Ian M. MillerCurator of Paleontology

DMNSWIPS March Meeting, 2008

Plankton, and Plants,

and Tectonics!

Oh My!The role of the long-term carbon cycle in

Earth’s climate.

Earth’s Climate The average of weather and the combination of…

Solar Energy (distance from the Sun, intensity)

Atmosphere (composition & currents)

Oceans (composition, currents, & geology)

Ice (extent on land and sea)

Continents (location, elevation, & geology)

Plants & Animals (on land & in the seas)

Climate ChangeAt four (or five) time scales…

Modern time:Anthropocene (last ~200 yrs—industrialization)

Holocene (last ~10,000 yrs—human civilization)

Deep Time:Pleistocene (last ~1.8 million yrs—icehouse)

Previous 4.5 by (almost always a greenhouse)

Phanerozoic (542 Ma to ~10 Ka)

Climate ChangeAt three scales of climatic cycles…

Geologic:Long-term carbon cycle (millions of yrs)

Milankovitch:Earth’s orbital dynamics (400,000, 100,000, 40,000, and 20,000 Ka)

Sub-Milankovitch: (amplify longer cycles)

Short-term carbon cycle (~100’s to 1,000’s yrs)Solar/Sunspot cycles (~10’s to ~1000’s yrs) Climatic oscillations (2-7 yrs: El Nino La Nina)

Climate Oscillations:

SouthAmerica

Climate Oscillations: During “Normal Years” or La Nina

Warm water in the western Pacific causes low pressure and high rainfall;pressure system drives tradewinds from east to west;tradewinds drive warm water to the west;causing cold water to rise off South America and flow west.

SouthAmerica

Climate Oscillations:During “El Nino”

Warm water shift to the eastern Pacific causes drought in western Pacific;low pressure over the warm eastern Pacific causes heavy rainsand inhibits upwelling along the coast of South America.

The Ice Record: Milankovitch

Orbital Eccentricity (~100,000 yr cycle)

Orbital Tilt (~41,000 yr cycle)

Orbital Precession (~23,000 yr cycle)

The Ice Record: Milankovitch

Brook, 2008 Nature

The Ice Record: Milankovitch

Carbon THE greenhouse gas

Brook, 2008 Nature

The Ice Record: Milankovitch

Short-term carbon cycle: ~10’s to 1000’s of years

Photosynthesis:CO2 + H2O + light energy → CH2O + O2

Respiration:CH2O + O2 → CO2 + H2O + energy

Icehouse Earth

Sea Ice

Continental Ice at the poles

Green River Fm: Greenhouse World

Courtesy K. Johnson

Courtesy K. Johnson

Fossil Lotus

Courtesy K. Johnson

Living LotusCourtesy K. Johnson

Lowland rainforest, Panama

Lomonosov Ridge

Azolla (floating fern)

The Arctic Sea 50 million years ago

Courtesy K. Johnson

Royer et al., 2003

Geologic cycles: Climate through

the Phanero-

zoic—carbon is the culprit

Photosynthesis/RespirationCO2 + H20 ↔ CH2O + O2

Weathering/PrecipitationCO2 + CaSiO3 ↔ CaCO3 + SiO2

Long-term Carbon Cycle: rocksTwo generalized reactions…

Berner, 2001

Long-term carbon cycle: rocks

A Carbon Thermostat• Fluxes in and out of the major reservoirs

are relatively constant leading to an equilibrium in atmospheric CO2—there are negligible changes in fluxes during the Pleistocene.

A Carbon Thermostat• Fluxes in and out of the major reservoirs

are relatively constant leading to an equilibrium in atmospheric CO2—there are negligible changes in fluxes during the Pleistocene.

• In geologic time, negative feedbacks serve to regulate the equilibrium.– High CO2, more warming, more plant growth,

less CO2, less warming…

No sinks: Runaway Greenhouse Effect

• 97% carbon dioxide• 3% nitrogen• Water & sulfuric acid

clouds• Temperature:

>800°F – more than twice as hot as Mercury

Venus

No sources:Snowball

Earth

~650 Ma

Berner, 2001

Long-term carbon cycle: sinks

Photosynthesis (sink):CO2 + H2O + light energy → CH2O + O2

Swamp Forests of the Paleozoic

Photosynthesis (sink):CO2 + H2O + light energy →

CH2O + O2

Weathering (sink):CO2 + CaSiO3 → CaCO3 + SiO2

Precipitation (sink):CO2 + CaSiO3 → CaCO3 + SiO2

Precipitation (sink):CO2 + CaSiO3 → CaCO3 + SiO2

Berner, 2001

Long-term carbon cycle: sources

Georespiration (oxidation, source):CH2O + O2 → CO2 + H2O

Georespiration (thermal decomposition):CH2O + O2 → CO2 + H2O

Georespiration (thermal decomposition):CH2O + O2 → CO2 + H2O

Georespiration (mantle source):CH2O + O2 → CO2 + H2O

Berner, 2001

Long-term carbon cycle: sources and sinks

How do long-term carbon flux changes alter the climate?

• The ice age and the oxygen maximum during the Late Carboniferous.

• Draw down of CO2 leading up to the Pleistocene minimum.

Royer et al., 2003

Climate and

Carbon through

the Phanero-

zoic.

Paleozoic Swamp Forests

Berner, 2003

CO2 and O2 through the Phanerozoic

Extant Dragonfly

Permian Dragonfly

Royer et al., 2003

Climate and

Carbon through

the Phanero-

zoic.

Subduction (source) then Weathering (sink)

Subduction then UpliftCenozoic Deep Sea Climate Record

Time, Ma

Brook, 2008 Nature

The Ice Record

IPCC 2001 Temperature Curve

Georespiration (thermal decomposition):CH2O + O2 → CO2 + H2O

Berner, 2001

>100 times faster than volcanoes

1946 – 1950

svs.gsfc.nasa.gov

1956 - 1960Temperature

svs.gsfc.nasa.gov

1966 - 1970Temperature

svs.gsfc.nasa.gov

1976 - 1980Temperature

svs.gsfc.nasa.gov

1986 - 1990Temperature

svs.gsfc.nasa.gov

1996 - 2000Temperature

svs.gsfc.nasa.gov

2002 - 2006Temperature

svs.gsfc.nasa.gov

Minimum Sea Ice 1979September, 1979

Minimum Sea Ice 2005September, 2005

September, 2007

The Long-term carbon cycle and Earths climate:

Carbon cycles:Long-term carbon cycle (millions of yrs)

Driver of long-term climate changesResponsible for Icehouses/Greenhouses

Short-term carbon cycle (~100’s to 1,000’s yrs)May exacerbate short-lived climate events

e.g. Milankovitch cyclesDoesn’t play a role in long-term climate

Long-term carbon cycle and today:Burning fossil fuels is like setting off volcanoes >100 times

faster than present eruptions ratesRunning a global experiment, which in not analogous to

glacial-interglacials.