10/7/10
The
Greenhouse
Effect
REVIEW
PROBLEMS
FROM
CHAPTER
6
‐
1,
3,
7,
8,
9,
12,
20,
21
Greenhouse
warming
and
global
warming:
“…the
average
global
air
temperatures
are
expected
to
increase
as
a
result
of
carbon
dioxide
and
other
greenhouse
gases
in
the
atmosphere.”
…”most
scien:sts
believe
that
such
global
warming
has
already
been
under
way
for
some
:me
and
is
largely
responsible
for
the
air
temperature
increase
that
has
occurred
since
1860.”
IPCC
EPA – climate change
EPA – Kid’s site
Surface temperature anomalies relative to 1951–1980 from surface air
measurements at meteorological stations and ship and satellite SST measurements
The
Earth’s
Energy
Source
λpeak
(in
microns)
=
2897/T
T
~
5800
K
Goddard Instituted for Space Studies web site
What
happens
to
sunlight
that
strikes
the
Earth’s
surface?
• 
50%
absorbed
by
soil,
vegetaHon,
buildings
and
water
bodies
• 
20%
absorbed
by
water
droplets
and
gases
(O3,
O2,
CO2)
• 
remaining
30%
reflected
by
clouds,
parHcles,
snow,
ice,
etc.
1
10/7/10
Long
–term
historical
trends
in
surface
temperatures
A
B
C
‘A’
–
slight
increase
in
sunlight
intensity;
lack
of
volcanic
acHvity
‘B’
–
increased
volcanic
acHvity
‘C’
‐
anthropogenic
Earth’s
Energy
Emissions
and
the
Greenhouse
Effect
Random
direcHon
of
emission
of
IR
radiaHon
“The
phenomenon
of
intercep:on
of
outgoing
IR
radia:on
by
atmospheric
cons:tuents
and
its
dissipa:on
as
heat
to
increase
the
temperature
of
the
atmosphere
is
called
the
greenhouse
effect”
Note:
Without
the
greenhouse
effect,
the
earth’s
temperature
would
be
‐18˚C
rather
than
+
15˚C!
Earth’s
surface
is
warmed
AS
MUCH
by
indirect
process
as
by
solar
energy!
Why
doesn’t
the
earth
emit
visible
or
UV
light?
(hint,
the
temperature
of
the
earth
is
about
300
K
and
λpeak
=
2897/T
)
Aha,
λpeak
=
9.65
microns;
(actual
peak
=
13
microns…)
Enhanced
Greenhouse
Effect
Most
predominant
greenhouse
gases
Desert
nights?
to
date:
• 
water
vapor
(~75%)
Cloudless
winter
nights?
• 
carbon
dioxide
(~
25%)
The
Major
Greenhouse
Gases
–
CO2
and
IR
AbsorpHon
Peak
around
13
microns
•  small
increases
in
trace
gases
that
absorb
IR
energy
results
in
conversion
of
an
even
greater
fracHon
of
the
outgoing
thermal
IR
energy
than
occurs
at
present
2
10/7/10
Major
Greenhouse
Gases
cont’d:
Effect
of
various
gases
on
the
amount
of
Thermal
IR
light
leaving
the
earth’s
surface
Changes
in
Carbon
Dioxide
ConcentraHon
Note
seasonal
fluctuaHons
*
Historical
data
from
air
trapped
in
ice‐core
samples
from
AntarcHca
Natural
and
anthropogenic
sources
of
CO2
CO2
+
H2O
sunlight
O2
+
polymeric
CH2O
Average
person
in
industrialized
countries
is
responsible
for
the
release
of
5
metric
tons
of
CO2
from
carbon‐containing
fuels
each
year!
Carbon
Dioxide:
Atmospheric
LifeHme
and
Fate
of
Its
Emissions
• 
Only
permanent
sink
is
deep
ocean
• 
50‐200
years
to
reach
new
equilibrium
• 
motor
vehicles
• 
heaHng
and
cooking
• 
producHon
of
goods
• 
transportaHon
of
goods
• 
deforestaHon
and
subsequent
wood
burning
(~
25%
of
all
anthropogenic
CO2)
3
10/7/10
Water
Vapor
and
IR
AbsorpHon
Methane
as
a
Greenhouse
Gas
Atmospheric
window
• 
ConcentraHon
of
water
vapor
is
determined
primarily
by
temperature
and
other
weather‐related
phenomena
• Equilibrium
vapor
pressure
increases
exponenHally
with
temperature
• Atmospheric
content
of
water
vapor
has
increased
over
the
past
30
years
• PosiBve
feedback
–
increased
[CO2],
increased
[H2O],
increased
greenhouse
effect!
Methane
Emission
Sources
7.7
microns
Recall
that
CH4
CH2O
CO
CO2
Per
molecule,
CH4
is
23
x
more
efficient
than
CO2
at
raising
air
temp;
however,
CO2
concentraHon
has
increased
so
much
more
and
is
much
longer
lived
making
it
more
important
at
heaHng
the
atmosphere
Methane:
ConcentraHon
Trend
and
Possible
Future
Increases
Decreases
in
CH4
• draining
of
wetlands
• 
drying
of
wetlands
from
global
warming
• Mt.
Pinatubo?
??
Tropical
deforestaHon
• 
~
70%
anthropogenic
reduced
aerobic
methane
• 
rice
producHon
producHon??
