1. Past and Projected Changes in Continental-Scale Agro-Climate Indices Adam Terando NC Cooperative Research Unit North Carolina State University 2009 NPN RCN Meeting

2. Motivating Questions Is the late 20 th century warming found in the surface temperature record also observable in alternative climate measures that are critical to agricultural production and phenological observations in North America? Do Global Climate Models (GCMs) have skill in hindcasting the observed trends? What changes do GCMs predict for the future?

3. National Climatic Data Center: 2006 Global Mean Temperature over Land & Ocean Global Scale

4. BUT….. An increase in mean global surface temperature will not necessarily be reflected in the same manner for other manifestations of the climate system over the same time period and at different spatial scales.

5. Meehl et al. 2000

6. A Temperature Example Heat Stress Frost/Freeze Crop Growth

7. Agro-Climate Indices Annual Frost Days (t min < 0 o C) Growing Degree Days (thermal time) for Corn (10 < t avg < 30 o C) –Strong correlation with crop growth Heat-Stress Index (t max > 30 o C)

8. US and Canadian Long-term Historical Climate Networks

9. 1900 1880 1920 1940 1960 1980 2000 -0.6-0.4-0.20.00.20.40.6 1956 2005 1956 1975 1976 2000 1976 2005 1956 2005 Trend Time Periods 1956 – 2005: Good data coverage Switch in 1970s Warming signal detected then on global scale. Also coincides with phase shift in North American tele- connections (i.e. PDO, NAO) Most recent data

10. SPATIAL PATTERNS

11. Frost Trends (1956 – 2005) Slope (Days/Year) < -0.5 > 0.5 1 0

12. Growing Degree Day Trends (1956 – 2005) Slope (Days/Year) > 5 < -5 7 -7 0

13. Heat Stress Index Trends (1956 – 2005) (Degree Days Per Year) Slope > 2.5 < -2.5 10 -10 0

14. Percent Stations with Significant Trends

16. Trends fairly consistent through time a) b) c)

17. GCM Results

18. GCM Data 17 GCMs available from Lawrence Livermore National Laboratory Models used in IPCC AR4 Fewer years and model runs available for daily data than for monthly data (requires more storage!) Typically 40 years available for 20 th century (1961 – 2000), and two 20 years periods for 21 st Century (2045 – 2065 and 2081 – 2100)

19. Questions Do GCMs have skill in simulating past changes in agro-climate indices? What future changes do GCMs predict? Is the (projected) signal strong with respect to the model noise?

20. Evaluating GCM Skill

21. Poor performance for GDD and HSI evident in trend lines Good agreement with frost days r = 0.52 SLP obs = -0.22 SLP gcm = -0.21 r = 0.17 SLP obs = 0.50 SLP gcm = 3.42 r = 0.03 SLP obs = 0.04 SLP gcm = 1.59 GCM Arithmetic Mean Observations GCM Results Frost Days HSI GDD

23. Taylor Diagram Taylor 2001 Observation or ‘Perfect’ Model Correlation Coefficient RMS Error Model Result Standard Deviation

24. “perfect” model GCMs Schneider et al. 2007 Model Weighting

25. Frost Days Correlation Coefficient Standard Deviation Centered RMS Difference Thermal Time Correlation Coefficient Standard Deviation Centered RMS Difference Heat Stress Index

26. Correlation Coefficient Standard Deviation Centered RMS Difference Correlation Coefficient Standard Deviation Centered RMS Difference 16 Year Heat Stress Index Year Heat Stress Days a) b) c) d)

27. Negative Standard Deviations Positive Standard Deviations Minimum Temperature Maximum Temperature Correlation

28. bccr-bcm2.0 echam5-MPI miroc3.2 mri-cgcm2.3.2 observations

29. Projections

30. A2 Scenario IPCC Emission Scenarios

31. Frost Days Thermal Time Heat Stress Index GCM Arithmetic Mean 2046-2065 Weighted Mean 2081-2100 Weighted Mean Observations GCM Results

32. Projected changes large relative to model errors for 20 th century Largest uncertainties (model spread) around HSI projections

33. Conclusions General signal agreement between T avg and agro-climate indices. Strong increase in Thermal Time and decrease in Frost Days that is not seen in HSI. Still difficult for GCMs to model variables requiring high temporal resolution. Ensemble mean has greater skill than indiviudal GCMs Large changes in agro-climate indices predicted by GCMs for A2 scenario.