Measuring Climate Change
Rob Erhardt, Wake Forest University
SUS 602 Analytics, January 2015
Weather and Climate
“Climate is what you expect, weather is what you get.” Robert Heinlein.
(image: Najavo Nation, New Mexico)
Weather and Climate
Climate change is “any systematic change in the long-term statistics of
climate elements (such as temperature, pressure, or winds) sustained over
several decades or longer.” American Meteorological Association.
(image: Glacier National Park)
Weather and Climate
“Climate is the distribution of weather.”
American Statistical Association, 2010.
Weather and Climate
Energy:
S · πr 2(1 − a) = 4πr 2 · · σ · T 4
What goes in...
S · πr 2(1 − a) = 4πr 2 · · σ · T 4
• S = 1360 W /m2 is the solar constant.
• r = 6400 km is the radius of the earth
• a is the earth’s albedo (reflectivity)
... must go out.
S · πr 2(1 − a) = 4πr 2 · · σ · T 4
• is the emissivity (transparency of atmosphere)
• σ is the Stefan-Boltzman constant
• T is temperature
Conservation of Energy
T4 =
S(1 − a)
4 · σ
• Plug in actual a, σ, , S, get T = 14.8◦ C
• Start changing stuff:
(58◦ F )
• If S went up 1%, T goes up 0.7◦ C (1.3◦ F )
• If a went down 1%, T goes up 0.3◦ C (0.55◦ F )
• If went down 1%, T goes up 0.7◦ C (1.3◦ F )
Why Would the Albedo Change?
Why Would the Albedo Change?
Rondonia, Brazil in 1975, 1989, 2001
Why Would the Albedo Change?
(source: NASA/Goddard Space Flight Center)
Why Would the Albedo Change?
Why Would the Emissivity Change?
(source: NASA)
Fun Fact!
T4 =
S(1 − a)
4 · σ
if = 1 average global temperature would be ≈ −1◦ F
Where does data come from?
(source: National Center for Atmospheric Research)
Where does data come from?
(source: NASA)
Where does data come from?
Who oversees this science?
(www.ipcc.ch)
Global surface temperatures have been rising...
... sea levels have been rising...
(source: IPCC AR4 2007)
... and glaciers have been retreating.
(source: IPCC AR4 2007)
(and there’s much more in the reports).
In 2007:
“Warming of the climate system is unequivocal.”
“Most of the observed increase in global average
temperatures since the mid-20th century is very
likely due to the observed increase in anthropogenic
greenhouse gas concentrations.”
In 2014:
“It is extremely likely that human influence has been
the dominant cause of the observed warming since
the mid-20th century.”
[WGI AR5 SPM Section D.3, 2.2, 6.3, 10.3-6, 10.9]
How Does the IPCC Attribute the Change to
Humans?
How Does the IPCC Attribute the Change to
Humans?
How Does the IPCC Attribute the Change to
Humans?
How Does the IPCC Attribute the Change to
Humans?
1. Discretize space on earth (≈ 66, 000 grid cells on surface, times 20
layers is 1.32 million cells.)
2. Discretize time to 3-hour intervals (8 per day, 2920 per year)
3. Model relationship of climate variables (temperature, pressure, wind,
atmospheric carbon content, etc.) as partial differential equations
in discretized time and space.
4. Run under 4 different emissions scenarios of atmospheric CO2.
How Does the IPCC Attribute the Change to
Humans?
How Does the IPCC Attribute the Change to
Humans?
(source: IPCC AR5 2014)
How Does the IPCC Attribute the Change to
Humans?
(source: IPCC AR5 2014)
How Does the IPCC Attribute the Change to
Humans?
(source: IPCC AR5 2014)
How Does the IPCC Attribute the Change to
Humans?
(source: IPCC AR5 2014)
Virginia and North Carolina Coasts
Virginia and North Carolina Coasts
Virginia and North Carolina Coasts
Virginia and North Carolina Coasts
Thanks.
Acknowledgments: Some images and slides were provided by Doug
Nychka at NCAR and Peter Guttorp at U-Washington.
Current Research: Single Event Attribution
Source: NASA Earth Observatory
Current Research: Single Event Attribution
Current Research: Single Event Attribution
Source: European Space Agency, July 29 2010
Current Research: Single Event Attribution
Current Research: Single Event Attribution