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Causes of
climate change
 The Fourth IPCC Report, 2007, WMO,
Geneva
(http://www.ipcc.ch/publications_and_data
/publications_and_data_reports.htm)
 David Archer, 2007, Global warming,
understanding the forecast, Blackwell
Publishing
 Robert Henson, 2008, Climate change.
The symptoms, the science, the solutions,
Rough Guide, LTD.
Reasons of climate change
natural
changes of orbital
parameters
anthropogenic
changes in atmospheric
composition
changes of solar activity
changes in land use
volcanic activity
urbanization
orogeneza
deforestration
changes in continents
position
Orbital parameters of the Earth
eccentricity of Earth orbit
tilt of Earth axis
precession
The Earth orbit is an ellipse
and the center of mass of the
system is located in one of the
focus of this ellipse.
Orbital eccentricity shows
how big is the difference
between this ellipse and the
circle.
The eccentricity of an ellipse, usually denoted by ε or e, is the
ratio of the distance between the foci to the length of the major
axis. The eccentricity is necessarily between 0 and 1; it is zero if
and only if a =b, in which case the ellipse is a circle. As the
eccentricity tends to 1, the ellipse becomes more elongated, and
the ratio a /b tends to infinity
Orbital eccentricity
The eccentricity of the Earth's orbit is currently about 0.0167.
Over thousands of years, the eccentricity of the Earth's orbit
varies from nearly 0.0034 to almost 0.058 as a result of
gravitational attractions among the planets. At the moment the
distance between the Earth and the Sun changes from 146 × 106
km to 156 × 106 km, czyli o ok. 10 × 106 km. Together with changes
of the Earth-Sun distance there is a change in insolation (total
solar radiation coming to the Earth from the Sun). The main
cycle of orbital is about 100 000 years.
Precession refers to a change in the
orientation of the rotation axis of a
rotating body.
Axial precession is the movement of the rotational axis of an
astronomical body, whereby the axis slowly traces out a cone.
In the case of the Earth, this type of precession is also known
as the precession of the equinoxes or precession of the equator.
The Earth goes through one such complete precessional cycle
in a period of approximately 25,800 years, during which the
positions of stars as measured in the equatorial coordinate
system will slowly change; the change is actually due to the
change of the coordinates. Over this cycle the Earth's north
axial pole moves from where it is now, within 1° of Polaris, in a
circle around the ecliptic pole, with an angular radius of about
23.5 degrees. The shift is 1 degree in 72 years, where the angle
is taken from the observer, not from the center of the circle.
The effects of axial precession on the seasons, relative to perihelion and
aphelion. The precession of the equinoxes can cause periodic climate
change (Milankovitch cycles), because the hemisphere that experiences
summer at perihelion and winter at aphelion (as the southern
hemisphere does presently) is in principle prone to more severe seasons
than the opposite hemisphere.
In our solar system, the
Earth's orbital plane is
known as the ecliptic, and
so the Earth's axial tilt is
officially called the
obliquity of the
ecliptic.
The Earth currently has an axial tilt of about 23.44°. The axis remains
tilted in the same direction towards the stars throughout a year and
this means that when a hemisphere (a northern or southern half of the
earth) is pointing away from the Sun at one point in the orbit then
half an orbit later (half a year later) this hemisphere will be pointing
towards the Sun. This effect is the main cause of the seasons.
Whichever hemisphere is currently tilted toward the Sun experiences
more hours of sunlight each day, and the sunlight at midday also
strikes the ground at an angle nearer the vertical and thus delivers
more energy per unit surface area.
The obliquity of the ecliptic is not a fixed
quantity but changing over time in a
cycle with a period of 41,000 years.
Lower obliquity causes polar regions to
receive less seasonally contrasting solar
radiation, producing conditions more
favorable to glaciation. Like changes in
precession and eccentricity, changes in
tilt influence the relative strength of the
seasons, but the effects of the tilt cycle
are particularly pronounced in the high
latitudes where the great ice ages began.
Obliquity is a major factor in
glacial/interglacial fluctuations
SUNSPOTS
http://www.globalwarmingart.com/wiki/File:Sunspot_Numbers_png
Svensmark H., 2007, Astronomy & Geophysics, 48: 1-19.
Volcanic eruptions
Explosive volcanic eruptions
send enormous amounts of dust
to stratosphere
Why Study Volcanic Eruptions and Climate?
It helps us to improve climate models.
Radiative and dynamic aspects of models used for other problems can
be tested by these large, episodic events.
It allows us to make seasonal and interannual forecasts following large
volcanic eruptions.
Winter warming and summer cooling follow large tropical eruptions, like
El Chichón (1982) and Pinatubo (1991). Summer Indian monsoon failure will
follow large high latitude eruptions.
From Alan Robock
Why Study Volcanic Eruptions and Climate?
It provides an analog for some parts of the nuclear winter theory.
Rapid global aerosol transport and surface cooling from large aerosol
loading provide natural analogs that support the nuclear winter theory.
It allows us to separate the natural causes of interdecadal climate change
from anthropogenic effects.
