Paleontological Perspectives on Climate Change

Paleontological Perspectives
on Climate Change
Alec Tewsley-Booth
8 February 2012
• Take all claims of “catastrophic climate
change” with a grain of salt
• How much the Earth and its climate have
changed in the last 500 million years
• Give context to discussions about change
on the geologic scale
• Convince you that humans will not cause
the end of the world (any time soon)
How Biology Informs Physics
How Biology Informs Physics
Physics predicts…
Biology tells us…
The Earth’s rotation is slowing down,
lengthening the day.
The Earth’s day used to be shorter (i.e.
400 days/yr in Devonian), known from
growth rings of coral.
The continents shift by rafting as tectonic
plates on the mantle.
Where the continents used to be by
matching fossils across continents.
Rock strata can be used to date geological
events (i.e. Chicxulub impact)
Rock strata can be correlated over
distances by using biostratigraphy
Different isotopes impart different kinetic
properties to molecules
Organic processes preferentially occur on
molecules with one isotope over another
• Not just the study of bones of really big,
really cool dead things
• Applied form of biology and geology
• Interested in extracting information about
ancient life and the environment
• REALLY hard to do
– Imagine trying to do physics with only 100
data points, and someone buried them first!
Prehistoric CO2 Measurements
Isotope analysis
Ice cores
Stomatal index
We often have to find proxies for
atmospheric CO2, which is why there is so
much uncertainty in measurements – this
is one of the curses of paleontology
Phanerozoic CO2
Phanerozoic Temperature
Geologic Time
Continental Drift
Cambrian (540-490 mya)
CO2 ~ 4500 ppm, 16x pre-Industrial
O2 ~ 12.5% by volume, 63% of present
Temp ~ 21°, 7° above present
Sea level 30-90m above present
No ice cover
No terrestrial life
Cambrian Explosion
• Quick radiation from “Ediacaran” fauna
• All modern phyla evolve at this time
• Rapid evolution probably driven by
evolution of predators
• Many ecological niches open up
Devonian (415-360 mya)
CO2 ~ 2200 ppm, 8x pre-Industrial
O2 ~ 15% by volume, 75% of present
Temp ~ 20°, 6° above present
Sea level 180-120m above present
Land has some plants and animals
Carboniferous (360-300 mya)
CO2 ~ 800 ppm, 3x pre-Industrial
O2 ~ 32.5% by volume, 163% of present
Temp ~ 14°, 0° above present
Sea level 120-0-80m above present
Land is dominated by coal swamps and
• Some ice cover
Carbon Burial
• Carbon is taken from atmosphere by
plants, and turned into organic compounds
• Plants can decompose, releasing carbon
back to atmosphere, or be buried  coal
• Other carbon sinks exist, such as oil (from
plankton) and carbonate shells
• Complexity of carbon cycle! – trees and
Permian (300-250 mya)
CO2 ~ 900 ppm, 3x pre-Industrial
O2 ~ 23% by volume, 115% of present
Temp ~ 16°, 2° above present
Sea level 60m above - 20m below present
Worst extinction event in Earth’s history
– 95% of species disappeared
• Formation of Pangaea upsets cimate
• Generally broken into mass extinctions
and background extinctions
• Five universally acknowledged mass
extinctions (O-S, Late D, P-Tr, Tr-J, K-T)
• Defined by a large drop in diversity
• Caused by increased extinction rate or
reduced origination rates
Triassic (250-200 mya)
CO2 ~ 1750 ppm, 6x pre-Industrial
O2 ~ 16% by volume, 80% of present
Temp ~ 17°, 3° above present
Sea levels very low
Desert conditions prevail, leads to success
of reptiles
• Late Triassic – emergence of dinosaurs
• Single continental mass
• Disruption of climate; consider the climate
of the Midwest
• More to climate than just atmospheric
• Winds and current patterns play a major
Jurassic (200-145 mya)
CO2 ~ 1950 ppm, 7x pre-Industrial
O2 ~ 26% by volume, 130% of present
Temp ~ 16.5°, 3° above present
CO2 maximum, yet have largest terrestrial
animals ever
• Landscape dominated by coniferous
forests and fern plains
Cretaceous (145-65 mya)
CO2 ~ 1700 ppm, 6x pre-Industrial
O2 ~ 30% by volume, 150% of present
Temp ~ 18°, 4° above present
By end of Cretaceous CO2 levels are
approaching Cenozoic levels
• Emergence of flowers and associated
• Diversification of mammals
Eocene (55-35 mya)
CO2 ~ 385 ppm, 1.5x pre-Industrial
O2 ~ 20% by volume, 100% of present
Temp ~ 19°, 5° above present
Paleocene-Eocene Thermal Maximum
End of Eocene marked beginning of
icehouse climate
Miocene (25-5 mya)
CO2 ~ 250 ppm, 1x pre-Industrial
O2 ~ 20% by volume, 100% of present
Temp ~ 21°, 7° above present
Began very warm, but began cooling
• Antarctic ice sheet begins to form
• Evolution of a very modern fauna
CO2-Temperature Decoupling
• CO2 and temperature are not always
• Decrease in CO2 at end of Mesozoic did
not follow usher in drastic cooling, climate
remained tropical
• Miocene is another good example of high
temperatures with relatively low CO2
Pleistocene (2.5 mya-11,000 ya)
CO2 ~ 250 ppm, 1x pre-Industrial
O2 ~ 20% by volume, 100% of present
Temp ~ 7°, 7° below present
Widely known because of the large
number of ice ages
• First appearance of modern humans
Ice Ages
• Characterized by glaciation and expanded
ice caps
• Not necessarily caused by extreme
winters, much more common to have
normal winters and cool summers, which
prevent melting
• Ice ages more common in the Cenozoic,
likely linked with CO2 and land masses
Holocene (11,000 ya-present)
CO2 ~ 250ppm pre-Industrial to 350ppm
O2 ~ 20% by volume
Temp ~ 14°
Marked by beginning of modern human
• VERY short compared to other periods
Present Mass Extinction
• Debate whether or not we are in a sixth
mass extinction
• Hard to determine, because extinction
events are normally studied over millions
of years, not centuries
• Ice age extinction of megafauna – some
links to human radiation
 people have been screwing things up
since BEFORE CO2 was a concern
Where Humans Come In
• Australopithecus appeared ~4 mya
• Homo genus had evolved by about 2 mya
• Both clades evolved in warm (comparable
to present) conditions in Africa
• Only three species, H. neanderthalensis
(Denisovans too?), H. floresiensis and H.
sapiens survived into last ice age
• Only H. sapiens truly came out of ice age
The Future
• The Eath goes through cycles in both gas
levels and temperature, which are not
necessarily correlated (Miocene decoupling)
• All species must adapt to environmental
• CO2 levels aren’t dangerous, but if they
change too fast, evolution may not keep up
• Humans have the power to change the
climate, but not control it – care is needed
Thanks to…
Professor Budker
Professor Kevin Padian
Professor Charles Marshall
Professor Tony Barnosky
Professor Jim McGuire

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