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Introduction to climate and
climate change
Deniz Bozkurt
ITU Eurasia Institute of Earth Sciences
[email protected]
The International Training Course on
“Climate Analysis and Applications”
Alanya
10-19 October 2011
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What is climate?
what is not?
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Climate

Average weather conditions observed over a long
period of time for a given area. At least a period of
30 years should be taken into account
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Climate is not weather...

Weather: conditions of
the atmosphere over a
short period of time
Climate is what we expect, weather is what we get!
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Weather changes, what about climate?

Climate also changes. Climate change;

Long term ve slow-growing changes due to natural or
human-induced activities.

Can be global or regional.

Global warming and global cooling represent different
phases of climate change.
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What is
natural variability
of climate ?
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Climate system
Atmosphere
Hydrosphere
Biosphere
Lithosphere
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Cryosphere
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Climate system
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Climate system – Energy balance
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Atmospheric circulation
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Oceanic circulation
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Coldest winter in 1000 years!!!
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Temperature change for millions of years
http://www.globalwarmingart.com/wiki/Temperature_Gallery
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Spectrum
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What are responsible for
natural variability?
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• Changes in solar energy reaching the earth
• Volcanic eruptions (and large meteorite impacts)
• Nonlineer structures of climate system (climate
feedbacks)
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Climate system and natural variability
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How to understand
natural variability of
climate?
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Paleoclimatology
Instrumental Record
Earth Before Instruments (multiple billions of years)
• Study of past climates:
For better understanding of present climate changes
and climate variability
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Paleoclimatology – Proxy data
• Environmental records from natural sources such as tree
rings, ice cores, corals, and ocean and lake sediments.
Tree
rings
Lake sediments
Corals
Ice cores
Ocean
sediments
David M. Anderson
Paleoclimatology Branch, NOAA’s National Climate Data Center & World Data Center for Paleoclimatology
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Paleoclimatology – Dating methods
• Radiosotopic- Decay of certain elements
(14C)
• Ice Cores
• Deep-Sea Cores
• Pollen Dating
• Dendrochronology
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Dating methods-Radiocarbon dating
• All living things absorb carbon,
either through photosynthesis
or the food chain.
• Almost all carbon is 12C,
however a certain (small
proportion) is 14C.
• 14C is a radioactive with
a half life of 5700 years.
• Dating technique is based on
the 14C / 12C ratio.
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Dating methods-Ice cores
• Isotope analysis (similar to
carbon, but for oxygen)
– Temperature can be related to
concentrations of different
kinds of oxygen isotopes
• Air bubbles in ice
• Matter in ice (dust, particulates)
– helps to date the ice core
• Contain extensive time series,
some reaching back hundreds of
thousands of years.
• Physical characteristics of ice
– Conductivity – If high, ice
contains lots of volcanic matter
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Dating methods-Ice cores
• Evaporation: lighter 16O evaporates more easily from a
water body resulting atmospheric H2O vapor is poorer in
18O than oceanic water
• Condensation: heavier 18O are precipitated faster than
lighter 16O;
• So: coldest snow is lightest (less heavy 18O
isotopes, more lighter 16O isotopes)
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Dating methods-Ice cores
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Dating methods-Ice cores
Atmospheric composition from air bubbles
During the long transition from snow to ice, air bubbles get trapped, providing
one of the best methods for determining past atmospheric composition for preinstrument time periods.
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Dating methods-Ice cores
Temperature and CO2 Concentration Change
Barnola, et.al. (PAGES/IGBP)
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Dating methods-Tree rings
• Using tree rings to study present climate and reconstruct past
climate
• The age of a tree can be determined by counting the annual
growth rings.
Tree growth is sensitive to
climate
