Oceanic COOceanic CO22 removal options: removal options:

Potential impacts and side effects Potential impacts and side effects

Andreas Oschlies

IFM-GEOMAR, Kiel

The Problem The Problem (?)(?)The Problem The Problem (?)(?)

Global Warming

(GISTEMP, Hansen et al., 2009)

Possible/likely risksPossible/likely risksPossible/likely risksPossible/likely risks

Individual attribution to global warming difficult

The cause: Anthropogenic CO2The cause: Anthropogenic CO2

Atmospheric CO2 concentration rises (only about half as fast as emissions!)

Charles Keeling (1928-2005)

Risk assessment IPCC ScenariosRisk assessment IPCC Scenarios

(IPCC, AR4, 2007)

IPCC Scenarios & RealityIPCC Scenarios & Reality

(Manning et al., 2010)

Projected global warmingProjected global warming

(Meinshausen et al., 2009)

Challenge: halving global emissions by 2050Challenge: halving global emissions by 2050

• reduce global emission by factor 2

• population growth by factor 2

• energy consumption at current EU-niveau: factor 5

• required reduction in individual emissions: 2 x 2 x 5 = 20

• Reaching this by transition to carbon-neutral power sources requires installation of ~1GW/day (until 2050).

(perhaps not impossible, but VERY challenging: in 2009 Germany installed ~5GW/yr, close to required 10GW/yr)

OptionsOptions

Anthropogenic impact on the

climate system

MitigationReducing emissions

requires collaboration

OptionsOptions

Anthropogenic impact on the

climate system

Common welfare

MitigationReducing emissions

Adaptation

requires collaboration perception of costs

OptionsOptions

Anthropogenic impact on the

climate system

Climate system Common welfare

MitigationReducing emissions

Climate Engineering

Adaptation

requires collaboration perception of costsunilateral option?

Climate EngineeringClimate Engineering

(Keith, 2001)

“Solar Radiation Management”“Solar Radiation Management”Atmospheric CO2 lifetime is long

(Archer et al., 2009)

No short-term SRM solution without CO2-sequestration

CO2-Rest von 1000 GtC

“Solar Radiation Management”“Solar Radiation Management”

(Archer et al., 2009)

CO2-Rest von 5000 GtC

Atmospheric CO2 lifetime is long

No short-term SRM solution without CO2-sequestration

CO2CO2

alkalinityenhancement

afforestation

storage reservoirs

direct injection

Fe fertilization

artificial upwelling

artif.trees

CO2

CO2

CO2

CO2-SequestrationCO2-Sequestration

(Oschlies, 2010)

CO2CO2

alkalinityenhancement

afforestation

storage reservoirs

direct injection

Fe fertilization

artificial upwelling

artif.trees

CO2

CO2

CO2

CO2-SequestrationCO2-Sequestration

(Oschlies, 2010)

AfforestationAfforestation

Culturally often viewed “positively”

Limited potential (space)•Restricted to growth phase•Afforesting Australia ~10% of current emissions for ~100yr

Impacts ecosystems

Competes with food production

AfforestationAfforestation

Forests generally darker than crop land•Particularly at high/mid latitudes in winter•Net warming or cooling?

CO2CO2

alkalinityenhancement

afforestation

storage reservoirs

direct injection

Fe fertilization

artificial upwelling

artif.trees

CO2

CO2

CO2

CO2-SequestrationCO2-Sequestration

(Oschlies, 2010)

“artificial trees”“artificial trees”

expensive (300 $ /ton CO2?),

Energy intensive (net CO2-sink?)

Still requires storage of CO2(courtesy David Keith)

(courtesy Klaus Lackner)

CO2CO2

alkalinityenhancement

afforestation

storage reservoirs

direct injection

Fe fertilization

artificial upwelling

artif.trees

CO2

CO2

CO2

CO2-SequestrationCO2-Sequestration

(Oschlies, 2010)

Lack of fertilization?Lack of fertilization?

Present-day sea-surface nitrate concentrationsmmol/m3

Mean profile

(Conkright et al., 1994)

lack of macronutrients(e.g., NO3, PO4, Si(OH)4)

lack of micronutrients(e.g., Fe)

Ocean fertilisationOcean fertilisation

Macronutrients (NH4, NO3, PO4)

• need 140kg NH4 to fix 1t C (+70kg PO4)

• Input from land, e.g. Ocean NourishmentTM

• Artificial upwelling, e.g. AtmOcean

Micronutrients (Fe)• need 10-1000g Fe to fix 1t C (Planktos, Climos)

CO2CO2

alkalinityenhancement

afforestation

storage reservoirs

direct injection

Fe fertilization

artificial upwelling

artif.trees

CO2

CO2

CO2

CO2-SequestrationCO2-Sequestration

(Oschlies, 2010)

Artificial upwellingArtificial upwelling

Sea surface

Z(mix)

CO2, O2

organic matterinorganic nutrientsnutrients, CO2

z

pumping by surface wave-driven valves

Simulated artificial upwellingSimulated artificial upwelling

potential pCO2 (in ppm) for pipes up to 1000m deep.Mean: -18ppm(might get more negative/better with time!)

