Climate Change and Agriculture Eugene S. Takle Professor of Agricultural Meteorology, Department of Agronomy Professor of Atmospheric Science, Department of Geological and Atmospheric Sciences Director, Climate Science Initiative Iowa State University gstakle@iastate.edu Agricultural Summit and Roundtable, Ames, IA 31 July 2008

Natural and anthropogenic contributions to global temperature change (Meehl et al., 2004). Observed values from Jones and Moberg 2001. Grey bands indicate 68% and 95% range derived from multiple simulations. Natural cycles

Natural and anthropogenic contributions to global temperature change (Meehl et al., 2004). Observed values from Jones and Moberg 2001. Grey bands indicate 68% and 95% range derived from multiple simulations. Not Natural

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 2000. The temperature scale at left is in degrees Centigrade, and temperature anomalies are calculated relative to a reference period averaged from 1890 to 1919. 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

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

Suitability Index for Rainfed Agriculture IPCC 2007

Suitability Index for Rainfed Agriculture IPCC 2007

Projected changes in precipitation between 1980-1999 and 2080-2099 for an energy-conserving scenario of greenhouse gas emissions IPCC 2007

Insured Crop Loss for Corn in Iowa*   Factor Percent Cold Winter 0.9 Decline in Price 6.6 Drought 35.5 Excess Moist/Precip/Rain 38.4 Flood 2.6 Freeze 0.1 Hail 7.2 Heat 1.2 Hot Wind 0.0 Mycotoxin (Aflatoxin) 1.0 Plant Disease 0.3 Winds/Excess Wind 5.0 Other 1.1 Total 100.0 *Milliman, Inc., based on 1995-2006 data from the Risk Management Agency Website (http://www.rma.usda.gov/)

Insured Crop Loss for Corn in Iowa*   Factor Percent Cold Winter 0.9 Decline in Price 6.6 Drought 35.5 Excess Moist/Precip/Rain 38.4 Flood 2.6 Freeze 0.1 Hail 7.2 Heat 1.2 Hot Wind 0.0 Mycotoxin (Aflatoxin) 1.0 Plant Disease 0.3 Winds/Excess Wind 5.0 Other 1.1 Total 100.0 *Milliman, Inc., based on 1995-2006 data from the Risk Management Agency Website (http://www.rma.usda.gov/)

Insured Crop Loss for Soybeans in Iowa* Factor Percent Cold Winter 0.6 Decline in Price 4.8 Drought 56.8 Excess Moist/Precip/Rain 20.2 Flood 1.4 Freeze 0.1 Hail 13.0 Heat 0.9 Hot Wind 0.0 Mycotoxin (Aflatoxin) 0.0 Plant Disease 1.1 Winds/Excess Wind 0.2 Other 1.1 Total 100.0 *Milliman, Inc., based on 1995-2006 data from the Risk Management Agency Website (http://www.rma.usda.gov/)

Insured Crop Loss for Soybeans in Iowa* Factor Percent Cold Winter 0.6 Decline in Price 4.8 Drought 56.8 Excess Moist/Precip/Rain 20.2 Flood 1.4 Freeze 0.1 Hail 13.0 Heat 0.9 Hot Wind 0.0 Mycotoxin (Aflatoxin) 0.0 Plant Disease 1.1 Winds/Excess Wind 0.2 Other 1.1 Total 100.0 *Milliman, Inc., based on 1995-2006 data from the Risk Management Agency Website (http://www.rma.usda.gov/)

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) Follows trend of last 25 years and projected by models No current trend but model suggestion or current trend but models inconclusive *Estimated from IPCC reports

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) Snowfall increases (late winter) in short term but decreases in long run (medium) More winter soil moisture recharge Follows trend of last 25 years and projected by models No current trend but model suggestion or current trend but models inconclusive *Estimated from IPCC reports

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 states 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) Follows trend of last 25 years and projected by models No current trend but model suggestion or current trend but models inconclusive *Estimated from IPCC and CCSP reports