Evidence for Climate Variation Flashcards
What are some examples of ancient evidence of climate variation
- In the rock. Lasting 100s of millions of years
- Fossils and microfossils
- Pollen grains in sedimentary rocks
- Changes in rock types
- Changing isotope ratios in rocks and deep sea sediments
What are some examples of recent evidence of climate variation
- In more destructible mediums, lasting up to a few million years
- Ice cores containing gas bubbles and oxygen isotopes
- Isotope ratios shown in stalagmites, stalactites and corals
- Dendrochronology
- Aboriginal art sites showing now-extinct species and environments
- Human instrumental records
How can fossils be used to determine ancient climate conditions?
- Terrestrial animals (size, diet, tooth chemistry)
- Plant fossils
- Coral reefs (locations of inland reeds, sea level changes, climate of the area - coral requirements)
- Foraminifera (found only in certain environments such as warm water or shallow tidal areas)
How can pollen grains be used to determine ancient climate conditions
By reconstructing vegetation history (e.g. forest vs arid-adapted taxa)
How do changes in rock time provide evidence of climate variation
- Coal indicates wet climate conditions for fossilisation
- Coal deposits in Antarctica indicate that the climate was wet at some point in the past
- Dropstones (from glacier melt) indicate past cool dry climate conditions by showing glacial action
- Evaporate indicates warm and dry climate conditions as shallow oceans evaporate and do not refill with water, start of a warm period
How do changing Isotope Ratios in Deep Sea Sediments provide evidence for ancient climate variation?
In cold climates, mostly regular water is evaporated (not enough energy to evaporate heavy water), more regular water is in glaciers than in the ocean. More heavy water in the ocean, which is found in the carbonate shells of animals
In cooler temperatures, there is more O-18 in the ocean and O-16 is trapped in glaciers whereas, in warm temperatures, there is less O-18 and O-16 melts back into the ocean
How do gas bubbles in ice cores indicate changes in more recent climate change?
Ice cores are drawn containing volcanic ash, gas bubbles, and other evidence
Gas bubbles are direct examples of the composition of the atmosphere at the time (also contain O-18)
How do coral core samples indicate changes in more recent climate conditions?
In warmer conditions, there are lower concentrations of O-18 in corals since they absorb this oxygen from the ocean and vice versa
How do isotope ratios in speleothem samples indicate changes in more recent climate conditions?
They indicate increases and decreases in temperature
How is dendrochronology used to indicate changes in more recent climate conditions?
The thickness of rings can determine sudden climate events and variations in climate
How can Aboriginal art sites indicate changes in more recent climate conditions?
- The art sites must actually depict megafauna - Unreliable depending on the site
- The art sites must be dated so that we can make conclusions about when the climate changes - High reliability, with techniques becoming more refined and reliable with technological advancements
- The decline or extinction of megafauna must be attributable to climate change - Moderate reliability with more evidence leaning towards climate change
How can human instrumental records indicate changes in more recent climate conditions?
- Using technology (thermometers, etc.) to record qualitative data
- Keeping this data for future use
- Analysing the collected data after sufficient time
A limitation of human instrumental records is that data has only been recorded since the mid 19th century. It is the most reliable and valid data; however, it also has the most limited range
