FGHALL 1

Greenhouse Gases•Carbon dioxide CO2

•Methane CH4

•Water Vapor H2O•Nitrous Oxide N2O•Chloroflorocarbons CFC’s•Ozone O3

Absorbing Aerosols•Smoke•Soot

Warming: Greenhouse gases Absorbing aerosols

Warming: Greenhouse gases Absorbing aerosols

Clouds

Soot

Greenhouse Gases

Cooling:

Reflective aerosols•CLOUDS•DUST•VOLCANIC AEROSOLS

Natural carbon sequestration•Vegetation/Soils•Air-sea CO2 equilibrium•Ocean Biota

Carbon

Smoke

HeatHeat

∆Earth’s Heat Balance = Warming - Cooling

FGHALL 2

The Global Carbon Cycle

Humans

Atmosphere

+ 3/yr

Ocean Land

~ 92

~120

~122

7 PgC*/yr

~90

Over half the CO2 released by humans is absorbed by oceans and land.

Will this continue?

*PgC = Peta (1015) grams of carbon2 t

o oce

ans 2 to land

FGHALL 3

How will carbon-coupled How will carbon-coupled feedbacks affect future climatefeedbacks affect future climate

ecosystems, and life?ecosystems, and life?

ClimateClimate

LandLand

OceanOcean

How is the How is the earth earth

sequesteringsequesteringcarbon at an carbon at an

increasing increasing rate?rate?

How long can How long can this this

continue?continue?

FGHALL 4‘‘Photosynthesis’Photosynthesis’ by Ursula Freerby Ursula Freer

Biological Biological ProductivityProductivity

Michael Michael BehrenfeldBehrenfeld

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LeafLeaf Photosynthesis Photosynthesis Piers Seller’s PAR DiagramPiers Seller’s PAR Diagram

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Photosynthesis Action SpectrumPhotosynthesis Action Spectrum

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Vegetation indices--future topicVegetation indices--future topic

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FGHALL 9

Satellite Chlorophyll and PhotosynthesisSatellite Chlorophyll and Photosynthesis

Pigment containing chloroplast membranes

CO2 HCO3

-1CO3

-2

= cellular organelles originating through endosymbiosis

FGHALL 10

~50 ~100

FGHALL 11

FGHALL 12

Will SUVs start the next ice age?Will SUVs start the next ice age?

FGHALL 13

FGHALL 14

FGHALL 15

Where the rubber hits the road…

FGHALL 16

Industrial Revolution: wood & Industrial Revolution: wood & fossil fuels fossil fuels

FGHALL 17

Approaching 50 years of CO2 data

FGHALL 18

Interannual CO2 variations

FGHALL 19

Current Uncertainties

Fos

sil F

uels

To

Atm

osp

her

eT

o L

and

/Oce

an

5.5

±0.3

Lan

d us

e 1

.6 ±

0.8

chan

ge

Oce

an

2.0

± 0

.6

Upt

ake

Uni

dent

ifie

d 1

.8 ±

1.5

Si

nk

Current source and sink strengths are uncertain.

Prediction of future climate forcing is therefore uncertain as well. Peta (1015 ) grams of carbon/year

Atm

osph

eric

3.3

± 0

.2C

arbo

n

FGHALL 20

What are the sequestration processes?• Oceans

– Solubility pump– Biological pump

• Land– CO2 Fertilization

– Nutrient fertilization– Forest regrowth, fire suppression, woody encroachment,

etc.– Response to changing climate

NEE

RGPP

FGHALL 21

Uncertain FuturesOcean Flux

-10

-8

-6

-4

-2

0

2

4

6

8

10

1850 1900 1950 2000 2050 2100

Hadley

IPSL

Land Flux

-10

-8

-6

-4

-2

0

2

4

6

8

10

1850 1900 1950 2000 2050 2100

Atmospheric CO2

200

300

400

500

600

700

800

900

1000

1850 1900 1950 2000 2050 2100

Global Mean Temperature

13

14

15

16

17

18

19

20

1850 1900 1950 2000 2050 2100

Different assumptions project dramatically different futures.

Which is correct? How can we know?

FGHALL 22

USGCRP Science Questions

• What has happened to the CO2 that has already been emitted by human activities?

• How do land management and land use, terrestrial ecosystems and ocean dynamics, and other factors affect carbon sources and sinks over time?

• What will be the future atmospheric CO2 concentration resulting from environmental changes, human actions and past and future emissions?

FGHALL 23

Climate Forcing Factors2

1

0

-1

-2

For

cing

Str

engt

h (

Wat

ts/m

2 )

Greenhouse GasesOther

Anthropogenic Forcings

Natural Forcings

Climate Forcings

0.4±0.2

(indirect via O3)-1.1±0.5

Forced Cloud

Changes

Tropo-spheric Aerosols

N2O0.15±0.05

CFCs0.35±0.05

(indirect via O3 and H2O)

Volcanic Aerosols(range of decadal means)

-0.1±0.1

-0.4±0.3

0.7±0.2

1.4±0.2

SunCO2

(0.2-0.5)

CH4

0.3±0.15

Other Tropospheri

c Ozone

(indirect via stratosphericozone)

Land Cover Alter-ations

-0.2±0.2

Estimated climate forcings between 1850 and 2000

Climate warming from 1850 to 2000 resulted from both human activities and natural causes. Carbon dioxide played an important role.

FGHALL 24

What? Me worry?