Eugene S. TakleProfessor

Department of AgronomyDepartment of Geological and Atmospheric Science

Director, Climate Science ProgramIowa State University

Ames, IA 50011

gstakle@iastate.edu

Diagnosis of the US Drought of 2012:

Climate Change, Agriculture, and Drought: Lessons from the 2012 Growing Season

Historical Perspective: Relevant Recent Climate

Conditions

Iowa State-Wide Average Data

19701972

19741976

19781980

19821984

19861988

19901992

19941996

19982000

20022004

20062008

20102012

0

2

4

6

8

10

12

14

Number of Days with a Maximum Temperature Greater Than or Equal to 100°F

Year

Num

ber o

f Day

s

Des Moines, Iowa Airport Data

1974: 71977: 8

1983: 13

1988: 10

19701972

19741976

19781980

19821984

19861988

19901992

19941996

19982000

20022004

20062008

20102012

0

2

4

6

8

10

12

14

Number of Days with a Maximum Temperature Greater Than or Equal to 100°F

Year

Num

ber o

f Day

s 1974: 71977: 8

1983: 13

1988: 10

6 days ≥ 100oF in 23 years

Des Moines, Iowa Airport Data

19701972

19741976

19781980

19821984

19861988

19901992

19941996

19982000

20022004

20062008

20102012

0

2

4

6

8

10

12

14

Number of Days with a Maximum Temperature Greater Than or Equal to 100°F

Year

Num

ber o

f Day

s 1974: 71977: 8

1983: 13

1988: 1011 days in 2012

6 days ≥ 100oF in 23 years

Des Moines, Iowa Airport Data

19701972

19741976

19781980

19821984

19861988

19901992

19941996

19982000

20022004

20062008

20102012

0.0

5.0

10.0

15.0

20.0

25.0

R² = 0.0354248508187915

Winter Average State-Wide Temperature Minimum

Year

Min

Tem

pera

ture

(°F)

19701972

19741976

19781980

19821984

19861988

19901992

19941996

19982000

20022004

20062008

20102012

15.0

20.0

25.0

30.0

35.0

40.0

45.0

R² = 0.013473121517232

Winter Average State-Wide Temperature Maximum

Year

Max

Tem

pera

ture

(°F)

19701972

19741976

19781980

19821984

19861988

19901992

19941996

19982000

20022004

20062008

20102012

70.0

75.0

80.0

85.0

90.0

95.0

R² = 0.0574177778298495

Summer Average State-Wide Temperature Maximum

Year

Max

Tem

pera

ture

(°F)

19701972

19741976

19781980

19821984

19861988

19901992

19941996

19982000

20022004

20062008

20102012

52.0

54.0

56.0

58.0

60.0

62.0

64.0

66.0

R² = 0.0382239214204405

Summer Average State-Wide Temperature Minimum

Year

Min

Tem

pera

ture

(°F)

19701972

19741976

19781980

19821984

19861988

19901992

19941996

19982000

20022004

20062008

20102012

0.0

5.0

10.0

15.0

20.0

25.0

R² = 0.0354248508187915

Winter Average State-Wide Temperature Minimum

Year

Min

Tem

pera

ture

(°F)

19701972

19741976

19781980

19821984

19861988

19901992

19941996

19982000

20022004

20062008

20102012

15.0

20.0

25.0

30.0

35.0

40.0

45.0

R² = 0.0134731215172317

Winter Average State-Wide Temperature Maximum

Year

Max

Tem

pera

ture

(°F)

19701972

19741976

19781980

19821984

19861988

19901992

19941996

19982000

20022004

20062008

20102012

70.0

75.0

80.0

85.0

90.0

95.0

R² = 0.057417777829848

Summer Average State-Wide Temperature Maximum

Year

Max

Tem

pera

ture

(°F)

19701972

19741976

19781980

19821984

19861988

19901992

19941996

19982000

20022004

20062008

20102012

52.0

54.0

56.0

58.0

60.0

62.0

64.0

66.0

R² = 0.0382239214204407

Summer Average State-Wide Temperature Minimum

Year

Min

Tem

pera

ture

(°F)

