Paleontological Perspectives on Climate Change Alec Tewsley-Booth 8 February 2012 Purpose • 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 Paleontology • 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 • http://www.youtube.com/watch?v=cQVoSy Vu9rk 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 forests • 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 weathering 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 Extinctions • 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 Pangaea • Single continental mass • Disruption of climate; consider the climate of the Midwest • More to climate than just atmospheric disturbance • Winds and current patterns play a major roll 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 insects • 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 quickly • Antarctic ice sheet begins to form • Evolution of a very modern fauna CO2-Temperature Decoupling • CO2 and temperature are not always correlated • 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 history • 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 changes • 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