Statistical Evidence in
Global Climate Change
R. Cary Tuckfield
Ecological Statistician
April 15, 2011
The Point:
• Global Climate Change is not the
issue
– it is happening, there is data, and it’s
complicated
• The anthropogenic cause?
– that’s the issue
What this talk isn’t…
• Comprehensive
• Finished
• Political
• Meteorological (I’m a statistician)
• Fanatical, or
• “Religical”
What it is…
• A review of some of the data
• An analysis of temperature trends
• One statistician's view (albeit an
ecological one) on what to make of it
The Meltdown
Disintegration of 1250 mi2
of the Larsen B Antarctic
ice shelf in 2002.
Dyurgerov and Meier (2005)
Figure 2. Worldwide average change is glacier thickness (cm/yr)
http://www.globalwarmingart.com/wiki/Image:Glacier_Mass_Balance_png
Receding Glacier:
3 Year Record
Columbia Glacier, AK
Oct. 5, 2007 – May 7, 2009
www.ExtremeIceSurvey.org
Zonal Mean Temp Anomaly (oC)
Is this warming trend
everywhere?
Latitude
from NASA GISS website (land stations only)
Biological Consequences
• Flowering plants are flowering earlier;
some not at all
• SRS Wood Ducks are nesting earlier in
the spring
• Wintering ranges for multiple bird
species now extend further northward
• Butterfly species diversity declining at
sea level, increasing at tree line
Earlier Flowering
Cardamine hirsuta
(42 d)
Ave. 1st flowering date
89 species
1970 – 1990
Duchesnea indica
(46 d)
Lamium purpureum
(39 d)
DC – Washington
CP – College Park, MD
Nyssa sylvatica
(35 d)
SRS Wood Ducks
Wood ducks
nesting activity at
SRS has advanced
by nearly 1 month
in a 23 year period,
early 70’s – mid
90’s.
Wintering Birds Range Extensions
Changes in Butterfly
Distribution
Parnassius clodius
• This butterfly,
(above) is now
found at higher
elevations in CA
Forister & Shapiro
2003 Global
Change Biol
Forister et al.
2010 PNAS
•
•
•
•
•
35 yrs
159 species
10 sites
0-2,775 ft elev
Sierra Nevada Mtns
• Overall,
diversity is
declining at
lower elevations
and increasing at
higher elevations
Space Studies (GISS)
• US: Land weather stations
only 1880-2007
• Global: Land & Ocean
weather stations
• Anomaly: Difference from
overall annual average
temperature
1.5
Tr
Pe
US
1
0.5
0
-0.5
1.5
-1
1
1870 1890 1910 1930 1950 1970 1990 2010
Anomaly oC
• NASA Goddard Institute for
(oC)
Anomaly
Average
Annualized
Annualized
AverageTemperature
Temperature Anomaly
(oC)
Anomaly
oC
Anomaly oC
GISS Surface Temperatures
0.5
0.6
T
P
Year
Tr
Pe
Global
0
0.4
-0.5
0.2
0-1
-0.2 1870 1890 1910 1930 1950 1970 1990 2010
Year
-0.4
1870 1890 1910 1930 1950 1970 1990 2010
Year
Year
Year
Hadley data set
• Met Office Hadley
Ocean weather
stations data
• 1850-2007
• “smoothed” regression
fit to show trends in
ecological time
Cubic Spline fit
0.4
Anomaly oC
• Global: Land &
Temp Anomaly (oC)
Centre, UK
0.6
0.2
0
-0.2
-0.4
-0.6
1840
1880
1920
Year
Year
1960
2000
Number of Stations (1000s)
World Data station profile
Record Length (yrs)
Years
Years
• Few stations with many years of data
• Today ~2,000 stations per global annual average
• > coverage of northern hemisphere
• Simple Linear
Regression (SLR)
models / trend period
• Differences in Slopes
apparent
0.6
Trend
Period 30 yrs
1880-1916
1917-1946
1947-1976
1977-2007
Global GISS
Anomaly oC
0.4
0.2
0
-0.2
-0.4
-0.6
1870 1890 1910 1930 1950 1970 1990 2010
Year
Trend
Period 30 yrs
1850-1879
1880-1916
1917-1946
1947-1976
1977-2007
0.6
0.4
Anomaly oC
• ~30 year trend periods
Annualized Average Temperature Anomaly (oC)
Short-term
Trends
Global Hadley
0.2
0
-0.2
-0.4
-0.6
1840
1880
1920
Year
Year
1960
2000
0.3
0.2
0.1
0.6
