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Palaeoclimatology > Projecting Future Climate Change > Flashcards

Projecting Future Climate Change Flashcards

1
Q

Fast Feedbacks

A
  • immediate to 10’s of years response e.g water vapour
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2
Q

Slow feed backs

A

1,000’s to 10,000’s of years response

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3
Q

Orbital forcing

A

0.25W/m^2

This is not enough energy to raise global temperature by 5 degrees Celsius. This indicates there are fast and strong Feedbacks amplifying the small forcing

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4
Q

Carbon cycle

A

Positive and negative feedback

Acts as a fertiliser for vegetation

30% of the CO2 from humans have been taken up by the ocean and vegetation. It is also amplifying the global temperature increase

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5
Q

Target CO2 emissions

A

2 degrees Celsius is too high based on most recent research. There USA strong likelihood that the sea level response will be exponential and 29cm is not realistic

Models used to predict the 2 degree Celsius did not consider ice sheet decay = linear trajectory - exponential increase

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6
Q

Dust group

A

Absorbs and scatters incoming shortwave radiation. Fertilises the oceans. Glacial periods contain higher dust content. Derived from South America exposed continental shelves and due to increased aridity. Most of the dust reaching Antarctica is from South America

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7
Q

Temperature group

A

Hydrogen stable isotopes record temperature. Comparison from benthic O^18 from forums. Confirms temperature signal after 800Kyr

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8
Q

CO2 group

A

Glacials= oceans are colder holding more CO2. Less upwelling due to increased sea ice and dust fertilisation causes increase phytoplankton and CO2 drawdown

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9
Q

Pulling records together

A

Temperature and CO2 is the same

Dust leads up to 5,000 years in all of the records. Decrease I. Dust = change in winds or increase in sea level to reduce arid conditions.

One hypothesis for the rise in CO2 at the end of the last glacial maximum (termination) is that reduced iron (dust) supply to the southern ocean caused by the increase of 80-100ppm CO2

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10
Q

Qua ternary Glacial - interglacial cycles

A

The last 2.7Ma characterised by glacial - interglacial cycle

The period contains the highest variability throughout the cenozoic force by the milankovitch cycles

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11
Q

Glacial periods characteristics

A
  • ice ages paced by changes in the earths orbit
  • large parts of Eurasia and North America ice covered
  • sea level = 130m lower
  • global temperature ~6 degrees lower. They were cooler because greater ice albedo and greater land albedo (less vegetation)
  • lower atmospheric GHGs
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12
Q

Conditions favourable for ice sheets

A
  • accumulation rates exceed ablation

- temperature

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13
Q

Temperature and ice mass balance

A

Limited by cold air not being able to hold water. High latitudes = winter temperatures always cold.

Winter is NOT the critical season. It’s summer melting which controls ice sheet growth. No matter how much snow falls during winter, it can easily melt if the following summer is warm and ablation is rapid

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14
Q

Terminating ice ages

A

Ice sheets melt when summer Insolation is high =’axial tilt is high

The change in solar radiation due to milankovitch forcing is

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15
Q

One possibility is gas trapping in the ice

A

Gases trapped during ice sintering (sealing). Gases younger than host ice due to air diffusion up to 50m.

Accumulation rate determines the gas age. Range from 100 - 2,000 years

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16
Q

Future global and regional climate change

A

Climate projects are made using climate models with various ranges of sophistication. All climate models look at earth system changes for the year 2100 AD, include higher than current atmospheric CO2.

All models project similar changes over the next few decades, the magnitude of change for the mid 21st century depends on the emissions scenario trying to project until the end of the century with all showing increase in CO2

17
Q

RCP2.6 CO2 emissions scenario

A

Mitigation scenario for energy and industry related CO2 emissions. Requires a 70% reduction in emissions. Without mitigation scenarios result in 2.6W:m^2 forcing

18
Q

Global average surface temperature

A

Surface warming likely to exceed 2 degrees and warning will continue to increase after 2100 for all scenarios except RCP2.6. RCP2.8 = over 11 degrees if not action is taken. Warming will not be regionally uniform.

19
Q

How do climate models work

A

A climate model is a mathematical representation of how ocean, land and atmosphere interact. The Earth’s component are divided into a set of boxes then layers. Most recent models include hydrological and carbon cycle.

Super computers sun models that incorporate many factors and great spatial detail. Evolution enabled by an increase in computational capacity. Super computer speeds have increased by a factor of a. Ill on since 1970s

20
Q

Super computer mid 1980s

A
  • low resolution

- prescribed ice

21
Q

Super computer early 1990s

A
  • first assessment report of the IPCC

- atmospheric models were coupled to a “swap” or “slab” ocean

22
Q

Super computer 1996

A
  • 2nd assessment of the IPCC

- additional aerosols = sulphate, volcanic activity

23
Q

Super computer 2001

A
  • 3rd assessment report of the IPCC

- Rivers, carbon cycle

24
Q

Super computer 2007

A
  • 4th assessment of the IPCC
  • interaction of vegetation
  • feedback albedo
  • atmospheric chemistry
25
Q

Geographic resolution

A

Northern Europe as an example of increasing resolution. Century simulations typically run with lower resolution models. Vertical layers are now over 30 ocean and atmospheric layers

DOE PCM = global climate model that is able to reconstruct the historical temperature record. Showing various forcing factors

26
Q

How feasible is an RCP3.6 emission scenario

A

Still technically feasible

Based on what society can do to create cleaner emissions. Needs full participation of all countries. Needs a 70% cumulative reduction in ghg from 2010 - 2100. Requires substantial change in energy use and CO2 reductions.

First step = baseline conditions
2nd step = effects of emission reduction

Th mitigation scenario implemented in image

27
Q

Climate change in the future

A

Climate change is a persistent threat. Paris agreement = 195 countries agree to keeping temperature increase belo 2 degrees 8o0 countries committed to use solar and wind power to reduce GHGs. For the first time, not only governments engaging in talks but businesses and environmental groups

28
Q

Carbon positive feed back loop

A 
Initial change
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Climate warming
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CO2 degas from oceans
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Increase atmospheric CO2
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CO2 acts as the
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Amplified warming
29
Q

Carbon negative feedback loop

A 
Initial change
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Climate warming 
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Tectonic uplift of mountains
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Exposed silicate rocks
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Chemical weathering drawdown atmospheric CO2
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Reduced warming

Palaeoclimatology (9 decks)

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