climate change Flashcards
marine sediments
shells and sediments have isotopic signatures of the h2o in which they were found.
o16 is lighter than 018 - snow contains 016 and sits on top of the water and makes the ocean higher in 018. ocean sediments high in 018 indicates that they were formed during a colder period. finding the ratio between 016:018 indicates climate at the time.
eval - limited to ocean climates - oldest way.
ice cores
longest ice core is 3km -8 glacial periods
300,000 years back
snow and ice fill cores during the colder periods which have a higher concentration of 016.
ice cores preserve ash + bubbles of atmospheric gas.
fossils
coral fossils - need specific environment to survive - 1*C and water depth.
eval - very specific to local area - doesnt demonstrate wide scale climate change.
dendrochronology
oldest tree - 5000 years old
trees form a cambium layer anually that depends on the temprature and the moisture of the conditions of that time.
eval - only specific to local reigon - needs to be used alongside other analytical technologies becuase not all trees develop a cambium layer or cambium layers are irregular.
lake sediments
pollen has tiny spores - produced in millions - which are scattered and preserved in mud + sediments . these can be found in fossils along with bettles and enables identification of the differnt plant and beetle species in the area and the climate that allows survival
eval - specific to small scale areas
continental drift
sig. changes to global climate and long term changes to glaciation
230 million years go panama formed 1 single land mass
eccentricity
milankovich cycles
- orbit
- every 100,000 years
- ice ages correspond to when the orbit causes the earth to be the furthest from thr sun (apehelion) rather than closest (perihelion).
obliquity
milankovich cycles
- tilt
- every 41,000 years (between 22-24.5*c)
- effects the intensity of the seasons e.g. smaller tilt means warmer in winter + cooler in summer
- ice doesnt melt which means a positive feedback loop begins and causes ice sheet expansion and triggers a galcial period becuase of the albedo effects
precession
milankovich cycles
- wobble
- every 22,000 years
- precession of the equinox
- influences intensity of the seasons and feeback loops which can trigger a glacial period.
what do the milankovich cycles represent?
- spacial and temporal
- all describe long-term, wide scale changes like glacials and inter-glacials
solar output - sun spots
the maunder minimum (when number of sun spots reduce to 0)
occured during the little ice age - end of 20th century
caused the river thames to freeze over
eval - short-term variations and effects the amount of energy (heat) transferred into the earths atmosphere
natural greenhouse gasses
plays an important role in enuring solar radiation doesnt immediately escape the atmosphere
changes in atmospheric gasses triggers global climate temp change
greenhouse effect triggers positive feedback loop
can cause glacials and interglacials
greenhouse gasses - water vapour, co2, 02, methane
volcanic activity
eruptions cause volcanic ash and sulfur dioxide pollute the air
as a reuslt incoming solar radiattion is reflected which decreases temp in the troposphere.
example - mount pinatubo - phillipines 1991 - releasing 20 million tonnes of sulfur dioxide - cause a 1.3*c drop in temp over a 3 year period.
eval - localised changes - short term
long term
how has the climate changed?
geologically over millions of years
medium term
how has the climate changed?
historical
last 1000nd years
