1. Accumulated Winter Chill is Decreasing in Fruit Growing Regions of California Dennis Baldocchi University of California, Berkeley Ag and Food Board Modesto, CA November 29, 2012

2. ESPM 111 Ecosystem Ecology

3. Berkeley Earth Temperature Project Re-Confirms Global Warming http://berkeleyearth.org/

4. ESPM 111 Ecosystem Ecology

5. What is Happening in the Central Valley?

6. Mean Annual Air Temperature at Modesto is Warming

7. Impacts of Warmer Temperature on Agriculture? More Evaporation and Water Use Earlier Growing Season – Faster phenology – Risk of frost – Asynchrony between flowering and pollinators Less Winter Chill and Dormancy – Reductions in Yield

8. Distribution of Orchards Luedeling et al 2009 PLOS

9. Deciduous Fruit Trees Need Dormancy and Rest during the Winter

10. Estimating Winter Chill

11. Map of Chill-Degree Hours

12. Downward Trend in Chill Hours near Brentwood, East Contra Costa 20 year record, CIMIS Data

13. Downward Trend in Chill Hours near Orland, northern Sac Valley 50+ year Record, Coop Data

14. Trends in Chill Hours

15. Trends in Chill Degree hours

16. Potential Trends, based on Climate Scenarios

17. Winter Chill Models Darbyshire et al 2011. AgForMet

18. Luedeling et al 2009 PLOS Safe Chill, 10 th Quintile of the Chill Probability Distribution, A Conservative Measure of Potential Chill

19. Reductions in Winter Chill are Predicted, but Less Severe with Dynamic Model

20. Luedeling et al 2009 PLOS Map with Classic Chill Model

21. Map with Dynamic Model

22. Proposed Hypotheses as to Why Winter Chill Accumulation is Declining Are Downward Trends in Winter Tule Fog Occurring? Are they amplifying effects of global warming, by causing a switch in the surface energy balance?

23. Detecting Trends in Fog Remote Sensing, AVHRR and MODIS – Time Series extends back to 1981 – Gives good spatial coverage – Two samples per day; does not detect night fog – Can’t see through Clouds Automated Weather Stations, CIMIS – Time series extends back to 1982 – Poor spatial Coverage Coop Weather Stations – Time Series extends back to 1920s – Few Stations – Fog must be inferred from rain and temperature

24. Central Valley Tule Fog, Iconic Case

25. Clear Fog Fog and Clouds Clouds and Fog Science and Art in Detecting Fog and Fog Area

26. Presence and Absence of Fog has Marked Influence on Temperature and Solar Radiation

27. mm d -1 MJ m -2 d -1oCoC oCoC oCoC pptRgRg T ave T max T min RHT dew Brentwood0.103.777.3810.274.3492.306.23 Davis0.304.186.429.783.5391.775.13 Firebaugh0.093.637.6310.204.8595.326.92 Five Points0.543.445.398.974.0593.274.39 Gerber0.265.747.6913.153.5185.085.20 Kettleman City0.274.678.2111.225.3786.866.06 Modesto0.133.767.049.904.1392.935.95 Parlier0.143.787.7110.575.3093.256.67 Twitchell Island0.193.454.757.682.1594.553.92 Westlands0.093.597.6110.214.9091.706.40 ave0.214.006.9810.194.2191.705.69 std0.140.711.121.410.983.250.99 Weather under Tule Fog

28. MJ m -2 d -1 RgRg T ave T max T min RH Brentwood11.529.5517.122.5360.43 Davis11.288.8816.802.0558.74 Firebaugh11.228.6517.370.8963.37 Five Points12.358.3317.560.6461.22 Gerber Kettleman City11.9210.2217.892.6756.89 Modesto11.267.4716.89-0.1870.03 Parlier11.538.5117.621.3371.03 Twitchell Island11.778.7417.071.2666.90 Westlands12.048.1217.84-0.3659.89 mean11.658.7217.351.2063.17 stddev0.390.800.401.095.05 Weather Clear Days during the Fog Season

29. Temperature Difference, Bud-Air

30. Weather Conditions on Fog Days

31. Weather Conditions on Clear Days, during Fog Season

32. Fraction of Fog, AVHRR 1981-1999

33. Downward Trend in the Fraction of Fog Days-Area in the Central Valley

36. Conclusions Downward Trends in Winter Chill are Being computed with the Simple Classical Model and the Better Dynamic Model Downward Trends in Winter Fog are Occurring Trends in Fog are Contributing to Downward Trend in Winter Chill More Clear and Warm Days will have a Negative Effect on Accumulated Winter Chill, Amplifying Reductions in Winter Chill Fog is not Explicitly Modeled in the Climate Scenarios Used so Far