Diagnosis of the US Drought of 2012:

1. Diagnosis of the US Drought of 2012: Eugene S. Takle Professor Department of Agronomy Department of Geological and Atmospheric Science Director, Climate Science Program Iowa State University Ames, IA 50011 gstakle@iastate.edu Climate Change, Agriculture, and Drought: Lessons from the 2012 Growing Season

2. Historical Perspective: Relevant Recent Climate Conditions

3. Iowa State-Wide Average Data

4. Des Moines, Iowa Airport Data 1983: 13 1988: 10 1977: 8 1974: 7

5. Des Moines, Iowa Airport Data 1983: 13 1988: 10 1977: 8 1974: 7 6 days ≥ 100oF in 23 years

6. Des Moines, Iowa Airport Data 1983: 13 11 days in 2012 1988: 10 1977: 8 1974: 7 6 days ≥ 100oF in 23 years

9. Iowa State-Wide Average Data

10. Iowa State-Wide Average Data Totals above 40” 1 year 5 years

11. Iowa State-Wide Average Data 1990-2011 highly favorable precip for crops

12. Cedar Rapids, Iowa Data

13. Cedar Rapids, Iowa Data 28.0” 39.0” 39% increase

14. Cedar Rapids, Iowa Data Years with more than 40 inches 18 2

15. “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.

16. Cedar Rapids, Iowa Data

17. Cedar Rapids, Iowa Data Creates runoff

18. Cedar Rapids, Iowa Data 69% increase 3.6days 6.1 days

19. Cedar Rapids, Iowa Data Number of Years with More than 8 Occurrences 0 9

21. Amplification of the Seasonality of Precipitation Spring Fall Winter Summer

22. Amplification of the Seasonality of Precipitation Spring Fall 21.2 => 25.3 inches (22% increase) 12.1 => 10.5 inches (13% decrease) Winter Summer

23. Precip Normal Normal 2012 1988 • 2012 1988 Accum deficit 2012 1988 1988 Stress 2012 1988 was Hotter in August Accum stress Normal Normal

24. Precip Normal Normal 2012 12 inches (30 cm) below normal going into 2013 1988 • 2012 1988 2012 1988 1988 Stress 2012 1988 was Hotter in August Accum stress Normal Normal

25. Mean Summer (JJA) Dew-Point Temperatures for Des Moines, IA Rise of 3oF in 42 years 12% rise in water content in 42 years

26. Iowa Statewide Summer Minimum Daily Temperature Illinois Decline of Length of Grain-Fill Period with Increasing Minimum Daily Temperature Illinois Yield Decline with Increasing Minimum Daily Temperature during Grain-Fill Period

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

28. 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)

29. 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)

30. 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

32. 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

33. So what about droughts in the future?

34. Iowa State-Wide Average Data Totals above 40” 1 year 5 years

35. Iowa State-Wide Average Data Totals above 40” 1 year 5 years 3 years 7 years 2012 Totals below 25”

36. Projected Future Variability in Growing Season Precipitation for Iowa More extreme high precip years More extreme low precip years CJ Anderson, ISU

37. Future Variability in Growing Season Precipitation for Iowa More extreme high precip years Lines drawn by eye More extreme low precip years CJ Anderson, ISU

38. 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

39. For More Information: • Climate Science Program • Iowa 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