The anthropogenic cause of recent global warming is strengthened after
accounting for volcanic effects.
The response to volcanic eruptions allows us to better understand the
impacts of anthropogenic climate change on life.
Biospheric responses and aspects of the carbon cycle have been
clarified.
More Reflected
Solar Flux
Stratospheric aerosols
(Lifetime  1-3 years)
Less
Upward
IR Flux
backscatter
absorption
(near IR)
H2S  H SO
2
4
SO2
CO2
H2O
Solar Heating
IR
Heating
Heterogeneous Less
O3 depletion Solar Heating
emission
IR Cooling
absorption (IR) emission
forward scatter
Ash
Reduced
Direct
Flux
Enhanced
Diffuse
Flux
Tropospheric aerosols
(Lifetime  1-3 weeks)
SO2  H2SO4
Indirect Effects
on Clouds
Effects
on cirrus
clouds
Less Total
Solar Flux
More
Downward
IR Flux
Volcanoes produced the
atmosphere and the oceans
Volcanic
emissions
N2
remains
N2
CO2
photosynthesis
O2
H2O
condensation
oceans
99% of
atmosphere
Mt. Erebus, Oct. 3, 2004
Volcanic eruptions
Dust causes warming of the
stratosphere and cooling of the
troposphere
Three months after the June 1991 eruption of Pinatubo volcano,
much of the 20 million tons of ejected sulfur dioxide had been
directed by zonal stratospheric winds and girdled the equator.
Mt. Pinatubo Eruption & Impact
Recorded changes in air temperature indicates the volcanic impact
on climate.
EFFECTS OF LARGE EXPLOSIVE TROPICAL
VOLCANOES ON WEATHER AND CLIMATE
EFFECT/MECHANISM
1. Enhance or reduce El Niño?
BEGINS
DURATION
1-2 weeks 1-2 months
Tropospheric absorption of shortwave and longwave radiation, dynamics
2. Reduction of diurnal cycle
Immediately 1-4 days
Blockage of shortwave and emission of longwave radiation
3. Summer cooling of NH tropics, subtropics Immediately 1-2 years
Blockage of shortwave radiation
4. Reduced tropical precipitation
Immediately
~1 year
Blockage of shortwave radiation, reduced evaporation
5. Reduced Sahel precipitation (?)
1-3 months 1-2 years
Blockage of shortwave radiation, reduced land temp., reduced evaporation
EFFECTS OF LARGE EXPLOSIVE TROPICAL
VOLCANOES ON WEATHER AND CLIMATE
EFFECT/MECHANISM
BEGINS
6. Ozone depletion, enhanced UV
DURATION
1 day
1-2 years
Dilution, heterogeneous chemistry on aerosols
7. Global cooling
Blockage of shortwave radiation
Immediately 1-3 years
multiple eruptions: 10-100 years
8. Stratospheric warming
Immediately 1-2 years
Stratospheric absorption of shortwave and longwave radiation
9. Winter warming of NH continents
½-1½ years 1 or 2 winters
Stratospheric absorption of shortwave and longwave radiation, dynamics
High latitude eruptions:
10. Cooling of continents
Immediately 1-2 years
Blockage of shortwave radiation
11. Reduction of Indian summer monsoon ½-1½ years 1 or 2 summers
Continental cooling, reduction of land-sea temperature contrast
Major volcanic eruptions
of the past 250 years
Volcano
Year
VEI
d.v.i/Emax
IVI
Lakagígar [Laki craters], Iceland
Unknown (El Chichón?)
Tambora, Sumbawa, Indonesia
Cosiguina, Nicaragua
Askja, Iceland
Krakatau, Indonesia
Okataina [Tarawera], North Island, NZ
Santa Maria, Guatemala
Ksudach, Kamchatka, Russia
Novarupta [Katmai], Alaska, US
Agung, Bali, Indonesia
Mt. St. Helens, Washington, US
El Chichón, Chiapas, Mexico
Mt. Pinatubo, Luzon, Philippines
1783
1809
1815
1835
1875
1883
1886
1902
1907
1912
1963
1980
1982
1991
4
2300
7
5
5
6
5
6
5
6
4
5
5
6
3000
4000
1000
1000
800
600
500
500
800
500
800
1000
0.19
0.20
0.50
0.11
0.01*
0.12
0.04
0.05
0.02
0.15
0.06
0.00
0.06
—
Major volcanic eruptions
of the past 250 years
Volcano
Year
VEI
d.v.i/Emax
IVI
Lakagígar [Laki craters], Iceland
Unknown (El Chichón?)
