Climate change Flashcards

1
Q

what are paleoclimates

A

climates from ancient times

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2
Q

what is a proxy

A

preserved physical characteristics of the past that allow scientists to reconstruct climatic conditions in the past

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3
Q

give 3 examples of proxies

A

tree rings, coral rings, ice cores

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4
Q

how are corals used as proxies

A

produce rings as they grow, chemical composition tells us about climatic conditions. ratio of oxygen 16 to oxygen 18 as corals = calcium carbonate

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5
Q

how are ice cores used as proxies

A

ratio of oxygen 16 and 18, tiny bubbles of gas trapped in ice

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6
Q

what can be used as a proxy for millions of years into the past

A

deep sea sediment cores, contain fossils of tiny sea creatures (foraminifera) that preserve a chemical record of past climatic change

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7
Q

how do lake sediments show past climates

A

annual layers (varves) give a timescale, more eroded sediment from glaciers in summer than winter

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8
Q

why can pollen be used as a proxy for climate

A

pollen grains are erosion resistant and can show the changes in plant life

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9
Q

what is isotopic fractionation

A

more O18 in water that falls as precipitation while water in clouds is enriched with O16 (O18 is heavier)

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10
Q

how are isotopes used to measure paleoclimates

A

many earth materials equilibrate chemically with water and preserve isotopic signature of the surroundings (preserve past temp. as isotopic fractionation is temp dependent)

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11
Q

how can isotopes be used to identify glacial ages

A

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

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12
Q

when did temps last begin to cool on earth and why

A

50 mil years ago, removal of CO2 by rainwater and sequestration in the geosphere

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13
Q

how often do ice age cycles take place

A

every 100,000 years

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14
Q

when was the peak of the last ice age?

A

20,000 years ago

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15
Q

how much ice lay over Toronto and Dublin at the peak of the ice age

A

2km, 400m

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16
Q

by how much do temperatures change in an ice age

A

4-5 degrees

17
Q

give the three elements of the Milankovitch cycles and their frequency

A
  1. eccentricity: shape of earths orbit, 100,000 yrs
  2. obliquity: angle of tilt of rotational axis, 40,000 years
  3. precession: direction of the axis, 20,000 years
18
Q

give an example of a rapid change in a paleoclimate

A

younger dryas- sudden cooling of the climate after period of warming. re emergence of ice sheets.

19
Q

how do volcanic eruptions affect climate

A

aerosols and gases increase albedo (if volcano erupts into the stratosphere in the tropics)

20
Q

give two examples of volcanoes that impacted world climate

A

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

21
Q

the 2 external causes of climate change

A

solar variation and milankovitch cycles

22
Q

the 5 internal causes of climate change (NATURAL)

A

atmospheric filtering (greenhouse effect), changes in albedo, volcanic CO2, shifting continents, changes in ocean circulation

23
Q

how can changes in ocean circulation impact climate

A

fresher/warmer water could disrupt thermohaline circulation, shut down gulf stream, send NA and Europe into a freeze

24
Q

how can shifting continents impact climate

A

change paths of ocean currents and wind due to mountain masses. breaking continental masses means different storage of heat, more precipitation etc

25
what are the negative feedbacks involved in carbon cycle
increased warming -> weathering of silicate rocks->sequestration of CO2-> cooling -> less weathering-> increased warming...
26
give a positive feedback in relation to the carbon cycle
more CO2-> warmer-> more soil respiration-> more CO2 in atmosphere
27
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)
28
name two processes that can potentially cause cooling
deforestation and aerosols increase albedo
29
what is an RCP
representative concentration pathway. its a projected future climate scenario
30
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
31
when did the last glaciation begin and end
70,000yr ago, ended 10,000 yr ago
32
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
33
why did many animals go extinct during glaciation
many animals trapped between large ice sheet to north, and alpine glaciers to the south
34
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