north america in the global carbon cycle what is the role of north america in the emissions of...
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North America in the Global Carbon Cycle
• What is the role of North America in the emissions of fossil fuel CO2? What will future trends be?
• What is the role of North American vegetation in the global carbon cycle? Why do we think there is a vegetation sink, and what may the course be in the future?
• How can we understand and monitor North American sources and sinks of CO2 and CH4?
The heavier temperature lines 160,000 BP to present reflect more data points for this time period, not necessarily greater temperature variability.
Climate and Atmospheric History of the past 420,000 years from the Vostok Ice Core, Antarctica, by Petit J.R., Jouzel J., Raynaud D., Barkov N.I., Barnola J.M., Basile I., Bender M., Chappellaz J., Davis J. Delaygue G., Delmotte M. Kotlyakov V.M., Legrand M., Lipenkov V.M., Lorius C., Pépin L., Ritz C., Saltzman E., Stievenard M., Nature, 3 June 1999.
Antarctic Ice Core Data
Global CO2 cycle
1950
1960
1970
1980
1990
Year
Historical consumption of fossil fuels.
Emissions have increased by 2X since 1970, but there has not been a corresponding rise in the annual increment of CO2. In 1970 ~75% of the emitted CO2 stayed in the atmosphere, but only ~40% in 2000.
3800
6500
Global Fuel Use
7800 in 2005!
60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00
0.0
0.2
0.4
0.6
0.8
CO
2 A
irbor
ne F
ract
ion
60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00 02
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Year-to-year change in CO2 (ppm)
(SPO+MLO)/2
Starting year
Starting year
RECENT GROWTH IN ATMOSPHERIC CO2
CONCENTRATIONS
The average annual increase did not change much between 1970 and 2000, despite significant increases in fossil fuel emissions.
Average rate of increase per year, 1.5 ppm = 3.25 x 109 tons/yr—little change (some variations) since 1975, but possibly starting to rise by 2005.
(Manning and Keeling et al., 2006)
Changes in oxygen track the role of the land vegetation vs. ocean uptake of anthropogenic CO2.
Land uptake may have decreased at the end of the 1990s, after having increased in the early 1990s.
Fossil Fuel+ cement 5.3
Tropical Deforestation 1-2
Total 6.3 - 7.3
Global CO2 budget (PgC yr-1 ) 1980 – 1990 1990 – 2000
Sources
Atmospheric accumulation
3.2
Ocean uptake 2.1
"Missing Sink" 1-2
Total 6.3 - 7.3
Sinks
2.1 Pg C = 1 ppm atmospheric CO2 [source: Cias et al., Science 269, 1098, (1995)]Is this budget accurate? What is the scientific basis for these numbers?
Why should mid-latitude terrestrial plants absorb anthropogenic CO2? When did this uptake begin, can/will it continue?
What are the implications of terrestrial uptake for
Future CO2? US policy? Climate change?
6.5
.5-1
7-7.5
3.2
1.5-2
1.8-2.8
7-7.5
The ocean’s capacity to take up CO2 will diminish with time, as the pH
of the ocean declines due to uptake of CO2. The ocean becomes acidified.
Uptake of CO2 by chemical dissolution is limited by the rate for
exchange between deep ocean water and surface water, and eventually, by acidification of the oceans. Acidification of the ocean is likely to lead to major shifts in marine ecosystems.
Atmospheric release of CO2 from burning of fossil fuels will likely give rise to a marked increase in ocean acidity, as shown in this figure. (upper) Atmospheric CO2 emissions and concentrations, historical (—) and predicted (---), together with changes in ocean pH based on mean chemistry. The emission scenario is based on the mid-range IS92a emission scenario assuming that emissions continue until fossil fuel reserves decline.
10 0.1=25% 100.7 = 5 (!) increase in [H+].
Regional ocean- and land-atmosphere CO2 fluxes, 1992–1996.
Orange: Bottom-up land-atm. flux [Pacala, et al., 2001; Kurz and Apps, 1999 N. America; Janssens, et al., 2003, Europe; (Shvidenko and Nilsson, 2003; Fang, et al., 2001, for North Asia];
Cyan: Bottom-up ocean fluxes (Takahashi, et al., 2002),
Blue = ocean-atmosphere fluxes, inverse models,
Green = land-atmosphere fluxes, inverse models,
Magenta = land plus ocean inversion fluxes,
Red: fossil fuel emissions, subtracted from net.
