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)
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.
Photosynthesis/RespirationCO2 + H20 ↔ CH2O + O2
Weathering/PrecipitationCO2 + CaSiO3 ↔ CaCO3 + SiO2
Long-term Carbon Cycle: rocksTwo generalized reactions…
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
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.
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.