1. Image courtesy of NASA/GSFC

2. Global Climate Change: What About Agriculture?
Eugene S. Takle
Director, Climate Science Initiative
Professor of Atmospheric Science
Department of Geological and Atmospheric Sciences
Professor of Agricultural Meteorology
Department of Agronomy
Iowa State University
Ames, Iowa 50011
iPlant Collaborative
Biosphere II
27 September 2008

3. Source: IPCC, 2001: Climate Change 2001: The Scientific Basis

4. Source: IPCC, 2001: Climate Change 2001: The Scientific Basis

6. Source: Jerry Meehl, National Center for Atmospheric Research
From Jerry Meehl
This slide shows the time evolution of globally averaged surface air
temperature from multiple ensemble simulations of 20th century climate
from the NCAR Parallel Climate Model (PCM) compared to observations.
The simulations start in the late 19th century, and continue to the year
The temperature scale at left is in degrees Centigrade, and
temperature anomalies are calculated relative to a reference period
averaged from 1890 to The black line shows the observed data, or
the actual, recorded
globally averaged surface air temperatures from the past century. The
blue and red lines are the average of four simulations each from the
computer model. The pink and light blue shaded areas depict the range
of the four simulations for each experiment, giving an idea of the
uncertainty of a given realization of 20th century climate from the
climate model. The blue line shows the average from the four member
ensemble of the simulated time evolution of globally average surface air
temperature when only "natural" influences (solar variability and
volcanic eruptions) are included in the model. Therefore, the blue
line represents what the model says global average temperatures would
have been if there had been no human influences. The red line shows the
average of the four member ensemble experiment when natural forcings AND
anthropogenic influences (greenhouse gases including carbon dioxide,
sulfate aerosols from air pollution, and ozone changes) are included in
the model. Note that this model can reproduce the actual, observed data
very well only if the combined effects of natural and anthropogenic
factors are included. The conclusion that can be drawn is that
naturally occuring influences on climate contributed to most of the
warming that occurred before WWII, but that the large observed
temperature increases since the 1970s can only be simulated in the model
if anthropogenic factors are included.
This confirms the conclusion of the IPCC Third Assessment Report that
most of the warming we have observed in the latter part of the 20th
century has been due to human influences.
Source: Jerry Meehl, National Center for Atmospheric Research

7. IPCC Fourth Assessment Report Summary for Policy Makers

8. Energy intensive Energy conserving Mitigation Possible Adaptation
Reduced Consumption
Energy conserving
Possible
Mitigation
Necessary
Adaptation
IPCC Fourth Assessment Report Summary for Policy Makers

11. Projected changes in precipitation between and for an energy-conserving scenario of greenhouse gas emissions
IPCC 2007

12. Precipitation minus Evaporation for Western US
(25N-40N, 95W-125 W)
R. Seager, et al.,2007. Model Projections of an Imminent Transition to a More Arid Climate in Southwestern North America. Science, Vol no. 5828, pp

13. Projected Changes* for the Climate of the Midwest Temperature
Longer frost-free period (high)
Higher average winter temperatures (high)
Fewer extreme cold temperatures in winter (high)
Fewer extreme high temperatures in summer in short term but more in long term (medium)
Higher nighttime temperatures both summer and winter (high)
More freeze-thaw cycles (high)
Increased temperature variability (high)
*Estimated from IPCC reports
Follows trend of last 25 years and projected by models
No current trend but model suggestion or current trend but model inconclusive
*Estimated from IPCC reports

14. Projected Changes* for the Climate of the Midwest Precipitation
More (~10%) precipitation annually (medium)
Change in “seasonality”: Most of the increase will come in the first half of the year (wetter springs, drier summers) (high)
More water-logging of soils (medium)
More variability of summer precipitation (high)
More intense rain events and hence more runoff (high)
Higher episodic streamflow (medium)
Longer periods without rain (medium)
Higher absolute humidity (high)
Stronger storm systems (medium)
More winter soil moisture recharge (medium)
Snowfall increases (late winter) in short term but decreases in the long run (medium)
*Estimated from IPCC reports
Follows trend of last 25 years and projected by models
No current trend but model suggestion or current trend but model inconclusive

15. Projected Changes* for the Climate of the Midwest Other
Reduced wind speeds (high)
Reduced solar radiation (medium)
Increased tropospheric ozone (high)
Accelerated loss of soil carbon (high)
Phenological stages are shortened high)
Weeds grow more rapidly under elevated atmospheric CO2 (high)
Weeds migrate northward and are less sensitive to herbicides (high)
Plants have increased water used efficiency (high)
*Estimated from IPCC and CCSP reports
Follows trend of last 25 years and projected by models
No current trend but model suggestion or current trend but model inconclusive

16. Suitability Index for Rainfed Agriculture
IPCC 2007

17. Suitability Index for Rainfed Agriculture
IPCC 2007

18. Projected changes in precipitation between and for an energy-conserving scenario of greenhouse gas emissions
IPCC 2007

19. US Corn Yields (Bushels/Acre)

21. Grain and oilseed consumption
has exceeded production 7 of last 8 years
Tostle, Ronald, 2008: Global Agricultural Supply and Demand: Factors Contributing to the Recent
Increase in Food Commodity Prices WRS-0801 May USDA/ERS

26. Lingering Questions Relating to Food Production and Climate Change
What regions now suitable for rainfed agriculture will become marginally suitable or unsuitable due to climate change?
What regions now unsuitable for rainfed agriculture might become suitable?

27. Lingering Questions Relating to Food Production and Climate Change
By how much will technological advances reduce the impact of climate change on agriculture?
Continued advances in drought tolerance for corn
Drought or excess-water tolerance for all crops
Availability (e.g., water), sustainability and political acceptance of expanded irrigation for agriculture
What dietary changes will occur that will impact demand?
Relative amount of meat in diets?
New crops?
More locally produced food?

28. Summary
Global temperature change of the last 30 years cannot be explained on the basis of natural radiative forcing alone. Only when anthropogenic effects are considered can we explain recent temperature trends
Mitigation efforts, although urgently needed, will have little effect on global warming until the latter half of the 21st century
Adaptation strategies should be developed for the next 50 years
Impact of climate change on global food production is yet to be evaluated with the most recent generation of global climate models