Climate Change, Texas, and the Limits of Confidence Change, Texas, and the Limits of Confidence John Nielsen-Gammon Dept. of Atmospheric Sciences Texas A&M University

Climate Change, Texas, and

the Limits of Confidence

John Nielsen-Gammon

Dept. of Atmospheric Sciences

Texas A&M University

Global Surface Temperature (3)

Pattern of Temperature Trend

Regional Temperatures, 1-2000

(PAGES 2013)

Multiple datasets & analyses

(AR5 WG1 FAQ2.1)

Mass change, ice sheets

(AR5 WG1 Figs 4.13d-4.14d)

Changes in Water and Ice

(AR5 WG1 FAQ2.1)

Global Surface Temperature (3)

Global temperatures

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1850 1880 1910 1940 1970 2000 2030

GlobalSurfaceTemperatureAnomalies(°C)BasePeriod:1980-1999

HadCRUTsurface

GISTEMPsurface

NGTsurface

BESTsurface

RCP8.5avg

Global temperatures

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1850 1880 1910 1940 1970 2000 2030


HadCRUTsurface

GISTEMPsurface

NGTsurface

BESTsurface

RCP8.5avg

Global Energy Balance, Part 1

Sun

Atmosphere

Each arrow = 20 W/m2

Earth

Scientific Principles

• Energy Imbalance implies a net gain or

loss of energy

• Typical annually averaged energy

imbalances are << 1% of the energy

flow


Sun

Atmosphere


Earth


Sun

Atmosphere


Earth


Sun

Atmosphere

Earth



Sun

Atmosphere

Earth



Sun

Atmosphere

Earth



Sun

Atmosphere

Earth



Sun

Atmosphere

Earth



Sun

Atmosphere

Earth



Sun

Atmosphere

Earth



Sun

Atmosphere

Earth

To maintain heat flow

into atmosphere, Earth

must warm too

Detection and Attribution

• Identify trend: detection

• Compare with distinct patterns in space

and time caused by different forcing

agents

• Apportion role of different forcing

agents: attribution

Evolution of Estimated Forcings

(AR5 WG1 Fig. 8.18)

Global temperatures

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1850 1880 1910 1940 1970 2000 2030


HadCRUTsurface

GISTEMPsurface

NGTsurface

BESTsurface

RCP8.5avg

Texas vs Globe

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1850 1880 1910 1940 1970 2000 2030


HadCRUTsurface

GISTEMPsurface

NGTsurface

BESTsurface

RCP8.5avg

Texas

Texas 5-yr Avg vs Globe

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1850 1880 1910 1940 1970 2000 2030


HadCRUTsurface

GISTEMPsurface

NGTsurface

BESTsurface

RCP8.5avg

Texas5yr

Extreme Weather

• Short definition: Weather that’s

newsworthy

• Long definition: two kinds

– Weather that’s extremely unlikely

– Weather that’s unhealthy or damaging

– (The same event often fits both definitions)

Melissa Phillip, Houston Chronicle

0

1

2

3

4

5

6

7

8

9

Rainfall(inches)

WallerCounty-Average1-DayRainfall(since1950)

0

1

2

3

4

5

6

7

8

9

Rainfall(inches)


April 18, 2016

0

1

2

3

4

5

6

7

8

9

Rainfall(inches)


August 28, 2017

0

1

2

3

4

5

6

7

8

9

Rainfall(inches)


August 28, 2017

August 29, 2017

Example #1: Heat and Cold

IPCC SREX

The Three Pillars of Sound

Attribution


Attribution

A clear

historical

trend


Attribution

A clear

historical

trend

Consistent

model

projection

s


Attribution

A clear

historical

trend

A sound

physical

basis

Consistent

model

projection

s

Example #2: Heavy Rain

The Faucet

• Climate change’s

thermodynamic impact:

the size of the pipe

+ 7% per °C

• Climate change’s

dynamic impact: turning

the handle

The Faucet

• The size of the pipe

matters most when the

faucet is wide open

99.98th%ile(14-yrreturnperiod)ChangeinFrequency

0.0xto0.11x

0.11xto0.25x

0.25xto0.43x

0.43xto0.67x

0.67xto1.0x

1.0xto1.5x

1.5xto2.3x

2.3xto4x

4xto9x

95% confidence interval using effective degrees of freedom estimated following D. A. Griffith &

Z. Zhang (1999): Computational Simplifications Needed for Efficient Implementation of Spatial

Statistical Techniques in a GIS, Geographic Information Sciences, 5:2, 97-105, DOI:

10.1080/10824009909480519

0

0.2

0.4

0.6

0.8

1

0 20 40 60 80 100

Frequency(eventsperdecade)Example:20%increase

20% increase ~ 30% trend

Arid

W

et

0.00 5.00 10.00 15.00 20.00 25.00

Harvey2017

Beulah1967

NCSep2010

Georges1998

Alex2010

AverageFiveDayRainfall,50,000sq.mi.

0.00 10.00 20.00 30.00 40.00 50.00

Harvey2017

LAAug1940

TXJun1899

Beulah1967

Claude e1979


0.00 10.00 20.00 30.00 40.00 50.00

Harvey2017

LAAug1940

TXJun1899

Beulah1967

Claude e1979


Harris

Coun

ty: 3

4”

Example #3: Hurricanes

Hurricanes: The Balance of

Evidence

• Increase in peak intensity (1.5 pillars)

• Decrease in frequency (1 pillar)

– …but spatially variable (1.5 pillars)

Did Harvey stall because of

climate change?

20

22

24

26

28

30

32

34

36

38

40

-100 -95 -90 -85 -80 -75

Lat

H4Harvey2017Aug

TSAllison2001Jun

TSAllison1989Jun

TS1908#4Jul

H1Juan1985Oct

2005

TSAlberto1994

H31871#3Aug

1980

1941

1938

1953

H11904#1Oct

Coast

Resources

• IPCC.ch

– Special report on extremes (SREX)

– Fifth assessment report, working group 1

(AR5 WG1)

• National climate assessment

• News items

– AP + USA TODAY + NYTIMES ~ Network

news

Summary

• The climate is changing

• Over the long haul, it’s us

• Future changes are hard to pin down

• Some impacts are easy

– It’ll get warmer, it’ll rain harder

• Some impacts are hard

– More droughts? Fewer hurricanes?

Contact Information

• John W. Nielsen-Gammon

• [email protected]

• 979-862-2248

• http://climatexas.tamu.edu

mailto:[email protected]



Climate Change, Texas, and the Limits of Confidence Change, Texas, and the Limits of Confidence John Nielsen-Gammon Dept. of Atmospheric Sciences Texas A&M University

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