EarthWeek 2008:
The Future of Utah
Principal Research Scientist
The University of Alabama In Huntsville
April 24, 2008
Roy W. Spencer, Ph.D
Global Warming:
Some Reasons for Optimism
– Mostly Mankind?..or…
– Mostly Nature?
• But WHY has it warmed?
– (There are no “global warming deniers”)
• We HAVE experienced global warming.
The Big Picture…
Atmospheric Warming (deg. Celsius)
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
90
91
92
93
94
95
96
97
Mt. Pinatubo
Cooling
El Nino
Warming
98
99 2000 2001 02
04
YEAR
03
05
(through Feb. 2008)
06
07
08
09
10
11
12
13
* Surface to 8 miles altitude
February
2008
14
15
1979-1998 Average
U.N. IPCC Projection
of Future Warming
Globally Averaged Satellite-Based Temperature
of the Lower Atmosphere*
Due to Nature, Global Temperatures Vary GREATLY
from Year to Year…
16
Degrees C
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
0
100
200
300
400
Dr. Craig Loehle (2007)
(average of 18
non-tree ring proxies,
data years AD 1 - 1995)
500
600
700
800
Little Ice Age
CO2 from Law Dome Ice Core
End of Viking
Colonization of
Greenland
End of Viking
colonization of
Greenland
UK Met Office & U. of E. Anglia
(thermometers,
data years 1850-2007)
YEAR (A.D.)
R. W. Spencer, 2007
900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000
Vikings arrive
in Greenland
Medieval Warm Period
(30-year averages, last data year 2007)
2000 Years of Global Temperatures
(with or without mankind’s help)
…and from one century to the next!
..Ice core relationship should NOT but used as evidence that
CO2 changes cause temperature changes!
BUT…Temperature Changes Preceded CO2 Changes
by ~ 1,000 Years, so…
Al Gore’s Persuasive Vostok Ice Core Record of
The Connection between CO2 and Temperature
Emitted Infrared Radiation
Global average input = output =
≈235 Watts per square meter
=
=> Greenhouse gases (e.g. carbon dioxide) affect Infrared Radiation
Absorbed Sunlight
“GLOBAL WARMING” BASICS: GW theory is all about mankind
“disrupting” the Infrared part of Earth’s energy balance
(Colored bar areas
proportional to
energy fluxes)
Absorbed
Sunlight
≈235 W/m2
Estimated
imbalance from
manmade
influences
(GHG’s, aerosols)
≈1 W/m2
How much humans
have perturbed Earth’s
assumed 235 W/m2
energy balance
Earth
Atmosphere
Emitted
Infrared
≈235 W/m2
2000
2020
2040
2060 “negative
2080
2100
feedback”
YEAR
hi cld
/
ld
c
w
lo
+
r/
o
p
CO2/ - va
s
d
+
u
r
o
lo
c
p
“positive
a
h
v
g
i
e
h
r
o
e
feedback”
r
m
o
r
2+ s+m
o
p
O
a
C oud
rv
e
t
a
l
w
c
e
r
w
o
m
lo
r
+
e
2
CO
nly
o
fe w
2
O
C
Future Warming Depends Mostly Upon
How Clouds and Water Vapor Will Respond
to the Small Amount of CO2 Warming
<1oF
2o – 3oF
4o – 6oF
6o – 10o F
Projected
Warming
warm, humid air
Boundary layer
evaporation
removes heat
Ocean or Land
cool, dry air
Sunlight absorbed
at surface
Heat
NATURES AIR CONDITIONER:
released through
Most of our atmosphere is being continuously
condensation
causes air to rise, recycled by precipitation systems, which then
determines the strength of the Greenhouse Effect
rain falls to surface
Cooling (loss of IR radiation)
by dry air to space
– Daily random cloud cover variations can cause SST variability that
“looks like” positive cloud feedback
• Spencer & Braswell, 2008: Potential Biases in Feedback
Diagnosis from Observational Data: A Simple Model
Demonstration, J. Climate (in press).
– A composite of the 15 strongest tropical intraseasonal
oscillations during 2000-2005 show strong negative cloud
feedback (Lindzen’s “Infrared Iris”)
• Spencer, Braswell, Christy, & Hnilo, 2007: Cloud and
Radiation Budget Changes Associated with Tropical
Intraseasonal Oscillations, Geophysical Research
Letters, August 9.
Recent Research Supporting NEGATIVE Feedback
Predicted Warming by 2100 (deg. C)
0
1
2
3
4
5
6
0
0.1
Theoretical (NO feedbacks)
(Forster & Gregory, 2006 J. Climate)
0.2
0.4
0.5
0.6
0.7
0.8
1
1.1
Climate Sensitivity (deg. C / [watts per sq. meter])
0.3
(Spencer et al., Aug. 2007 GRL)
0.9
Observations (inter-annual variability)
Observations (intra-seasonal variability)
(Spencer & Braswell,
2008 J. Climate,
cond. accepted)
Potential Error from
Improper Diagnosis
of Observations
(Forster & Taylor ,
2006 J. Climate)
U.N. IPCC
Climate Models
Global Warming by 2100
as a function of "Climate Sensitivity"
1.2
1.3
1.4
How Do the Observational Estimates of Feedback
Compare to Climate Models?
So….if mankind hasn’t caused
global warming….what has?
T Anomaly (deg. C)
SOI Index
PDO Index
OCEAN
ONLY
b. Southern Oscillation Index, 1902-2006
LAND +
OCEAN
a. Global Mean Temperature, 1902-2006
c. Pacific Decadal Oscillation, 1902-2006
YEAR
1902 1912 1922 1932 1942 1952 1962 1972 1982 1992 2002
-1.6
-2
-0.8
-1.2
-0.4
0.4
0
1.2
0.8
1.6
2
1902 1912 1922 1932 1942 1952 1962 1972 1982 1992 2002
2
1.6
1.2
0.8
0
0.4
-0.4
-0.8
-1.2
-1.6
1902 1912 1922 1932 1942 1952 1962 1972 1982 1992 2002
-2
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
Pacific Decadal
Oscillation Index
Southern
Oscillation Index
(El Nino / La Nina)
Global avg.
temperature
…how about Mother Nature?
Radiative Forcing (W/m )
2
T Anomaly (deg. C)
-0.6
1902
-0.4
-0.5
-0.3
-0.2
0.0
-0.1
0.1
0.2
0.3
0.41902
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
1922
1932 1942
1922 1932 1942
1962 1972
YEAR
1952
1962
1982
1992
2002
1972 1982
1992
2002
Model Trend
o
+0.50 /century
Observed Trend
o
+0.69 /century
YEAR
1952
SOI + PDO Forcing of Model
r = 0.94
1912
b.
1912
a.
1,000 m deep ocean;
no feedback
Simple Climate Model Driven by
Assumed Natural Cloud Variations
3. Climate models produce too much warming, probably
because researchers confuse cause and effect when
analyzing natural climate variability.
2. It is NOT known with any level of certainty how much of
the warming is manmade versus natural
1. Global warming HAS occurred over the last 150 years or
so…just like it has occurred before.
Conclusions
• Only wealthy countries can afford the research
• How do countries maintain that wealth? (a healthy economy)
– Conservation will have almost no effect
– Future use of solar, wind, etc, will increase rapidly,
but will remain a small percentage of humanity’s
energy needs.
– Transition to more nuclear power could help some
– Need NEW energy technology (at least 30-40 years
away)
• Sure….if it was relatively painless (it’s not)
• Only solution (if one is needed) is through new
energy technologies.
But…if catastrophic warming is even possible,
shouldn’t we “do something”?