Recent Climates

Question 1

Proxy: Ice Cores

Answer 1

snowflakes deposit different forms of water over time
trap atmospheric gasses as compressed over long periods of time

measures: global temperatures, global precipitations, climatic events

Question 2

Precipitation measurement from Ice Cores

Answer 2

ratio of O16/O18 (common/more rare) over time can be correlated with current global temps and precipitation patterns

those two isotopes
O16 lighter so more likely to evaporate
O18 heavier, so more likely to condense

when overall earth climate is really cold, very little O18 makes it to the permanent poles (it rains out on its way)
when climate is warm, much more O16 and O18 make it to the poles (more ice cores)

Question 3

Pollen Data

Answer 3

pollen doesn’t break down, builds up in soil and sediment

can be used to identify what plant species were in that region at that time and how it changed over time

temperature and precipitation

Question 4

Tree Rings

Answer 4

wider rings = more growth, optimal conditions
each ring one season of growth, since today

can get rings from dead trees, just have to figure out with other trees that around and line up some part of their tree rings

Question 5

Coral and Bivalves

Answer 5

Living ones old as 5000
seasonal growth cycles affected by climate
lining up growth ring overlap with dead ones to know even more

Question 6

Direct Measurement examples

Answer 6

ship logs
thermometers on land
written records
can combine with proxies to get accurate picture

Question 7

Pleistocene start and end

Answer 7

2.5my - 10,000
Start: formation of Isthmus of Panama deflected warm ocean currents to more northern latitudes, more rain –> more snow
positive feedback towards glaciation

End (unclear):
possible release of CO2 from southern oceans
Milanković cycles

Question 8

Last Glacial Maximum

Answer 8

~18000 years ago during pleistocene
allowed for travel between Asia and North America
major impact on human populations
humans evolve and later cold forced several genetic bottlenecks

Question 9

Younger Dryas

Answer 9

rapid climate change
temperatures dropped 4-10C in a few decades
cause: mass release of freshwater from melting NA glacier
warm water no longer moving to north latitudes
proxy: ice cores and pollen data

Question 10

Holocene

Answer 10

~11,650 years ago
very stable period
changing rain, disappearnance of great lakes latitudes, vegetation regimes, sea levels, coastlines

first agricultural revolution ~10,000 years ago because of predictable climate
domesticated plants

Question 11

Little Ice Age

Answer 11

fluctuating periods of cold temps between ~1300s and 1850
most severe in Europe
minor disruption in Holocene climate