......But, also sensitive to many other
variables
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Dating methods-Tree rings
• In temperate climates, one distinct growing season per year,
so one
growth ring = one annual ring
• New wood cells form in the cambium, underneath the bark
• Earlywoodhas large, thin-walled cells and appears light
• Towards the end of the growing season, cells are smaller and
thick walled and appear darker: latewood
• Earlywood+ latewood = growth ring
• The mean width of the tree ring is a function of many
variables:
-tree species,
-tree age,
-soil nutrient availability
-other climatic factors
Bradley, Paleoclimatology, 1999
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Dating methods-Tree rings
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Dating methods-Tree rings
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Dating methods-Others
Marine Sediments-Deep
Sea Core Dating
• Sediments (dead organisms, runoff
from land) accumulate in ocean
basins
• Sediments can be analyzed to learn
about things like sea surface
temperature, ice extent, humidity
over land areas, wind direction at
surface, ocean salinity, and more!
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Dating methods-Others
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Dating methods-Others
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Dating methods-Others
Polen Dating
• Palynology: the study of pollen & spores
• Pollen deposits such in lakes, etc., supply a sequential record of
changes in vegetation since the last Ice Age
• Pollen analysis of lakes and bogs to study humans as agents of
vegetation change rather than causes such as climate
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Changes in solar energy: Milankovitch Cycles
Milutin Milankovitch
- 1879 – 1958
- Serbian geophysicist
- 1920: Milankovitch cycles
• In the last 3 million years, the ice
sheets over North America grew
and melted over short intervals.
• Summer insolation controls North
Hemisphere ice sheet growth. Ice
growth occurs during times when
summer insolation is low in high
northern latitude.
Rahmstorf and Schellnhuber (2006)
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Changes in solar energy: Milankovitch Cycles
Eccentricity: 100, 000 yr cycle
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Changes in solar energy: Milankovitch Cycles
Obliquity: 41, 000 yr cycle
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Changes in solar energy: Milankovitch Cycles
Precession: 23, 000 yr cycle
The major axis of each planet's elliptical orbit also precesses within
its orbital plane, in response to perturbations in the form of the
changing gravitational forces exerted by other planets. This is
called perihelion precession.
It is generally understood that the gravitational pulls of the sun and
the moon cause the precession of the equinoxes on Earth which
operate on cycles of 23,000 and 19,000 years.
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Changes in solar energy: Milankovitch Cycles
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Changes in solar energy: Milankovitch Cycles
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Glacial-Interglacial periods
Glacial
Ice Growth Configuration: Low eccentricity
Low Tilt
Large Earth-Sun Distance in Summer
Net Effect:
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Less seasonal contrast
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Glacial-Interglacial periods
Inter-Glacial
Ice Growth Configuration: High eccentricity
High Tilt
Small Earth-Sun Distance in Summer
Net Effect:
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More seasonal contrast
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Glacial-Interglacial periods
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Abrupt climate changes
Younger Dryas
•Younger Dryas- cooling event ~11.7 ky
–Named for Arctic flower that readvanced in
Europe
•Dryas octopetala
–Return of conditions similar
to LGM- not quite as extreme
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Abrupt climate changes
Younger Dryas
•
•
•
•
•
•
•
•
~7°C cooler in North Atlantic
Advance of Polar Front (to almost 45°)
Changes in vegetation
Drier/Dustier
Small advance in ice sheets (not a clear ice
volume event)
Climate signal in Greenland Ice Sheets
Changes in deep circulation
Centered in North Atlantic, but much more
widespread
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Abrupt climate changes
Younger Dryas
• Centered in North Atlantic, but much more widespread
– Tree ring studies- western US
– Tropical Indian Ocean- cooling
– Florida Lakes
– Pacific circulation
– Drying in North Africa
– Advance of mtn glaciers- New Zealand
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Abrupt climate changes
Heinrich Events
• Believed to represent cooling
events
• Ice sheets expanded far enough to
calve
• Surges of Laurentide ice sheet
(detrital carbonate, isotopic
studies of provenance)
Ruddiman, 2000
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Abrupt climate changes
Dansgaard / Oeschger Events
• Characterized by rapid
warming in the N.
Atlantic, followed by
slower cooling
• Quasi-Periodic, with a
timescale of ~1400 years
• Recorded by diverse
