Climate and Climate Change
Records
Definitions
• Weather:
– State of the atmosphere at a particular point in time.
– Look outside.
• Climate:
– The accumulation of “weather” (atmospheric state)
over a longer time period.
– Look outside for a really long time and do statistics.
– A combination of temperature and precipitation.
“Climate is what you expect … Weather is what you get.”
Climate VS Weather
• Longer-Term (Years
and longer)
• Broad composite of
average condition of a
region (e.g., temp,
rainfall, etc)snowfall,
ice cover, winds)
• Mean state of a
specific region
• An envelope of values
• Shorter-term (minutes
to days).
• State of atmosphere
(temp, press, winds,
sky cover, rainfall,
etc).
• Specific location for
specific time.
• A single number
HOW DO WE CLASSIFY CURRENT
CLIMATE?
Climate Classification:
• A consistent climate
classification scheme to
understand numerous
climate regions.
• Earliest known scheme
was used by the ancient
Greeks about 2200 years
ago.
• Morphed into the broad
scheme to the right.
• 3 Major regions: Frigid,
Temperate, Torrid.
Köppen climate classification system
• Based on a database of annual and monthly average
temperature and precipitation
• Four of five major groups classified by temperature
• Fifth group classified by precipitation
• Subdivided the five groups further based on
temperature and precipitation relationships
• Köppen letter code system
– Three letters; first describes group, second describes
precipitation, third describes temperature
• Used as a springboard for modified Köppen System
Modified Köppen Classification System
• Designated by a descriptive name and a
series of letters
• First letter = major climate group
• Second letter = precipitation patterns
• Third letter (if there) = temperature
patterns
HOW DO WE DETERMINE PAST
CLIMATE?
Proxy Records
Sources
• Tree Rings
• Ice cores
• Documentary data
• Thermometers
Historical Record
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Instrumental record ( ~150 years)
Written accounts
Art
Pictures
Grinnell Glacier at Glacier National Park
1910
1997
Rate of Glacial melt in last 20 years = 4x historical rate
Portage Glacier: Alaska
Snow Cover Reduced
• Number of days per
year with snow cover
has reduced since
early 1970’s
• Water storage in snow
pack is reduced
• More precipitation is
rain
15
Frozen River Thames
Paleoclimatology
• Definition: The study of past climates.
• Why? To help understand current climates
and future climates.
• What about thermometers? They only go
back a few hundred years.
• So we use proxies, or substitutes, to
reconstruct past conditions.
Dendrochronology
• Tree rings!
• Most trees increase trunk diameter by adding one
concentric tree ring for each year of growth.
• Count the rings to determine how old the tree is.
• During more favorable years (mild temps. and/or
more precip.) tree rings are usually wider.
• Compare/correlating dead trees to living trees
helps determine catastrophic events.
• Period of record: 10-100s of years. In rare cases
1000s of years.
Cross dating
LONG-TERM CHANGES IN DROUGHT AREA IN THE 'WEST'
% DROUGHT AREA
100
THE CENTRAL DATES OF THE
SIGNIFICANT (p<0.05) EPOCHS
ARE INDICATED WITH ARROWS
1150 1253
936 1034
80
60
40
DRIER
20
0
WETTER
800
1321
1613
1829
1915
900 1000 1100 12001300 1400 1500 16001700 1800 1900 2000
YEAR
Southwestern US
Water is most precious, least
abundant resource…
Number of habitation sites
Drought and the Anasazi
Populations
expanded
dramatically during
wet years.
Sustainability of
population = water
Population collapses
related to
megadroughts
Pros and Cons
Dendrochronology
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Pros
Well understood.
Direct correlation
between growth and
moisture.
Indirect correlations
between growth and cloud
cover, temperature.
Location of tree is usually
known.
Local climate
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Cons
Only record the growing
season.
Tropical trees may not
have obvious annual
growth rings
No clear indication of
when tree died, therefor
harder to determine when
it lived.
Other influences of
growth other than
climate.
Local Climate
Ocean/lake sediments
• Lake and ocean sediment cores.
• Sedimentation rate.
– Varves: couplets of light (more energy) and dark bands
(less energy) produced in some lakes. Thicker = more
erosion.
• Trapped organic matter (radio carbon dating)
– Seeds, leaves, charcoal.
• Little critters (Foraminifera or forams and diatoms)
that die and sink to the bottom of the ocean and
we measure their 18O to 16O ratio.
• Period of Record: 10s – 10,000s of years
Oxygen Isotopes
– Oxygen Isotopes (atoms of the same element with
different atomic weights because they have
different numbers of neutrons) Oxygen 16 and
Oxygen 18.
– Both 16O and 18O are found in common molecules
such as water (H2O) and calcium carbonate
(CaCO3).
– The ratio of 18O to 16O in the water changes based
on the climate.
– 16O is lighter so it evaporates more easily, leaving
the heavier 18O in the ocean.
Oxygen Isotope Cycle
More 18O In ice
because more
heat energy
More 16O In ice
because less
heat energy
Ocean Cores
Lake cores
Varves
Pros and Cons
Ocean/Lake Sediments
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Pros
Relatively undisturbed
by humans
Fairly consistent rates,
especially in the
ocean
Long record.
Local climate
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Cons
Influences other than
climate (biology and
weather.)
Bioturbation (worms
borrowing!)
Can be expensive
Local climate
Ice Cores
• Drilling ice cores in glaciers and ice sheets all over the world.
• Dating from worldwide events like atom bombs.
• The more 18O in the ice the warmer it was because more heat
energy was available to evaporate the heavier oxygen isotope.
• Wind blown dust can hint towards global air circulation patterns
• Trapped air bubbles enable scientists to measure concentrations
of CO2 and other gasses that were present in the environment.
– Historically, the more greenhouse gasses there were the
atmosphere the less ice on earth.
• Period of record: 10s to almost 1,000,000 years
Ice Cores
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Age of ice (layers)
Isotope ratio (for temps)
Air bubbles (atm gas content)
Dust content (wind)
Salt content (wind)
Sulphuric acid content (volcanism)
Ice Cores
0˚C : Tipping Point for Climate
• Surface energy balance
– Feedback processes rest on crossing the 0˚C
threshold
– Above 0˚C , melt ensues, albedo change  positive
feedback
• Water storage
– Below 0˚C , H2O can be stored, not utilized by
plants, evaporate away etc.
– Above 0˚C , H2O runs off, leads to plant growth,
evaporation, etc.
Pros and Cons
Ice Cores
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Pros
Actual bubble of past
atmosphere
More global than other
proxy records.
Chemistry is pretty well
understood
Temperature proxy and
atmosphere bubble in
same location.
Easy to compare across
different locations.
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Cons
Can be hard to date.
Expensive and difficult
to obtain and store.
Glaciers are melting all
over the world.
Hard to find ideal
locations
Cold and hard to get to
locations.
Other
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Coral reefs
Relic soils
Pollen
Cave deposits
Shell fish
Sources
• Dr. Crystal Kolden
• Dr. John Abatzoglou
(http://webpages.uidaho.edu/jabatzoglou/)
More information:
• www.westernclimateinitiative.org/
• Icenetmatrix.com
• http://www.atmos.washington.edu/mm5rt/
• http://www.wrcc.dri.edu/research/jtwrcc/idaho-mon/
• http://www.wrcc.dri.edu/monitor/WWDT/
• http://www.cefa.dri.edu/Westmap/
• http://www.cpc.ncep.noaa.gov/products/predictions/90day/