Holocene to the future Flashcards
1
Q
Termination I
A
- Name given to last deglaciation
- Consists of several melt water induced climatic events
- The Antarctic cold reversal led the YD
- 8.2 ka event not global?
- The rest of the Holocene fairly quiet
2
Q
Holocene Climatic Optimum
A
(aka: Hypsithermal, Altithermal, Holocene Thermal Maximum, and Megathermal)
- Warm period 9,000 to 5,000 years BP
- About 5 ºC warmer at poles than today
- Different distribution of moisture
- Predictable from orbital forcing calculations
3
Q
The Last 2000 Years
A
- Multiple proxy records mixed with instrumental data
- Proxies:
- Ice Cores
- Tree Rings
- Historical Documents
- Records almost entirely land-based prior to the instrumental record
- Mild climate fluctuations
4
Q
The Medieval Warm Period
A
- Vikings establish colonies on Greenland
- Inuit from Alaska hunting bowhead whales colonize eastern Canadian Arctic
- Wine produced in England
- Farming at higher altitudes and farther north throughout Scandinavia
- European/N. Hemisphere warmth; did the rest of the world warm? Probably no.
5
Q
The Little Ice Age
A
- Beginning in 1300 AD, sea ice in the North Atlantic increased, and travel to Greenland Colonies became difficult.
- By 1400 AD Greenland Viking Colonies lost
- Glaciers grew
- Sea ice became more extensive
- Lakes froze earlier
- Rivers/canals froze in NW Europe
- Crops in Europe were less productive
- Proxies:
- Paintings
- Diaries + letters
- During LIA the weather was cloudier and colder in Northern Europe than the Mediterranean
6
Q
What caused the Little Ice Age? (Sunspots)
A
1) Solar Activity
• Wolf, Sporer, Maunder, Dalton Sunspot Minima
• Maunder minimum (1650-1700) has almost no sunspots
o Late 1600s, was noted that sunspots vanished meaning there was less solar output
o Faculae = brighter parts of sun which are the hottest
• Leading theory for a while
7
Q
Measured solar irradiance matches up well with sunspot index
A
Different Cycles:
o 11-year: Schwab Cycle
o 22-year: Hale Cycle
o 88-year: Gleissberg Cycle
8
Q
What caused the Little Ice Age? (Volcanic Activity)
A
- Tambora erupts in 1815
- Largest eruption in recorded history
- 150 cubic meters of volcanic material ejected
- The year 1816 known as the “year without a summer”
- Widespread famine – Frankenstein written
- Krakatau (1883) blocked 20% of direct sunlight
- Tambora larger than this – 10-20x
- Not only major eruption during LIA: Soufriere, Saint Vincent (1812); Mayon, Phillipines (1814)
- Taranto, southern Italy: red and yellow coloured snow
- North England experienced coldest July in 200 years of record keeping: almost 5 C colder than usual
- For volcano to be effective it must reach stratosphere
- Releases sulphate aerosols
- Must pass the Tropopause – leaving the troposphere
- Otherwise will be rained out
- Once in the stratosphere it shall linger
9
Q
Mystery Eruptions
A
- Show up in GISP2 ice core data
- Sulphur peak
- No known calderas – Rinjani/Samalas 1257 now IDed
- No historical data – 1815 volcano significant
10
Q
Climate since the Little Ice Age
A
- Industrial Revolution: 1850 extensive amount of stored carbon burned - CO2 released to atmosphere
- Industrialisation could have potentially brought climate out of Little Ice Age and stopped a glaciation
11
Q
The LIA resulted from volcanism?
A
- Lasted longer than the 1-3-year residence time of sulphate aerosols in atmosphere
- Samalas most likely
- Cool the climate for 3 years = increased albedo, slow ocean circulation = climate changed long term
- Positive feedbacks extend effect?
12
Q
Global Warming since 1850
A
- General warming for the past century
- Not steady… initial warming from ~1880 to 1940
- Very little change (maybe even cooling) 1940 to mid- 1960s.
- Steady, rapid warming since the early 1970s.
- Environmentalism kicks off; less coal, more oil
- Burning coal leads to sulphate emissions which causes cooling (temporary)
- More oil = more warming
- Is the warming uniform across the planet?
