Week 19 Flashcards
Termination I
Last deglaciation
Several meltwater induced climatic events
Antarctic cold reversal led YD
8.2ka event not global?
Rest of holocene fairly quiet
Holocene Climatic Optimum
= warm period 9000-5000 years BP
~5’C warmer at Poles > present
Different moisture distribution
Predictable from orbital forcing calculations
Climate over the last 2000 years
Includes (1) Medieval Warm Period and (2) Little Ice Age
Proxies/instrumental data
Prior = land-based records
Mild climate fluctuations
Proxy examples for the last 2000 years
Ice cores
Tree rings
Historical documents
Painting e.g. Peter Robinson ‘Weather’ 2005
- LIA = colder/cloudier in N Europe > Med
Medieval Warm Period
Vikings = colonies on Greenland
- exploration from Norway/Sweden/Denmark 800-1200AD
Inuits from Alaska hunting Bowhead Whales colonise E Canadian Arctic
England Wine
Farming higher altitudes/latitudes through Scandinavia
The Little Ice Age
Began 1300AD with increasing sea ice in N Atlantic (stopped travel)
- by 1400AD Greenland Viking Colonies lost
Glaciers grew
Lakes froze
Rivers/canals NW Europe froze
Europe crops less productive
Cause of the LIA
- SOLAR ACTIVITY
2. VOLCANIC ACTIVITY
- SOLAR ACTIVITY
Wolf/Sporer/Maunder/Dalton sunspot minima
More sunspots = more active/bright sun
Solar irradiance matches with sunspot index = solar activity proxy
CYCLES:
11 years = Schwab
22 years = Hale
88 years = Gleissberg
Sunspot =
area of v high magnetic activity
Sunspot components
Umbra = sunspot
Penumbra = around sunspot
Faculae = compensate = brighter
- VOLCANIC ACTIVITY; eruptions
1815 Tambora = largest in recorded (!) history = 150m3
1816 = year without summer
1812 = Soufriere, Saint Vincent
1814 = Mayon, Philippines
- VOLCANIC ACTIVITY; results
Taranto, S Italy = red/yellow snow
N England coldest July 20 years (-~5’C)
Lasted 1-3 x longer than sulphate aerosol residence time = +ve feedback?
- VOLCANIC ACTIVITY; mystery eruptions
1257 = Rinjani/Samalas
- GISP2 ice core T anomaly/S
+ another mystery
Climate since the LIA
If no industrial revolution = ice age?
BUT
- initial ~1880-1940 warming
- little change (cooling?) 1940-mid 1960s
(coal = pyrite = oxidised = sulphate aerosols) - parts of word more/less rain, overall more
- more CO2 in atmosphere now than any point in RECENT history
- CH4 + NOx higher than past
Mauna Loa
Longest instrumental CO2 record
Pollution doesn’t contaminate
Seasonality due to northern hemisphere
Climate since 1850; effects
Rate is alarming
Distribution of cities/population/agriculture
T/rain/drought
Coastal cities and SL rise
= adaptability is good
Climate since 1850; facts
Holocene T
- lat-dependent insolation = main control under 1850 when all lats increased
SL rise (tide gauges/satellites) = 30cm/century
- glacier melt
- thermal expansion
- spatial differences (due to ice age/plate tectonics theory)
Glaciers
Warm Arctic warm permafrost = reduce permafrost area = release CO2 = +ve feedback
WAIS>EAIS (newer = less stable)
OERLEMANS:
1) receding worldwide
- 83% of mountain glaciers receding
- -1m/yr average
2) T matches other proxies
3) Scandinavian anomaly; Engabreen glacier, Norway +0.64m/yr
- snowfall increased in some places due to warming
N.B. CHERRY PICKED????
Why has an Anthropocene been defined?
Due to species extinctions/climate changes
Classic Anthropocene theory
Natural processes controlled climate until Industrial Revolution
Then +CO2/hockey stick graph
N.B. Volcanic 20th century cooling
Solar activity increases from LIA
Friss-Christiansen and Lassen 1991
Sunspot cycle LENGTH most important = ctronols climate
Nearly perfect correlation; much better than CO2
Effects of climate change
More heat extremes
Drought
Increase in SL
- thermal expansion
Temporary severe cold spell?
Rapid migration of ecological zones
Long term forecast; general
Increase in solar irradiance
Slow warming next few billion years
Increase in humidity
Long term forecast, 1.1 billion years
Sun 10% bright than now
Some water escaped to space
= warm with abundant rainfall
Long term forecast; 3.5 billion years
Runaway greenhouse effect, boiling/evaporation of oceans
= very warm, cloudy, widely scattered showers
Long term forecast; 6 billion years
Sun –> red giant, mercury (+Earth) engulfed by sun
= hot
