Note: This data set has now been superseded by a new data set on the effects of climate change on global food production under SRES emissions and socio-economic scenarios produced by the same authors. Users are recommended to use the new data instead. SEDAC is maintaining this web site for reference purposes.
To better interpret the data sets developed by crop modeling studies,
users need to be aware of the many uncertainties that could not be addressed.
For more on these and other factors that cannot fully be taken into account
in crop-climate modeling, see the recent report entitled Climate
Change and U.S. Agriculture: The Impacts of Warming and Extreme Weather
Events on Productivity, Plant Diseases, and Pests by Rosenzweig, et
- Pests and diseases. The potential effects of climate change
on crop damage due to pests and diseases was not considered in the study
and assumed to remain at the current level. At present damage is estimated
to reduce potential global crop yields by 30% each year. Future changes
in temperature and precipitation will undoubtedly effect the prevalence
and geographic extent of specific pests such as bacteria, nematodes,
and insects, which in turn will impact upon crop losses. Unfortunately,
these impacts could not be measured in this study.
- Climatic variability. Increased seasonal or annual climatic
variability as well as variability across small geographic areas is
expected to go hand-in-hand with broader secular trends in temperature
increase. These seasonal, annual and geographic variations are not captured
very well by existing GCMs, and therefore were not accounted for in
this study. For more on this topic, see studies on climate variability
in the Southeast
- Extreme weather events. Climate change is predicted to affect
the frequency and severity of extreme weather events such as cyclones,
hurricanes, and prolonged droughts. Extreme weather events can result
in significant crop losses from wind damage, flooding, or inadequate
soil moisture. Although it is recognized that extreme weather will affect
future yields, it is very difficult to model such stochastic events
in a way that provides realistic assessment of their yield impacts.
- Impacts of CO2 enrichment.
Thus far, the applications of enhanced concentrations of CO2
to crops have been conducted in highly controlled laboratory experiments.
The only exception to this is a major field-based set of experiments
in Arizona called the FACE
experiments. In all cases the crop growing conditions differ from
those in the real world, most notably in the control of weed competitors.
Under normal conditions, crops compete with weeds, which also respond
to climate change and enriched CO2
. Depending on the circumstances, the effect of climate change may be
for weeds to grow faster than field crops. This would have a negative
impact on crop yields, and would in all likelihood require greater application
of herbicides, a high-cost input.