Climate change

Question 1

what are paleoclimates

Answer 1

climates from ancient times

Question 2

what is a proxy

Answer 2

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

Question 3

give 3 examples of proxies

Answer 3

tree rings, coral rings, ice cores

Question 4

how are corals used as proxies

Answer 4

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

Question 5

how are ice cores used as proxies

Answer 5

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

Question 6

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

Answer 6

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

Question 7

how do lake sediments show past climates

Answer 7

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

Question 8

why can pollen be used as a proxy for climate

Answer 8

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

Question 9

what is isotopic fractionation

Answer 9

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

Question 10

how are isotopes used to measure paleoclimates

Answer 10

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

Question 11

how can isotopes be used to identify glacial ages

Answer 11

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

Question 12

when did temps last begin to cool on earth and why

Answer 12

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

Question 13

how often do ice age cycles take place

Answer 13

every 100,000 years

Question 14

when was the peak of the last ice age?

Answer 14

20,000 years ago

Question 15

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

Answer 15

2km, 400m

Question 16

by how much do temperatures change in an ice age

Answer 16

4-5 degrees

Question 17

give the three elements of the Milankovitch cycles and their frequency

Answer 17

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

Question 18

give an example of a rapid change in a paleoclimate

Answer 18

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

Question 19

how do volcanic eruptions affect climate

Answer 19

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

Question 20

give two examples of volcanoes that impacted world climate

Answer 20

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

Question 21

the 2 external causes of climate change

Answer 21

solar variation and milankovitch cycles

Question 22

the 5 internal causes of climate change (NATURAL)

Answer 22

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

Question 23

how can changes in ocean circulation impact climate

Answer 23

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

Question 24

how can shifting continents impact climate

Answer 24

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

Question 25

what are the negative feedbacks involved in carbon cycle

Answer 25

increased warming -> weathering of silicate rocks->sequestration of CO2-> cooling -> less weathering-> increased warming…

Question 26

give a positive feedback in relation to the carbon cycle

Answer 26

more CO2-> warmer-> more soil respiration-> more CO2 in atmosphere

Question 27

give a positive feedback in relation to the carbon cycle in the ocean

Answer 27

warmer-> ocean absorbs less CO2-> more acidic-> becomes a source not a sink (release hydrocarbons frozen in sediments)

Question 28

name two processes that can potentially cause cooling

Answer 28

deforestation and aerosols increase albedo

Question 29

what is an RCP

Answer 29

representative concentration pathway. its a projected future climate scenario

Question 30

give a brief breakdown of the climate of the last millennium

Answer 30

medieval warm period, colder period and little ice age, advancing glaciers, overall warming trend since mid 19th century

Question 31

when did the last glaciation begin and end

Answer 31

70,000yr ago, ended 10,000 yr ago

Question 32

how can we find out about the extent of the last glaciation

Answer 32

compare snow lines of modern and old glaciers, ancient trees buried in ice sheets can be dated and indicate the rate of ice advancement

Question 33

why did many animals go extinct during glaciation

Answer 33

many animals trapped between large ice sheet to north, and alpine glaciers to the south

Question 34

name the period of time when the dinosaurs were alive

Answer 34

warm middle cretaceous, 100 mil years ago, one of warmest periods in history, with higher sea levels