Iowa State-Wide Average Data

18701877188418911898190519121919192619331940194719541961196819751982198919962003201010.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

R² = 0.010782029618847

Total Annual State-Wide Average Precipitation

Year

Tota

l Ave

rage

Pre

cipi

tatio

n (in

ches

)

Iowa State-Wide Average Data

18701877188418911898190519121919192619331940194719541961196819751982198919962003201010.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

R² = 0.010782029618847

Total Annual State-Wide Average Precipitation

Year

Tota

l Ave

rage

Pre

cipi

tatio

n (in

ches

) 1 yearTotals above 40”

5 years

Iowa State-Wide Average Data

18701877188418911898190519121919192619331940194719541961196819751982198919962003201010.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

R² = 0.010782029618847

Total Annual State-Wide Average Precipitation

Year

Tota

l Ave

rage

Pre

cipi

tatio

n (in

ches

)

1990-2011 highly favorable precip for crops

Cedar Rapids, Iowa Data

1890189619021908191419201926193219381944195019561962196819741980198619921998200420100

10

20

30

40

50

60

70

R² = 0.185027251740679

Cedar Rapids Total Annual Precipitation (inches)

Year

Tota

l Pre

cipi

tatio

n (in

ches

)

1890189619021908191419201926193219381944195019561962196819741980198619921998200420100

10

20

30

40

50

60

70

R² = 0.185027251740679

Cedar Rapids Total Annual Precipitation (inches)

Year

Tota

l Pre

cipi

tatio

n (in

ches

)

28.0” 39% increase 39.0”

Cedar Rapids, Iowa Data

1890189619021908191419201926193219381944195019561962196819741980198619921998200420100

10

20

30

40

50

60

70

R² = 0.185027251740679

Cedar Rapids Total Annual Precipitation (inches)

Year

Tota

l Pre

cipi

tatio

n (in

ches

)

Years with more than 40 inches

2

18

Cedar Rapids, Iowa Data

“One of the clearest trends in the United States observational record is an increasing frequency and intensity of heavy precipitation events… Over the last century there was a 50% increase in the frequency of days with precipitation over 101.6 mm (four inches) in the upper midwestern U.S.; this trend is statistically significant “

Karl, T. R., J. M. Melillo, and T. C. Peterson, (eds.), 2009: Global Climate Change Impacts in the United States. Cambridge University Press, 2009, 196pp.

Cedar Rapids, Iowa Data

1890189619021908191419201926193219381944195019561962196819741980198619921998200420100

2

4

6

8

10

12

14

Cedar Rapids PrecipitationDays per Year with Greater Than or Equal to 1.25 inches

Year

Num

ber o

f Day

s

Cedar Rapids, Iowa Data

1890189619021908191419201926193219381944195019561962196819741980198619921998200420100

2

4

6

8

10

12

14

Cedar Rapids PrecipitationDays per Year with Greater Than or Equal to 1.25 inches

Year

Num

ber o

f Day

s

Creates runoff

Cedar Rapids, Iowa Data

1890189619021908191419201926193219381944195019561962196819741980198619921998200420100

2

4

6

8

10

12

14

Cedar Rapids PrecipitationDays per Year with Greater Than or Equal to 1.25 inches

Year

Num

ber o

f Day

s

3.6 days 6.1 days69% increase

1890189619021908191419201926193219381944195019561962196819741980198619921998200420100

2

4

6

8

10

12

14

Cedar Rapids PrecipitationDays per Year with Greater Than or Equal to 1.25 inches

Year

Num

ber o

f Day

s

Number of Years with More than 8 Occurrences

0 9

Cedar Rapids, Iowa Data

Amplification of the Seasonality of PrecipitationSpring

WinterSummer

Fall

21.2 => 25.3 inches (22% increase) 12.1 => 10.5 inches (13% decrease)

