Extreme Weather, Climate Change, and Harvey

John W. Nielsen-Gammon, Texas A&M UniversityTexas State Climatologist

-8

-6

-4

-2

0

2

4

6

8

1895 1915 1935 1955 1975 1995 2015Diffe

rencefrom

20thCe

nturyAv

erage(°F)

UpperCoastSeasonalTemperatureAnomalies

Tmax+&solid,Tmin-&doGed

DJF MAM JJA SON DJF MAM JJA SON

DJF MAM JJA SON DJF MAM JJA SON

Basis of Climate Prediction

• Past observed changes• Climate model projections• Basic physical understanding of climate

system

Three out of three

• Higher temperatures– More extreme highs– Fewer extreme lows

• Extreme rainfall– More extreme rain– More dry days, droughts

• Sea level rise

-1

-0.5

0

0.5

1

1.5

2

1850 1880 1910 1940 1970 2000 2030 2060

GlobalSurfaceTemperatureAnomalies(°C)BasePeriod:1980-1999

HadCRUTsurface

GISTEMPsurface

NGTsurface

BESTsurface

RCP8.5avg

Texas5yr

+4.5 °F

+3.4 °F

+2.2 °F

+1.1 °F

0 °F

-1.1 °F

IPCC sensitivity range

Lewis & Curry range

Average model output

Local increase?

5-year Average Texas Temperatures

John Nielsen-Gammon, Texas A&M University 6

Harvey and Climate Change

• Existence? Doubtful influence• Storm track? Unknown influence• Intensity? Possible influence• Precipitation? Enhancement

0

5

10

15

20

25Av

erageRa

infall(in

ches)

Historic analyses: Applied Weather Associates; US Army Corps of Engineers

John Nielsen-Gammon, Texas A&M University 8

0

5

10

15

20

25Av

erageRa

infall(in

ches)

33.28”

Historic analyses: Applied Weather Associates; US Army Corps of Engineers

John Nielsen-Gammon, Texas A&M University 9

Area\Duration 2Days 3Days 4Days 5Days

1,000sq miLouisiana,August1940 Harvey Harvey Harvey

2,000sq mi Harvey Harvey Harvey Harvey

5,000sq mi Harvey Harvey Harvey Harvey

10,000sq mi Harvey Harvey Harvey Harvey

20,000sq mi Harvey Harvey Harvey Harvey

50,000sq mi Harvey Harvey Harvey Harvey

(Central/Eastern) US Depth-Area-Duration All-Time Records

John Nielsen-Gammon, Texas A&M University 10

0

5

10

15

20

25

30

AverageRa

infall(in

ches)

Historic analyses: Applied Weather AssociatesJohn Nielsen-Gammon, Texas A&M University

11

0

5

10

15

20

25

30

AverageRa

infall(in

ches)

Historic analyses: Applied Weather AssociatesJohn Nielsen-Gammon, Texas A&M University

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Climate change rainfall contribution?

0

5

10

15

20

25

30

AverageRa

infall(in

ches)

Historic analyses: Applied Weather AssociatesJohn Nielsen-Gammon, Texas A&M University

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Climate change rainfall contribution?100,000 homes?

10,000 homes?

1,000 homes?