Simulated artificial upwellingSimulated artificial upwelling

potential pCO2 (in ppm) for pipes up to 1000m deep.Mean: -18ppm(might get more negative/better with time!)

Potential: about 80 GtC over 100 years (~10% of current emissions)

BUT: Small oceanic contribtion!

(Oschlies et al., 2010)

Side effect 1: Where is the missing C?Side effect 1: Where is the missing C?In the soils!

Coc

Cter Csoil

SAT

kgC/m2

Side effect 2: “irreversibility”Side effect 2: “irreversibility”

(Oschlies et al., 2010)

Whenever ocean upwelling is stopped, mean temperatures soon exceed those of a world without Climate Engineering.

Earth’s radiation balance:

Planet with colder surface waters stores more energy

CO2CO2

alkalinityenhancement

afforestation

storage reservoirs

direct injection

Fe fertilization

artificial upwelling

artif.trees

CO2

CO2

CO2

CO2-SequestrationCO2-Sequestration

(Oschlies, 2010)

Ocean Iron FertilizationOcean Iron Fertilization

Present-day sea-surface nitrate concentrationsmmol/m3

Mean profile

(Conkright et al., 1994)

lack of micronutrients

Iron Fertilization at SeaIron Fertilization at Sea

“Give me a tanker load of iron and I will give you the next ice age”

(John Martin, early 1990s)

(John Martin, early 1990s)

“Give me a tanker load of iron and I will give you the next ice age”

Iron Fertilization at SeaIron Fertilization at Sea

SERIES, 2002

SOIREE, 1999+ 400 kg Fe

removed~ 400 t C

Natural Southern Ocean Fe fertilization: Crozet Islands

Natural Southern Ocean Fe fertilization: Crozet Islands

(Pollard et al., 2009)

Simulated Southern Ocean Fe fertilizationSimulated Southern Ocean Fe fertilization

fertilized areaglobal

Potential: 60 GtC over 100 years

Global uptake < local CO2 flux

non-local backflux

(Oschlies et al., 2010)

Possible side effect: SuboxiaPossible side effect: Suboxia

OIF-induced decrease in simulated suboxic volume!

Possible side effect: AcidificationPossible side effect: Acidification

Reduced acidification in remote surface waters!

pH

More (serious?) side effects: N2O, ecologyMore (serious?) side effects: N2O, ecology

Jin & Gruber (2003): offsetting effect of enhanced N2O emissions: ca 5-20%

Ecological effects poorly understood

•Ecological effects intended

•Will have winners and losers

CO2CO2

alkalinityenhancement

afforestation

storage reservoirs

direct injection

Fe fertilization

artificial upwelling

artif.trees

CO2

CO2

CO2

CO2-SequestrationCO2-Sequestration

(Oschlies, 2010)

Dissolution of carbonate and silicate rocksDissolution of carbonate and silicate rocksAlkalinity enhancement = neutralizes carbonic acid

Reduces pCO2 of surface water enhances air-sea CO2 flux

Major mining operation!

Limited by ocean circulation to <1GtC/yr sequestration (to avoid oversaturation; Köhler et al., 2010)

Contamination by trace metals likely.

CO2CO2

alkalinityenhancement

afforestation

storage reservoirs

direct injection

Fe fertilization

artificial upwelling

artif.trees

CO2

CO2

CO2

CO2-SequestrationCO2-Sequestration

(Oschlies, 2010)

Direct CO2 injection into the oceanDirect CO2 injection into the ocean

Currently not allowed (London “Anti-dumping” convention & protocol)

Direct CO2 injection into the oceanDirect CO2 injection into the ocean

According to 3D ocean circulation models, deep injection has life times of hundreds of years.

(Orr et al., 2001)

ConclusionsConclusions Sequestration potential of all methods limited to about

1GtC/yr over 100 years, each. • Artificial upwelling: messes up Earth’s radiation balance

• Fe fertilization: messes up ecosystem, but has natural analogs

• Alkalinity enhancement: major mining operation, impurities

Direct injection has large potential but is currently considered as dumping.

Validation? • Not locally possible (if at all)