Climate change Flashcards
what are paleoclimates
climates from ancient times
what is a proxy
preserved physical characteristics of the past that allow scientists to reconstruct climatic conditions in the past
give 3 examples of proxies
tree rings, coral rings, ice cores
how are corals used as proxies
produce rings as they grow, chemical composition tells us about climatic conditions. ratio of oxygen 16 to oxygen 18 as corals = calcium carbonate
how are ice cores used as proxies
ratio of oxygen 16 and 18, tiny bubbles of gas trapped in ice
what can be used as a proxy for millions of years into the past
deep sea sediment cores, contain fossils of tiny sea creatures (foraminifera) that preserve a chemical record of past climatic change
how do lake sediments show past climates
annual layers (varves) give a timescale, more eroded sediment from glaciers in summer than winter
why can pollen be used as a proxy for climate
pollen grains are erosion resistant and can show the changes in plant life
what is isotopic fractionation
more O18 in water that falls as precipitation while water in clouds is enriched with O16 (O18 is heavier)
how are isotopes used to measure paleoclimates
many earth materials equilibrate chemically with water and preserve isotopic signature of the surroundings (preserve past temp. as isotopic fractionation is temp dependent)
how can isotopes be used to identify glacial ages
during glacial ages, water with O16 evaporated more easily from ocean to precipitate as glaciers-> more O16 in the ice, more O17 and O18 in the ocean water and marine organisms
when did temps last begin to cool on earth and why
50 mil years ago, removal of CO2 by rainwater and sequestration in the geosphere
how often do ice age cycles take place
every 100,000 years
when was the peak of the last ice age?
20,000 years ago
how much ice lay over Toronto and Dublin at the peak of the ice age
2km, 400m
by how much do temperatures change in an ice age
4-5 degrees
give the three elements of the Milankovitch cycles and their frequency
- eccentricity: shape of earths orbit, 100,000 yrs
- obliquity: angle of tilt of rotational axis, 40,000 years
- precession: direction of the axis, 20,000 years
give an example of a rapid change in a paleoclimate
younger dryas- sudden cooling of the climate after period of warming. re emergence of ice sheets.
how do volcanic eruptions affect climate
aerosols and gases increase albedo (if volcano erupts into the stratosphere in the tropics)
give two examples of volcanoes that impacted world climate
Mt Tambora in 1816- cooled temps by 0.4-0.7 deg. for 2 years
Mt Pinatubo in 1991, temp cooled up to 0.4 deg. for a year
the 2 external causes of climate change
solar variation and milankovitch cycles
the 5 internal causes of climate change (NATURAL)
atmospheric filtering (greenhouse effect), changes in albedo, volcanic CO2, shifting continents, changes in ocean circulation
how can changes in ocean circulation impact climate
fresher/warmer water could disrupt thermohaline circulation, shut down gulf stream, send NA and Europe into a freeze
how can shifting continents impact climate
change paths of ocean currents and wind due to mountain masses. breaking continental masses means different storage of heat, more precipitation etc
what are the negative feedbacks involved in carbon cycle
increased warming -> weathering of silicate rocks->sequestration of CO2-> cooling -> less weathering-> increased warming…
give a positive feedback in relation to the carbon cycle
more CO2-> warmer-> more soil respiration-> more CO2 in atmosphere
give a positive feedback in relation to the carbon cycle in the ocean
warmer-> ocean absorbs less CO2-> more acidic-> becomes a source not a sink (release hydrocarbons frozen in sediments)
name two processes that can potentially cause cooling
deforestation and aerosols increase albedo
what is an RCP
representative concentration pathway. its a projected future climate scenario
give a brief breakdown of the climate of the last millennium
medieval warm period, colder period and little ice age, advancing glaciers, overall warming trend since mid 19th century
when did the last glaciation begin and end
70,000yr ago, ended 10,000 yr ago
how can we find out about the extent of the last glaciation
compare snow lines of modern and old glaciers, ancient trees buried in ice sheets can be dated and indicate the rate of ice advancement
why did many animals go extinct during glaciation
many animals trapped between large ice sheet to north, and alpine glaciers to the south
name the period of time when the dinosaurs were alive
warm middle cretaceous, 100 mil years ago, one of warmest periods in history, with higher sea levels
