Measuring Climate ChangeRob 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 ofclimate elements (such as temperature, pressure, or winds) sustained overseveral 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 · ε · σ · T 4

What goes in...

S · πr 2(1− a) = 4πr 2 · ε · 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 · ε · σ · T 4

• ε is the emissivity (transparency of atmosphere)

• σ is the Stefan-Boltzman constant

• T is temperature

Conservation of Energy

T 4 =S(1− a)

4ε · σ• Plug in actual a, σ, ε,S , get T = 14.8◦C (58◦F )

• Start changing stuff:• 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 ε 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!

T 4 =S(1− a)

4ε · σ

if ε = 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...

(source: IPCC AR5 2014)

... 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 averagetemperatures since the mid-20th century is very

likely due to the observed increase in anthropogenicgreenhouse gas concentrations.”

In 2014:

“It is extremely likely that human influence has beenthe dominant cause of the observed warming sincethe 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 toHumans?

How Does the IPCC Attribute the Change toHumans?

How Does the IPCC Attribute the Change toHumans?

How Does the IPCC Attribute the Change toHumans?

1. Discretize space on earth (≈ 66, 000 grid cells on surface, times 20layers 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 equationsin discretized time and space.

4. Run under 4 different emissions scenarios of atmospheric CO2.

How Does the IPCC Attribute the Change toHumans?

How Does the IPCC Attribute the Change toHumans?

(source: IPCC AR5 2014)

How Does the IPCC Attribute the Change toHumans?

(source: IPCC AR5 2014)

How Does the IPCC Attribute the Change toHumans?

(source: IPCC AR5 2014)

How Does the IPCC Attribute the Change toHumans?

(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 DougNychka 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