Linear Fit Data=="GISS"
Linear Fit Data=="Hadley"
0
-0.1
-0.2
-0.3
Linear Fit Data=="GISS"
Linear Fit Data=="Hadley"
0.5
Anomaly oC
Anomaly oC
Temperature Anomaly (oC)
Slopes: Statistical test results
0.4
0.3
0.2
0.1
-0.4
0
-0.5
-0.1
1915 1920 1925 1930 1935 1940 1945
Year
Year
1980
1985
1990
1995
2000
2005
Year
Year
• Rates of temperature increase for 1916H 0 : d  12  11  0 1945 and 1978-2007 are
indistinguishable
d ~ t n1  n2 2
• Rates not different between GISS and
Hadley datasets
• Overall rate = 1.6 oC / century
• 1961 – 1990 baseline
• Spline fits
• Both graphs presented
• But, the “mud” hit the
fan over the lower
panel
Northern Hemisphere Anomaly (oC)
Relative to 1961 to 1990
IPCC
“Brouhaha”
http://climateaudit.org/2009/12/10/ipccand-the-trick/
Year
Long-term Historical Trends
Medieval Warming Period
Little Ice Age
• Loehle 2007 Energy & Environment
• From 18 different non-treering
datasets
Is CO2 the culprit?
Left Scale:
Anomaly oC
Global GISS
Temperatures
Right Scale:
Mean
Annual CO2 (ppm)
380
0.5
370
0.4
0.3
360
0.2
350
0.1
340
0
330
-0.1
320
-0.2
310
1960
1970
1980
1990
2000
Year
Year
Figure 3. Overlay plot of the NASA GISS World temperature
Mean Annual CO2 (ppm)
Annual CO2 (ppm)
Mean
Anomaly (oC)
Temperature
Anomaly oC
0.6
390
Mauna Loa, HI Weather Station
CO2 Monitoring Sites
CO2 Concentration (ppm)
Eco-time trends in CO2
Point Barrow, AK
• Same scale on X- &
Y-axes
• Monotonic + trend
• > Variation within &
between stations
http://cdiac.ornl.gov/trends/co2/
Mauna Loa, HI
South Pole, Anarctica
Year
Polar Perspectives
Could annual CO2 cycling have to do
with seasonal photosynthetic output?
Quaternary CO2 Trends
Same Period: With
Concomitant Data
Evolutionary time trends in CO2
•
Rothman 2002 PNAS
87Sr/86SR
pCO2(t) / pCO2(0)
isotopic
ratio is highly
correlated with
inorganic-organic
13C/12C isotope ratio
• Co-dependent on
weathering &
magmatic processes
Time (106 yrs BP)
• Partial pressure in
Conclusion:
atmospheric CO2
Atmospheric CO2 un-related
inferred from ratio
to climatic conditions
fluctuations
Findings
• Global surface temps show
– Variable short-term trends – + rates & - rates
– Millennial & evolutionary cycles in warming/cooling
• CO2 is monotonically increasing over relatively
short time periods, but temp doesn’t
• CO2 concentration shows constant annual &
Cenozoic cycling
• CO2 cycles have higher amplitude in northern
hemisphere
So, In Summary
• Climate change is always occurring
• Global surface temperature is
recently (<50 yrs) and positively
correlated with atmospheric CO2
• Historically, temperatures were as
high or higher than now
• Pre-historically, CO2 and
temperature seem more correlated to
geochemical processes
What to do?
• Is it wise to act without certain
knowledge?
• How do we know whether IPCC’s
recommendations will work?
• What are the consequences if we do
nothing?
• Or, something that doesn’t work?
No Easy Answers
• Not all scientists are in agreement
• Some data support the anthropogenic
hypothesis, some don’t
• Some things just can’t be measured well,
or at all
• Consequently, Global Warming has
become a political issue
• It is a matter of interpretation and belief
(given the data and funding, respectively)
Take Home Message
• Personal decision is the right of citizenship –
data are usually helpful
• Find out what the data are “saying”
• But convincing evidence is a matter of
judgment and opinion
Remember, in a democratic republic, citizen opinion (i.e. the
vote) “trumps” science, whether they are in agreement or
not. In the rest of the world, well,…that’s another matter.