Detecting Past Climates

Taking measurements Only recorded over last 150-200 years Proxy data- reconstruct data using indirect evidence (ex: seafloor sediment, ice core samples, tree rings etc.) Paleoclimatology: study of ancient climates

Seafloor sediment Surface organisms, die, sink become part of seafloor sediment What we know: Certain organisms thrive in certain climates Deeper the dig, farther back in time

Oxygen isotope analysis Two oxygen isotope: O16 and O18; both are part of water molecules, O16 is lighter and more abundant Water with O16 evaporates more easily, thus more in O18 ocean water and more O16 in glacial ice during cold/glacial periods. More O16 in ocean water during warm periods Thus, when organisms use water when making shells, if there’s more O18 the climate was warmer, more O16 the climate was cooler

Isotopically light means the ratio favors O16 Nonglacial (warm) period- more O16 evaporates, then rains and returns; so MORE O16 to O18 in ocean. Glacial (cool) period- evaporation but O16 doesn’t return, stay in glacier, so MORE O18 in ocean

Constructed Temperature based on sea sediment layers and oxygen isotope analysis of organisms in the sediment

Glacial Ice cores Drill in glaciers (poles, mountains, etc) for core of ice Within ice, bubbles of air (ancient atmosphere) Deeper the drill farther back in time (approximately 200,000 years back) Cores also include dust, pollen, ash, etc, deposited on the ice Use oxygen isotope to determine past temp More O16 locked in the ice, cooler temp.

Dendrochronology Tree rings- one ring = one year Wide ring = large growth (good conditions for that species) Use size/thickness of rings to infer precipitation and temperature Useful up to about 1000 years for past climates

Other proxy data Fossilized plant pollen: biological activity gives clues to climate conditions Coral reef: coral make limestone (CaCO3) so can use oxygen isotope analysis to examine climate conditions) Historical data: manuscripts, novels, historical records, art