physical geography > Climate Change > Flashcards

Climate Change Flashcards

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1
Q

What are the direct measurements of climate change?

A
  • temperature using thermometers
  • rainfall/precipitation
  • pressure and wind measurements
  • atmospheric CO2 measurements
  • satellite measurements
  • sea level
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2
Q

How far back can thermometers measure climate change?

A
  • around 150-170 years
  • earlier measurements exist but are unreliable
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3
Q

How far back can precipitation measure climate change?

A
  • 250-300 years
  • global coverage only improved since 1800s
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4
Q

How far back can atmospheric CO2 measurements study the climate change

A

1958 onwards.

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5
Q

What is the maximum amount of time we can go back with direct climate measurements?

A

Around 150 years with somewhat isolated data to a maximum of 300 years for rainfall

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6
Q

What methods can we use to reconstruct past climates?

A
  • pollen
  • ice cores
  • tree rings
  • fossil evidence
  • ocean sediment
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7
Q

What is a climate proxy

A

Indirect measurements which allow scientists to reconstruct past climates

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8
Q

What do tree rings indicate about earths past climate

A

Thick rings indicate period of fertility when there is high rainfall and warm temperatures.
Narrow rings indicate a drier period.
They can be impacted by other factors such as social, temperature and wind

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9
Q

What do ice cores suggest about the past climate

A

It measures the amount of oxygen and hydrogen bubbles in the ice. Lots of bubbles indicate higher atmospheric gases, highlighting climate change

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10
Q

What do marine and lake sediments suggest about earths past climate

A

Ratio of oxygen isotopes can be analysed to determine the ocean temperatures.
Areas with ots of oxygen indicate cold temperature in previous ice ages

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11
Q

What do fossils suggest about past climate

A

Plants and animals need certain conditions to survive

However there are gaps in fossisl

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12
Q

What does fossil pollen tell us about past climate

A

Amount of pollen in given time period indicates the abundance of vegetations.
High amounts of pollen suggest warmer periods

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13
Q

What do corals suggest about earhts past climate

A

Higher concentrations of heavy isotopes highlight warmer ocean temperatures

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14
Q

Which geological time period are we currently in and when did it start

A

Quaternary period
Started 2.6 million years ago

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15
Q

Which geological time period are we in and when did it start

A

Holocene epoch
11,000 years ago

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16
Q

What are the conditions for Earth’s climate?

A

Icehouse (cold global temperatures with lots of polar ice sheets and persistent ice)

green house (warmer temperatures with high atmospheric CO2, no permenant ice at poles)

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17
Q

What conditions are we currently experiencing

A

Icehoues

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18
Q

What climate state are we currently in

A

Interglacial within the icehouse

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19
Q

Why ha Earth experiences long term cooling trend

A

Falling atmospheric gases as volcanic gasss declines and carbon locked in rocks
Plate tectonics moved continents changing ocean circulation
Opening of cooler ocean pathways
Increased albedo

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20
Q

When did antarctica descend into a permenant icehouse state

A

35 million years ago

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21
Q

What factors contributed to antarctica entering an icehouse state

A
  • less solar energy due to plate moving south
  • opening of Drake Passageway meant no warm water currents so antarctica gets cut off
  • declining atmospheric CO2 concentration
  • this caused feedback mechanisms which caused further melting
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22
Q

Steps to Antarctica entering an icehosue state?

A
  1. Moving from a greenhouse to an icehouse
  2. Plate movements
  3. Opening of ocean gateways
  4. Antarctic circumpolar current
  5. Isolation of Antarctica
  6. Reduced solar energy
  7. Increased albedo
  8. Positive feedback enforces cooling
  9. Formation of permenant ice sheets
  10. Long term cooling of antarctic
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23
Q

What has occured in the Quaternary

A
  • growth and retreat of large continental ice sheets
  • climate variability driven largely by Milankovitch cycles
  • significant sea-level fluctuations
  • glacials (100,000 years)
  • inter-glacials (10-15,000 years)
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24
Q

