020
2040
2060
2080
2100
So What Will it Take To Stabilize
CO2 in the Atmosphere Below Our
Goal?
It Will Take an 80% Reduction in
CO2 in theEmissions
Atmosphere
Fossil Fuel
24 B
800
18 B
700
12 B
600
ppm
TonC/year
Fossil Fuel Emissions
6B
500
Goal
0
2000
2020
2040
2060
2080
2100
400
300
2000
2020
2040
2060
2080
At this point, emissions equal net removals by 2050!
2100
80% Reduction Brings Emissions
Down to Meet Removals
Total Emissions and Removals
24 B
Emissions
CO2 in the
atmosphere
TonC/year
18 B
12 B
Emissions
6B
0
2000
Net Removals
2020
2040
2060
2080
2100
So levels of CO2 in the atmosphere
stabilize.
Net Removals
So Meeting the Goal Will Require 7 Stabilizations,
Plus 6-7 More
About 6-7
more
wedges
Socolow and Pacala
Aggressive Sequestration (seq.)
can boost
removals
CO2 in the Atmosphere
Sources of Total Removals
800
6B
700
oceans
2.95 B
seq.
1.425 B
600
ppm
TonC/year
4.475 B
500
-100 M
1900
biomass
1930
1960
1990 2020
Time (year)
2050
2080
Goal
400
300
2000
2020
2040
2060
2080
Results with 80% reduction in fossil fuel emissions
plus 1.6 GTC/year in additional sequestration by 2050
2100
The Added Sequestration
Boosts Net Removals
Total Emissions and Removals
24 B
Net Removals with
additional
sequestration
TonC/year
18 B
12 B
6B
0
2000
Net Removals
without additional
sequestration
2020
2040
2060
2080
2100
So CO2 in the atmosphere
balances out a little earlier
and lower
More information
 Models on which the model that created these runs were
based
 http://www.metasd.com/models/index.html#Climate
 Interactive version covering some of these ideas
 http://www.seed.slb.com/en/scictr/watch/climate_change/challe
nge.htm
 http://www.sustainabilityinstitute.org/tools_resources/climatebat
htubsim.html
 http://web.mit.edu/jsterman/www/GHG.html
 Video version
 http://video.google.com/videoplay?docid=823572514333411060
1&pr=goog-sl
 Other related simulations
 http://www.sustainabilityinstitute.org/climate_change/simulation
s.html
More Notes on the Model
“Emissions” in the model is total CO2
emissions. Including land use change
emissions but not including the CO2
equivalents of other greenhouse gasses.