Tambora, Sumbawa, Indonesia
Cosiguina, Nicaragua
Askja, Iceland
Krakatau, Indonesia
Okataina [Tarawera], North Island, NZ
Santa Maria, Guatemala
Ksudach, Kamchatka, Russia
Novarupta [Katmai], Alaska, US
Agung, Bali, Indonesia
Mt. St. Helens, Washington, US
El Chichón, Chiapas, Mexico
Mt. Pinatubo, Luzon, Philippines
1783
1809
1815
1835
1875
1883
1886
1902
1907
1912
1963
1980
1982
1991
4
2300
7
5
5
6
5
6
5
6
4
5
5
6
3000
4000
1000
1000
800
600
500
500
800
500
800
1000
0.19
0.20
0.50
0.11
0.01*
0.12
0.04
0.05
0.02
0.15
0.06
0.00
0.06
—
Santorini, 1628 BC
Tambora, 1815
Etna, 44 BC
Lakagígar, 1783
Toba, 71,000 BP
Pinatubo, 1991
Famous Volcanic
Eruptions
Krakatau, 1883
Agung, 1963
El Chichón, 1982
St. Helens, 1980
DISTRIBUTION
OF SURFACE
OCEAN
CURRENTS
Surface ocean currents in the Earth history
Climate Change Triggers
Figure 19.7A
Figure 19.7B
Earth's climate is affected by feedback loops such as the water vaporgreenhouse feedback, where increases in air temperature increases water vapor,
which is a greenhouse gas that increases temperature.
Plate tectonics and drift concentrated continents at higher latitudes allowed for
more ice cover, which reflected more sunlight and created a positive feedback to
cause greater cooling.
Tropospheric Aerosols
Auto emissions and wild land fires are 2 sources that emit aerosols into the
troposphere that reduce incoming radiation and have a net cooling effect on
earth's surface.
Aerosols & Pollutants
Human and natural
activities displace
tiny soil, salt, and
ash particles as
suspended
aerosols, as well
as sulfur and
nitrogen oxides,
and hydrocarbons
as pollutants.
Early Phase
• Surface temperature might have been as
high as 85 to 110 oC (compared to 15oC
today)
• Planet cooled, water vapor condensed to
form clouds and rain, hence oceans
• A lot of CO2 in atmosphere dissolved in
rainwater
• Life formed about 2 billion years ago, and
photosynthesis produced oxygen (O2)
• Ozone (O3) shield formed
Evolution of Atmosphere: Early
(Primeval) Phase
• Earth's birth was about 4.6 billion years ago
• Lava, ashes, gases from volcanoes
("outgassing") form Earth's primeval
atmosphere, hugging planet due to
gravitational field of Earth
• Atmosphere consisted of mostly CO2 (carbon
dioxide), N2 (nitrogen) and H2O (water vapor)
Evolution of Atmosphere:
Modern Phase
• Main atmospheric components are N2 (78.08%
by volume) and O2 (20.95%) in layer below 80
km; other constituents are water vapor, trace
gases and aerosols
– water vapor concentration is highly variable,
ranging from 0 to 4%
– trace amounts of CO2, O3 and other gases
– aerosols in atmosphere are tiny liquid and
solid particles from forest fires, wind erosion
of soil, salt from ocean spray, volcanic
emission, and meteoric dust
Variable & Increasing Gases
Nitrogen and oxygen concentrations experience little
change, but carbon dioxide, methane, nitrous oxides, and
chlorofluorocarbons are greenhouse gases experiencing
discernable increases in concentration.
FAQ 2.1, Figure 1. Atmospheric
concentrations of important longlived greenhouse gases over the
last 2,000 years. Increases since
about 1750 are attributed to
human activities in the industrial
era. Concentration units are parts
per million (ppm) or parts per billion
(ppb), indicating the number of
molecules of the greenhouse gas
per million or billion air molecules,
respectively, in an atmospheric
sample. (Data combined and
simplifi ed from Chapters 6 and 2 of
this report.)
IPCC 4th Report WG1
GWP Global Warming Potential
IPCC, 4th Report, WG1
Figure 2.10. Schematic diagram showing the various radiative mechanisms
associated with cloud effects that have been identified as signifi cant in
relation to aerosols (modified from Haywood and Boucher, 2000). The small
black dots represent aerosol particles; the larger open circles cloud droplets.
Straight lines represent the incident and reflected solar radiation, and wavy
lines represent terrestrial radiation. The filled white circles indicate cloud
droplet number concentration (CDNC). The unperturbed cloud contains
larger cloud drops as only natural aerosols are available as cloud
condensation nuclei, while the perturbed cloud contains a greater number of
smaller cloud drops as both natural and anthropogenic aerosols are available
as cloud condensation nuclei (CCN). The vertical grey dashes represent
rainfall, and LWC refers to the liquid water content.
Greenhouse effect
Energy coming to the
Earth’s surface
S    R  S0
2
Energy coming to the unit
of the Earth’s surface
  R2  S 0 1353
2
2
S

W

338
W
m
m
2
4   R
4
Greenhouse effect
S a  (1  0.28)  S  243W m
2
Energy absorbed by the
unit of the Earth’s surface
Ez    T
Ez  Sa
4
z
Energy emitted by the unit
of the Earth’s surface
Energy balance
Effective temperature of the Earth
T z  255.9K  17.3 C
0
Greenhouse effect
 Td   Td   Tz
4
4
4
4 2 4  4 2 

Tz
Td
Td
T z  2  255.9 K  304.5K  31 C
4
0