What are the climatic conditions of the holocene

A

Less extreme temperature fluctuations
Few abrupt climate changes

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25
Why is the holocene considered stable but not static
It has small short term changes which help us to understand natural changes
26
What have been the short term cooling or warming of the holocene
6,000 years ago temp was 1-2 higher Medieval warm period Little ice age - temp fell by 1C and europe went into deep freeze
27
when was the last greenhouse state
100 million years ago
28
when was the transition from greenhouse to icehouse earth
35 million years ago
29
when was the beginning of icehouse earth
quaternary period. 2.6 million years ago
30
when was the interglacial state?
holocene 11,700 years ago
31
what is the Palaeocene - Ecoene thermal maximum (PETM)
- spike in average global temperatures to around 23C when Pangea was splitting - huge amounts of gases were released - globe warmed by 5-9 C - provides a natural case study of rapid global change drive by carbon release
32
what are the types of natural forcing affecting climate change
Milankovitch cycles Volcanic activity Plate tectonics and continental drift Changing ocean currents Natural greenhouse gases Solar output
33
how do Milankovitch cycles affects earths climate
They alter the amount and distribution of solar energy reaching Earth. Drives long term glacial and interglacial periods
34
what are the Milankovitch cycles?
- orbital eccentricity - obliquity - precession
35
what is orbital eccentricity
- the earths orbit around the sun - changes distance the suns' radiation has to travel to reach earth - 30% difference in solar radiation when earth is closest to the sun or furthest away - ice ages occur when it is at its maximum orbital eccentricity
36
what is obliquity
- tilt of earth - when tilt is closer to 22, seasonal differences are reduced and increased solar radiation differences - means snow and ice dont melt during summer, leading to positive feedback
37
what is precession
- wobble of earth -changes in this impact the intensity of seasons - if earth is cloest to sun during winter in north, winters will be warmer
38
what is periphelion
when earth is closest to the sun
39
what is aphelion
when earth is furthest from the sun
40
explain how Milankovitch cycles cause glacial and interglacial periods?
they alter the northern hemisphere summer insolaion, influencing whether ice sheets grow or melt over tens of thousands of years
41
what is the timescale of eccentricity
every 100,000 years
42
what is the timescale of obliquity
every 40,000 years
43
what is the timescale of precession
every 26,000 years
44
what obliquity is required for glacial conditions
low tilt 22 degrees
45
what obliquity is required for interglacial conditions
high tilt 24.5 degrees
46
what precession is required for glacial conditions
summer occurs when earth is farther from the sun in the northern hemisphere
47
what precession is required for interglacial conditions
summer occurs when earth is closer to the sun in the norther hemisphere
48
what eccentricity is required for glacial conditions
more circular orbit causing weak seasonal contrast
49
what eccentricity is required for interglacial conditions
more elliptical orbit causing strong seasonal contrast
50
how does volcanic activiyt act as natural forcing for climate change
- it can cool the climate in the short term by releasing aerosols that reflect solar radiation - over long timescales it warms the climate by adding CO2 through outgassing
51
how does volcanic activity cool the climate in the short timescales
- large explosive eruptions release ash and sulphur dioxide into the atmosphere - SO2 forms sulphate aerosols which reflect incoming radiation -reduces amount of energy reaching earths surface, causing temporary global cooling - after major eruptions, global temperatures can fall for a few years
52
how does volcanic activity cause long term warming of the climate
- volcanic activity releases carbon dioxide into the atmosphere - over timescales, sustained outgassing can increase atmospheric CO2 - this strengthens the greenhouse effect, contributing long term warming and greenhouse conditions
53
what does the hockey stick graph demonstrate about climate change
the hockey stick graph demonstrates that while climate has varied naturally in the past, recent warning is different in rate and is strongly linked to human activity.
54
what is the feedback loop for climate change due to plate tectonics
- plate tectonics drive: - continents move to higher latitude - temperature falls - ice sheet expands - albedo increases - more solar reflected - more ice forms - positive feedback
54
how does plate tectonics and continental drift impact climate change
it impacts where the incoming and outgoing solar radiation hits. this amplifies the feedback loops due to albedo
55
56
how does changing ocean currents impact climate change
intensify or block off warm or cold streams from reaching areas of land eg antarctica
57
how does natural greenhouse gases impact climate
there is a strong link between atmospheric co2 and global temperature. icehouse has less co2 and greenhouse has more
58
what are the main factors responsible for the changes in greenhouse gases
volcanic outgassing. plate tectonics. chemical weathering of rock. ocean atmospheric exchange. biosphere changes. carbon burial and release
59
how does solar outputs such as sun spots impact climate change
areas will get more or less solar energy driving changes in ice sheets and albedo
60
why can changes in solar output not fully explain recent global warming
changes are relatively small and therefore can’t fully explain the magnitude or rate of recent changes. too small to cause high magnitude changes of current day
61
what is the evidence that the world has warmed since late 19 century
- temperature - valley glaciers and ice sheets - rising sea levels - increasing atmospheric water vapour - decreasing snow cover and sea ice - extreme events
physical geography
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