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.