climate proxies
• Evidence for global
climatic effects
ftp://ftp.ngdc.noaa.gov/paleo/icecore/greenland/summit/grip/isotopes/gripd18o.txt
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Abrupt climate changes
Medieval Warm Period & Little Ice Age
The terms “Medieval Warm Period”
and “Little Ice Age” have been used
to describe two past climate epochs
in Europe and neighbouring regions
during roughly the 11th to 14th and
17th to 19th centuries, respectively.
The timing, however, of these cold
and warm periods has recently been
demonstrated to vary geographically
over the globe in a considerable way.
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Changes in sunspots
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Volcanic eruptions
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Volcanic eruptions: 1816 Year without summer
1815: Tambora Volcanic Eruption
Eruption column reached an altitude
about 43 km…
Volcanic
winter
1816 summer temperature anomaly with respect to 1971-2000 climatology. Data source:http://picasso.ngdc.noaa.gov/paleo/data/eurotemp
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Nonlineer climate system: ENSO
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Nonlineer climate system: ENSO
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Southern Oscillation and NINO3.4 Indice
http://graphics8.nytimes.com/images/misc/pixel.gif
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Nonlineer climate system: NAO
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Nonlineer climate system: Feedbacks
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Nonlineer climate system: Feedbacks
• Water vapour (positive feedback)
Increases evaporation
Increased
temperature
Increased
water vapor
Warms atmosphere
• Albedo (positive feedback)
Increased
temperature
Decreased
albedo
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Decreased
snow cover
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Nonlineer climate system: Feedbacks
• Clouds (positive and negative feedbacks)
• Cirrus clouds warm the atmosphere
• Stratocumulus clouds cool the
atmosphere
• But there are many uncertainties!!!
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...
Briefly...
PDO
ENSO
SOLAR
FORCING
NCP
Volcanic
Eruptions
Feedbacks
...
NAO
+
CLIMATE
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Human impact on climate?
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Temperature change in last 2000 years
(Proxies...)
Temperature change in last 2000 years over the Northern Hemisphere
(Instrumental record is shown with black line).
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Has temperature increased due to changes in CO2?
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Are fossil fuels really bad?
“Fossil fuels have lifted people in the industrialized
countries out of misery, allowing the average person
to live like a preindustrial king” (Fixing Climate)
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American Dream!
about.com
Why inconvenient truth?
Because, people love comfort!
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We are also on the same way!!!
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The atmosphere
Meteorological events
occur in the first 11 km of
the atmosphere, called
“troposphere”
Nitrogen:
Oxygen:
Argon:
Carbondioxide:
%0.03
%78
%21
%0.9
The amount of CO2 is too low compared to other gases!
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So, why we blame CO2?
Greenhouse effect:
Greenhouse gases absorb and re-emit the longwave radiation emitted from surface. This leads to warming of the earth’s
surface and near-surface layers of the atmosphere.
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Greenhouse effect of the atmosphere
No atmosphere
•Scorching days
•Freezing days
•Average surface
temperature: -18 oC
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Pre-industrial
•H2O, CO2, O3 gases
•CO2 concentration:
285 ppm
•Average surface
temperature: 16 oC
Present
•More greenhouse gases
•CO2 concentration:
384 ppm
•Average surface
temperature: 16+0.74 oC
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Who is responsible for how much?
No data
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0
94 tons/person
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Are we only perturbing
the atmosphere?
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No! We’re changing the land surface…
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Climate system response to
all these changes?
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GCC (http://climate.nasa.gov)
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Global surface temperature has been increasing
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Arctic sea ice has been melting
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Land ice has been melting
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Sea level has been rising
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Conclusion: Symptoms indicate
that we’re on fire. Faster and
worse events can take place due
to unpredictable changes related
with the nonlineer structure of
climate system!!!
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