Source: P. Ciais, 2006
Uptake of CO2 in the US (PgC yr-1) [Pacala et al., 2001]
Forest Trees
Dead w
ood
soil CWood Prods
Woo
dy en
croac
hmen
t
fire su
pres
s
Ag
soils
Net trade
RIver export
Category Low Hi
Forest Trees 0.11 0.15
Other Organic Matter
In Forests 0.03 0.15
Domestic Wood Products 0.03 0.07
Woody Encroachment on Non-forested Lands x-fire
0.12 0.13
Agricultural Soils 0.00 0.04
Exports Minus Imports of Food and Wood Products
0.04 0.09
Sediment Burial, River Export 0.04 0.08
Apparent U.S. Sink Including Woody Encroachment
0.37 0.71
Sink (actual net) 0.30 0.58
US "forests": Net sink: 0.3-0.6 PgC yr-1
Emissions (1996): US 1.44 Mexico 0.09 Canada 0.11
Forests in the US – and many other places – are in middle to young age classes (25-75 years), due to changes in agriculture (intensification) and forest management (intensification).
NH
% o
f lan
d ar
ea in
fore
sts
20
4
0
6
0
8
0
1
00
Year
1700 1800 1900 2000
MA
Fitzjarrald et al., 2001
A legacy: land use change in New England
-5
-4
-3
-2
-1
0 NEE = -1.28 - 0.146 x (yr-1990); R2 = 0.337
Year
1992 1994 1996 1998 2000 2002 2004
10
12
14
16
-1 x GEE
Resp
GEE = 11.1 + 0.363 x (yr-1990); R2 = 0.732
R = 9.82 + 0.217 x (yr-1990); R2 = 0.626
NEE
(Mg-
Cha-1
yr-1)
Mg-
C ha
-1yr
-1
0
20
40
60
80
100
120
Abo
vegr
ound
woo
dy b
iom
ass
(MgC
ha-1)
93 94 95 96 97 98 99 00 01 02 03 04 05
oak
other spp
Year
Rates for growth and for carbon uptake are accelerating in this 80-year-old New England Forest…why is that? Will that continue? How big do North American trees grow?
20 30 50 cm
Year
T (
C)
1900 1920 1940 1960 1980 2000
-35
-30
-25
-20
-15 January
Year
T (
C)
1900 1920 1940 1960 1980 2000
1214
1618
JulyRegional Composite T
Regional Smoothed
NOBS T
January
Decade
Mon
thly
mea
n Sn
ow (c
m)
1970 1975 1980 1985 1990 1995 2000
2030
4050
60
Thompson
LynnLake
April
Decade
Mon
thly
mea
n Sn
ow (c
m)
1970 1975 1980 1985 1990 1995 2000
510
1520
2530
Changing climate and C: an example from NOBS flux site, Thompson, MB
Snow cover
Temperature
PEAT
45% cover
Deviation from the 9-year means of annual Net Ecosystem Exchange (upper, g C m-2 ), temperature (middle, C), and two-year precipitation sums (lower, cm), illustrating the critical role hydrology plays in determining the annual carbon balance at a mature black spruce forest.
P2 (mm/2yr)
NEE
(kgC
/ha/
yr)
85 90 95 100 105 110 115
-40
-20
020
4060
r2=.72 p<.0035 slope=-3.5
Precipitation (mm in 2 yr)
(gC
m-2 y
r-1)
Up
take
| em
issi
on
Annual NEP, 1994-2004
Thompson, MB
T : warmer
Precip: wetter
Water table depth and hydrology are key factors controlling the accumulation or ablation of peat. 95 96 97 98 99 00 01 02 03
Year
73
40 41
13 12
-11-26 -30
-49-50
0
50
-2
0
2
-15
0
15
1995 1996 1997 1998 1999 2000 2001 2002 2003
-15
0
15
-2
0
2
-
50
0
5
0 Net CO2 echange
Annual T anomaly (oC)
Annual Precip Anom (mm)
02
46
8
Jun. 1 Jul. 1 Aug. 1 Sep. 1
-30
-20
-10
0
R, measuredR, modelledWater table depth
Dai
ly r
espi
ratio
n, g
C m
-2
Wat
er t
able
dep
th,
cm
Figure 2: interaction of WT depth and CO2 Flux from the boreal peatland in Manitoba, summer 2002
But wasn't the weather unusually cold in 2002-2003? Not over the globe….
[base yrs: 1951-1980]
Correlation: {T, soil moisture index}CCSM1-Carbon Control Simulation
DJF JJA
Positive correlation warmer-wetter; or cooler-drier
Negative correlation warmer-drier; or cooler-wetter
slide courtesy Inez Fung [I. Fung, S. Doney, et al.]]
Summary
The North American Carbon Program will:
•measure the large sink for fossil fuel CO2 that appears to be operating in the region
•determine why this sink exists, and define the controlling factors (temperature, precipitation, legacies, CO2, nutrients, …) quantitatively.
•enable projections of future trajectories
•support decision makers in dealing with key global change issues through management and policy options.