• 
anaerobic
decomposiHon
in
landfills
• 
cavle,
sheep
• 
mining
of
coal;
crude
oil
(incomplete
flaring)
• 
pipeline
outgassing
• 
natural
sources
include
anaerobic
decomposiHon
(wetlands)
• Note:
deep
small
reservoirs
emit
much
less
methane
than
shallow
ones
containing
large
volumes
of
flooded
biomass
–
e.g.
for
hydroelectric
power!
Increases
in
CH4
• 
fossil
fuel
use
in
Asia
• 
increase
in
natural
gas
pipelines
• 
Increased
anaerobic
decay
with
increased
temperatures
• 
MelHng
of
permafrost
would
release
CH4
and
and
allow
decomposiHon
of
organic
maver
in
the
permafrost
• 
Clathrates
–
CH4.6H2O
and
runaway
greenhouse
effect
4
10/7/10
Nitrous
Oxide
–
N2O,
CFCs,
Sulfur
Hexafluoride
and
Tropospheric
Ozone,
Climate
Change
and
Aerosols
N2O
is
296
x
as
effecHve
as
CO2
in
causing
an
immediate
increase
in
global
warming;
absorbs
IR
light
at
8.6
µM;
<40%
of
emissions
are
anthropogenic
w/balance
coming
from
oceans,
and
processes
occurring
in
tropical
soils
CFCs
–
absorb
strongly
from
8
–
13
µM
;
long
residence
Hmes;
Montreal
Protocol
SF6
–
23,900
x
greater
than
CO2
in
global
warming
potenHal;
3200
year
lifeHme;
used
as
an
insulaHng
gas
by
electrical
uHliHes
and
in
the
semiconductor
industry
as
an
insulaHng
gas
O3
(tropospheric):
absorbs
IR
radiaHon
in
the
9
–
10
µM
region;
maybe
as
much
as
10%
of
global
warming
potenHal
is
due
to
anthropogenic
ozone
Aerosols
and
Climate
Change
conHnued
Some
parHcles
reflect
sunlight
and
lead
to
cooling
of
the
air
mass
and
the
surface
below
it
(e.g.
sulfate
aerosols)
Some
parHcles
absorb
certain
wavelengths
of
light
and
lead
to
warming
of
the
air
immediately
surrounding
them
(e.g.
carbon
black)
Mt
Pinatubo
(Philippines,
1991)
–
immediate
warming
followed
by
significant
cooling
(larger
parHcles
of
ash
fell
vs.
sulfur
dioxide
aerosols
with
lifeHme
of
several
years
reflected
sunlight
back
into
space
Global
warming
–
AllocaHon
to
Natural
and
Anthropogenic
Factors
Overall,
cooling
cancels
about
40%
of
warming
Greatest
uncertainty
Marine
phytoplankton
–
dimethyl
sulfide
emivers
–
DMS
is
oxidized
to
SO2
which
can
further
oxidize
to
H2SO4
and
CH3SO3H
–
both
of
which
lead
to
the
formaHon
of
water
droplets…
Cooling
due
to
changes
in
land
use
minus
warming
arising
from
deposiHon
of
sunlight‐absorbing
black
soot
on
snow
and
ice
5
10/7/10
Global
Warming
and
Geography
UncertainHes
in
Global
Climate
Change
• 
Low
lying
clouds
–
net
cooling
effect
• 
High
lying
clouds
–
net
warming
effect
•  century‐long
warming
or
cooling
trends
appear
once
or
twice
a
millenium;
80‐90%
likelihood
that
increase
in
the
20th
century
was
not
a
wholly
natural
climaHc
fluctuaHon
AddiHonal
signs
of
Global
Warming
•  winter
has
shortened
by
11
days
over
the
last
30
years
–
advent
of
spring
(budding
of
plants
and
flowering)
• 
start
of
autumn,
defined
by
the
date
at
which
leaves
change
color
–
delayed
by
5
days
• 
19
fewer
frost
days
in
the
western
United
States
and
3
fewer
in
the
eastern
part
• 
Glaciers,
polar
ice
caps
and
polar
sea
ice
are
melHng
at
unprecedented
rates
• 
10%
of
the
worlds
winter
snow
cover
has
disappeared
since
the
late
1960s
• 
95%
of
the
coral
reef
in
the
Seychelles
is
dead
Sulfate
aerosols
have
kept
the
eastern
porHons
of
North
America
cooler
–
a
temporary
effect
as
aerosols
have
a
much
shorter
lifeHme
than
CO2
ArcHc
has
warmed
most
of
all
–
sea
ice
is
disappearing
–
posiHve
feedback
–
ice
reflects
sunlight
more
than
liquid
water
(increased
evaporaHon
and
cloud
cover?)
• 
Mosquito‐born
diseases
are
now
observed
at
high
alHtudes
and
northern
laHtudes
(malaria
as
far
north
as
southern
Ontario;
West
Nile
now
ubiquitous
in
the
United
States
• 
Increased
precipitaHon
except
in
areas
just
N
and
S
of
the
equator
• 
Extreme
weather
is
becoming
more
common
Rising
Sea
Levels
6
10/7/10
hvp://www.olympus.co.jp/en/gww/kilimanjaro/movie.html
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10/7/10
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