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Paleoclimate > L8 - The Hockey Stick > Flashcards

L8 - The Hockey Stick Flashcards

1
Q

What 3 things need to be considered for climate change over the past millennium?

A
  1. Are there similarities across the globe?
  2. Is there evidence for millennial and orbital variability?
  3. Is 20th century warming due to natural or anthropogenic causes?
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2
Q

When was the little ice age and how much cooling was there?

A

1500s/1600s

0.5 Deg C

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3
Q

What 2 changes have there been in the last century?

A
  1. Global retreat of glaciers

2. The Hockey Stick!

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4
Q

What are the 5 main archives for looking at climate change in the last 1000 years?

A
  1. Polar Ice Cores
  2. Mountain Ice Cores
  3. Tree Ring Records
  4. Corals
  5. Marine Sediments
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5
Q

Give 5 pre-industrial records

A
  1. Anecdotal written accounts
  2. Ships Log
  3. Drawings
  4. Photographs
  5. Written descriptions
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6
Q

Give 5 problems with instrumentation that aren’t climatic influences

A
  1. Changes in instrument station location
  2. Changes in observation times
  3. Changes in instrumentation
  4. Changes in the observation environment
  5. Calibration Requirements
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7
Q

When were mercury thermometers invented?

A

17th C

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8
Q

When did the temperature record in Central England begin?

A

1659

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9
Q

Since when has there been unprecedented warming?

A

1980

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10
Q

What was the warmest year on record with respect to the the 20C averages?

A

2015

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11
Q

What 2 things do SL measurements have to corrected for?

A
  1. Isostatic Uplift

2. Tectonic Uplift

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12
Q

What are the 2 main contributors to SLR?

A
  1. Thermal Expansion

2. Glacier/Ice Sheet Melt

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13
Q

What is happening to sea ice?

A

General Trend of Reduction in the Northern Hemisphere

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14
Q

Have modern instruments indicted that there is a global trends of anomalous conditions (the hockey stick)?

A

Yes

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15
Q

How much cooling have orbital variations caused in the North in the last 1000 years?

A

~0.2 Deg C

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16
Q

What can orbital timescales not be used to explain?

A

The unprecedented warming

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17
Q

What can decadal to century timescales be used to explain?

A

Variations on weekly, monthly and yearly timescales

18
Q

What are annular modes?

A

Changes in the N/S shift of the atmospheric masses between the polar regions and the mid latitudes

19
Q

What is NAM and its other 2 names?

A

Northern Annular Mode AKA Arctic Oscillation or North Atlantic Oscillation

20
Q

What is SAM and its other name?

A

Southern Annular Mode AKA the Antarctic Oscillation

21
Q

What is the NAO?

A

North Atlantic Oscillation – variations in atmospheric pressure between Iceland and the Azores (no distinct periodicity)

22
Q

What happens when the NAO is in +ve mode?

A

High pressure over the Azores, warmer conditions and wetter in the North

23
Q

What happens when the NAO is in -ve mode?

A

Decreased pressure difference, polar winds and wetter conditions in the Mediterranean

24
Q

What has happened to the NADW in the last 40 years and what is a possible explanation for this?

A

Rapid freshening – the NAO could be in +ve mode causing increased pptn in the Nordic Seas = more freshwater

25
Q

What can periods of solar minima/blocking cause? and when was this thought to be the case?

A
  • ve NAO (fresh and cold conditions)

e. g. Maunder Minimum during the Little Ice Age

26
Q

Long term, what does increased volcanism cause?

A

Increased CO2

27
Q

What impact does aerosols have on volcanism?

A

There are cooling events such as after Mount Pinatubo in 1991

28
Q

Following the eruption of Mount Pinatubo in 1991 what was the immediate and longer term cooling?

A

~0.6 Deg C in the immediate Summer and ~0.3 Deg C in the years after until noise meant that the effect was lost

29
Q

How often does El Niño occur?

A

Every 2-7 years

30
Q

During an El Niño year how much warming is there globally?

A

~0.1 Deg C

31
Q

Can El Niño explain the overall trend of warming?

A

No

32
Q

What happens in an La Niña year?

A

Low pressure in AUS and warm waters

Cold upwelling and High pressure in S.America

33
Q

What happens in an El Niño year?

A

Drought in AUS

Flooding and decreased upwelling with 1.5 Deg C warming in S.America

34
Q

What level is CO2 at today and what are the 2 main reasons for this?

A

> 400ppm

  1. Land Clearance
  2. Fossil Fuels
35
Q

How much more powerful is methane than CO2 but why is not having as much of an impact?

A

20x more but less concentrated/lower amounts of it

36
Q

What % of methane comes from natural and anthropogenic sources?

A

70% - anthropogenic

30% - natural

37
Q

What did the AOGCM modelling show?

A

That natural and anthropogenic forcing was needed to explain the global mean surface temperature anomalies in the hockey stick

38
Q

Which IPCC report outlines the anthropogenic forcings and had headline statements addressing observed changes and causes for climate change?

A

AR5 (2013)

39
Q

Cooling over the last millennium is caused by what?

A

Natural Causes

40
Q

Warming over the last 200-250 years is caused by what?

A

Anthropogenic Causes

Paleoclimate (10 decks)

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