Amplification of the Seasonality of PrecipitationSpring

WinterSummer

Fall

2012 1988

1988 wasHotter inAugust

2012 1988

Precip

Stress

Normal 2012 Normal 1988

NormalNormal

2012 1988

Accumdeficit

Accumstress

2012 1988

1988 wasHotter inAugust

2012 1988

Precip

Stress

Normal 2012 Normal 1988

NormalNormal

2012 1988

Accumstress

12 inches (30 cm) below normal

going into 2013

Mean Summer (JJA) Dew-Point Temperatures for Des Moines, IA

Rise of 3oF in 42 years

12% rise in water content in 42 years

19701972

19741976

19781980

19821984

19861988

19901992

19941996

19982000

20022004

20062008

20102012

52.0

54.0

56.0

58.0

60.0

62.0

64.0

66.0

R² = 0.0382239214204407

Summer Average State-Wide Temperature Minimum

Year

Min

Tem

pera

ture

(°F)

Iowa Statewide Summer Minimum Daily

Temperature

Illinois Yield Decline with Increasing Minimum Daily

Temperature during Grain-Fill Period

Illinois Decline of Length of Grain-Fill Period with Increasing Minimum Daily Temperature

High nighttime temperatures reduce the length of the grain filling period Extreme high temperatures during pollination Changes in planting dates due to wet soils Increased damage due to pests and pathogens resulting from pest overwintering in antecedent warmer winters and/or higher July-August humidity

Yield declines from potential are caused by many factors in addition to reduced precipitation

2012 Anecdotes from Iowa Producers

Dewfall may have contributed to soil moisture (moist rings observed in soil around plant stem that persists into mid-morning hours)

Pattern subsurface drainage tile may be drying out high locations in fields (high-yielding well drained areas have lowest yields)

2012 Anecdotes from Iowa Producers

Fields with corn-after-corn had reduced yields

Extremely dry conditions exposed differences in management (tillage methods, residue management, planting dates)

2012 Anecdotes from Iowa Producers

High within-field variability (soils, other); 0-200 bu/acre on one combine round

Most producers were expecting yields to be much lower and were pleasantly surprised at harvest

Iowa Agricultural Producers are Adapting to Climate Change:

Longer growing season: plant earlier, plant longer season hybrids, harvest later

Wetter springs: larger machinery enables planting in smaller weather windows

More summer precipitation: higher planting densities for higher yields Wetter springs and summers: more subsurface drainage tile is being

installed, closer spacing, sloped surfaces Fewer extreme heat events: higher planting densities, fewer pollination

failures Higher humidity: more spraying for pathogens favored by moist

conditions. more problems with fall crop dry-down, wider bean heads for faster harvest due to shorter harvest period during the daytime.

Drier autumns: delay harvest to take advantage of natural dry-down conditions, thereby reducing fuel costs

So what about droughts in the future?

Iowa State-Wide Average Data

18701877188418911898190519121919192619331940194719541961196819751982198919962003201010.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

R² = 0.010782029618847

Total Annual State-Wide Average Precipitation

Year

Tota

l Ave

rage

Pre

cipi

tatio

n (in

ches

) 1 yearTotals above 40”

5 years

Iowa State-Wide Average Data

18701877188418911898190519121919192619331940194719541961196819751982198919962003201010.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

R² = 0.010782029618847

Total Annual State-Wide Average Precipitation

Year

Tota

l Ave

rage

Pre

cipi

tatio

n (in

ches

) 1 yearTotals above 40”

7 years3 years

5 years

Totals below 25”2012

Projected Future Variability in Growing Season Precipitation for Iowa

More extreme high precip years

More extreme low precip years

CJ Anderson, ISU

Future Variability in Growing Season Precipitation for Iowa

More extreme high precip years

More extreme low precip years

CJ Anderson, ISU

Lines drawn by eye

Summary

The climate of 1990-2011 has been highly favorable for agriculture in Iowa and the US Midwest

Higher precipitation of the last 40 years has suppressed Iowa daily max temperatures in summer; dry summers in the future will unmask underlying climate warming trend

Frequency of precipitation extremes has increased

Recent trends and future projections suggest higher frequency of both floods and droughts

For More Information:

Climate Science ProgramIowa State University

http://climate.engineering.iastate.edu/http://www.meteor.iastate.edu/faculty/takle/

gstakle@iastate.edu

Acknowledgements: R Elmore for producer comments; discussions with C J Anderson, S E Taylor