- More ocean heating
- Rainfall increasing, stronger storms, more floods
- Parts of world are getting more rainfall, parts are getting less
- Overall increase in rainfall
13
Q
Mauna Loa CO2 record
A
- Longest instrumental CO2 record
- Not contaminated by ‘pollution’
- Seasonality controlled by northern hemisphere
- On a year-to-year basis, more CO2 released than is sequestered
- Shows cycle where summer vegetation takes in more CO2
- Every winter CO2 increased
- More sources than sinks – reducing vegetation, increasing emissions
- There is more CO2 in atmosphere now than at any point in recent geological history
- Not broken the 280-ppm ceiling in 800,000 years, until now
- Nitrous oxide levels higher than at any time in recent past
- Methane levels higher than at any time in recent past
14
Q
Global Warming since 1850
A
- Net change so far trivial by geological standards
- Rate not trivial
- Effect on ecosystems = mass extinctions
- All of the world’s cities, population, and agriculture are distributed based on current climate
- Rapid global climate change will alter temperature, rainfall, and drought distribution affecting agriculture and water resources
- The most successful cultures in climatically sensitive environments have been based on adaptability
- Our cities tend to be coastal – sea level is rising
- 1850 – all latitudes started warming for first time
- Arctic warming has resulted in permafrost warming, and reduction in the area of permafrost.
- Positive feedbacks as warming releases trapped CO2 and gas hydrates.
15
Q
Sea Level Rise
A
How do we know? • Tide gauges: 30 cm/century • Satellites: Also 30 cm/century Why is sea level rising? • Glaciers melting • Thermal expansion of the ocean • Not equal around the world • Spatial differences mostly related to last ice age and plate tectonics
16
Q
Antarctic Ice Sheet
A
- West Antarctic Ice Sheet warming more than East Antarctic Ice Sheet
- Is newer, less stable
- Passed threshold?
- Increased warmth leading to increased snowfall in places
17
Q
Glaciers worldwide in retreat
A
- Oerlemans studied historical glacier lengths and glacial dynamics
- Glaciers worldwide have been receding
- Temperature matches other proxies
- 83% of mountain glaciers receding
- On average ~ 1 meter of ice lost every 3 years
- Scandinavian glaciers tend to be growing - Engabreen glacier (Norway) with a thickening of 0.64 m/yr
- Beware of ‘cherry picked’ examples
- Norwegian glaciers (maritime) restricted by moisture amounts; as climate warms there is more moisture and therefore are growing – increasing snowfall
- WAIS collapse currently underway?
- Complete collapse in ~200 years?
18
Q
The ‘Anthropocene’
A
- Geological time periods defined by species extinctions and major changes in climate
- Increasingly it is viewed that we are longer in Holocene epoch
- Term coined in 2000 by the Nobel Prize winning scientist Paul Crutzen
19
Q
The Anthropocene: version 1 - The ‘classic’ version
A
- Climate controlled by ‘natural’ processes until Industrial Revolution
- Since 1850 large amounts of CO2 have been injected into atmosphere due to fossil fuel burning
- Instrumental records support available CO2 proxy records
- Mann et al. ‘Hockey Stick’ graph
- Radiocarbon confirms massive influx of ‘dead’ carbon since 1850
- Other forcing’s besides CO2 also active
- Volcanic activity produced 20th century cooling
- But solar activity is increasing from the LIA
20
Q
Effects of Global Warming
A
• More Heat Extremes
• Drought
• Rise in Sea Level (mostly due to thermal expansion)
• Temporary Severe Cold Spell?
o Melting ice sheets so rapidly = large influx of freshwater = Younger Dryas
• Rapid Migration of Ecological Zones
21
Q
The Anthropocene: Version 2 - The ‘Early Anthropocene’
A
- Initially proposed by Ruddiman
- The shift from hunter-gather to agricultural lifestyles led to increase in GHG
- Deforestation and rice cultivation in particular
- Dates of these events match deflection from natural trends
22
Q
The Long-Term Forecast
A
- Increase in solar irradiance through time
- Slow warming trend for the next few billion years
- Increasing humidity
- In 1.1 billion years: Sun will be 10% brighter than now. Some water lost to space. “warm with abundant rainfall”.
- In 3.5 billion years: Runaway greenhouse effect. Boiling and evaporation of the oceans. “Very warm, cloudy, with widely scattered showers”
- In ~6 billion years the Sun should turn into a Red Giant. Mercury (and Earth?) is engulfed by Sun. “Hot”
