December 2002
Section 7
Carbon Sinks
Kyoto ‘sinks’ involve
removal of atmospheric CO2
through human enhancement
of carbon storage in
terrestrial and ocean
reservoirs
The Kyoto Protocol addresses the question of
sinks in several of its articles
• includes net changes in greenhouse gas emissions
by sources and removals by sinks through
afforestation, reforestation and deforestation (ARD)
since 1990 (Article 3.3);
• additional human- induced activities (beyond ARD)
that affect sources and sinks in the agricultural soils
and forest management (Article 3.4);
• allows countries whose net flux of greenhouse gases
from land- use change and forestry activities
constituted a net source in 1990 (i.e., Australia) to
use 1990 levels as a reference (Article 3.7).
Kyoto ‘sinks’ must be considered against
background of the natural global C budget
• Primary global C budget Reservoirs
– Atmosphere:
~730 billion tonnes of carbon (GtC)
(or ~2700 billion tonnes of CO2)
– Terrestrial Vegetation, Soils and litter:
~ 2000 GtC
– Oceans
~ 38,000 GtC
•Annual Global Fluxes in a Balanced Carbon
Budget
–terrestrial to atmosphere and back (NPP ~60 GtC/year
–ocean to atmosphere and back
~90 GtC/year
For most of the past millennium, the
global carbon budget has been in balance
Directly Measured
Data from ice cores
Over the past decade, oceans and ecosystems
have offset human emissions through enhanced
natural sinks
GtC/year in 1990s
8
6.4
6
4
3.2
+
2
0
-2
-4
Energy
1.6
Deforestation
=
-
-
Atmospheric
Increase
-1.7
-3.1
Land Sink
Ocean Sink
An atmospheric perspective of the terrestrial
carbon budget
Atmospheric CO2
730 Gt
fixed by photosynthesis
Gross Primary Production
120 Gt/year
autotrophic respiration
by plant tissue
Net Primary Production
60 Gt/year
heterotropic respiration
by bacteria and fungi
Net Ecosystem Production
5 Gt/year
Human and natural disturbances
Net Biome Production
~1 Gt/year
However, this offset varies significantly from
month to month and year to year
8
Fossil fuel emissions
Annual atmospheric increase
Monthly atmospheric increase (filtered)
6
4
2
0
1960
1970
1980
1990
2000
Several important factors affect future terrestrial
carbon fluxes
• CO2/N fertilization
– Enhances rates of growth
– Alters ecosystem composition
– Saturates with time
• Warmer temperatures
– Enhances growth for cold-temperature constrained margins of species
range
– Decreases growth in warm-temperature constrained regions
– Enhances plant and soil respiration
• Changes in precipitation
– Varied response re vegetation growth
– Increased/decreased fire risks
• Land use change
The natural sources and sinks play an
important role in calculating BAU baseline for
FCCC action
IS92 or SRES
Emission Scenario
Fossil Fuel
+
Deforestation
Carbon Budget
Models
Atmospheric
Concentrations
Land
Sources &
Sinks
Atmosphere
Ocean
Sources &
Sinks
Globally, the natural land sink is
estimated to be very large
GtC/year
2
1.6
1
Actual Growth
Sink
Net Sink
0
-
-1
-2
Deforestation
Source
=
-1.4
-3
-3
-4
This sink is the aggregate of net sources/sinks
from terrestrial ecosystems for each country
Global Land Sink
(-3.0 GtC/yr)
Sources/Sinks for Each Country
Country A
Country B
Country C
=
Factors:
Natural variability
Age structure
CO2/N fertilization
Past land use and land management
Canada
Etc
There are various types of ‘human’ sinks, but all
are not equally feasible
Potential
High
Ocean storage
?
Geological storage
Suppress forest disturbances
RAD
Ocean
fertilization
No till
Ag products
Low
High
Feasibility
Almost all sources and sinks in agricultural
soils are human in origin
Title goes here
Mt CO2/year
12
10
8
6
4
2
0
-2
1960
1980
1990
Year
2000
2010
New forests accumulate carbon
very slowly
T itle g o e s h ere
Cubic meters of wood/ha/year
600
Hybrid poplar
Douglas fir
Eastern spruce
500
400
300
200
100
0
0
5
10
15
20
25
Age
30
35
40
45
50
Planting new forests can also add to
global warming by reducing albedo
British Columbia
Rest of Canada
Potential Sink
Albedo Effect
Region
FSU
Nordic Europe
Southern Europe
Eastern Europe
Southern USA
-150 -100
-50
0
50
100 150
Equivalent Sink (t C/ha)
200
250