Climate Variability and Adaptation
Implications for Farmers in the United States
Changes in Climate and Weather
Many scientists believe that the escalating release of greenhouse gas (GHG) emissions into the
atmosphere is raising temperatures and changing global climate patterns. These scientists include the
Intergovernmental Panel on Climate Change (IPCC), a panel of thousands of experts representing
member countries of the United Nations and the World Meteorological Organization.
The figures below represent one possible scenario for changes in temperature and precipitation under a
climate change model:i
It is widely accepted that climate variability could cause:
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Shifts in temperature and precipitation
An increase in extreme weather events, such as downpours or droughts
Changes in season length, timing and conditions
Some of the most pronounced effects of climate variability for agriculture in the United States are
predicted to be extreme events, such as heavy downpours and droughts.ii Precipitation in the US has
become less frequent but more intense, and this pattern is projected to continue.iii Drought frequency
and severity are also predicted to increase in the future over much of the United States.iv
These weather changes could have implications for agricultural production including:
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Changes in crop yield
Variations in plant tolerance
Changes in the water requirements of crops
Prevalence of crop disease, weeds, and pests
Effectiveness of herbicides and pesticides
Shifts in areas where food is produced
Another dynamic is that the availability of carbon dioxide in the atmosphere influences plant growth, an
effect known as CO2 fertilization. While CO2 fertilization promotes the growth of plants, it also has
implications for their chemical composition.v
The combination of these factors could have a positive or negative impact on farm productivity and
income depending on the crop and the region where it is produced. Overall, many crops in the United
States show positive responses to elevated CO2 and low levels of warming, but higher levels of warming
would have a negative effect on crop growth and yields.vi
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Corn
o
o
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A recent study by the International Food Policy Research Institute (IFPRI) estimates that
climate change could affect corn production in developed countries by decreasing
irrigated corn yield from -1.2% to -8.7%, while changing non-irrigated corn yield from
0.6% to -5.7%.vii
Analysis suggests that even moderate increases in temperature could decrease yields of
corn in the US.viii USDA projects that corn yields could decrease by 4.0% from higher
temperatures, or a net decrease of 3.0% if the effect of CO2 fertilization is taken into
account.ix
Cotton
o Analysis suggests that even moderate increases in temperature could decrease yields of
cotton in the US.x USDA projects that cotton yields in the South could decrease by 5.7%
from higher temperatures, but could increase 3.5% if the effect of CO2 fertilization is
taken into account.xi
o
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Rice
o
o
A recent NAS study examined the impact of climate change and temperature extremes
on crop yields, and estimated that cotton yields in the US could decrease by 20% in the
midterm to as much as 75% in the long-term depending on the degree of temperature
change.xii
Analysis suggests that even moderate increases in temperature could decrease yields of
rice in the US.xiii USDA projects that rice yields could decrease by 12.0% from higher
temperatures, or a net decrease of 5.6% if the effect of CO2 fertilization is taken into
account.xiv
A recent study by the International Food Policy Research Institute (IFPRI) estimates that
climate change could affect rice production in developed countries by decreasing
irrigated rice yield from 3.5% to 5.55%, while increasing non-irrigated rice yield from
10.3% to 17.3%.xv
While the full impacts of changes to greenhouse gas emissions and the climate continue to be
analyzed, changes in weather variability have clear risks for US farmers. There are a number of ways
to mitigate these risks including reducing and sequestering greenhouse gas emissions.
Adaptation
Summary
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Changes in weather variability are a risk for US farmers
Laura Sands
The Clark Group, LLC
Sara Hessenflow Harper
(202) 544-8200
Sara Brodnax
www.clarkgroupllc.com
REFERENCES
i
Climate simulation using the US National Center for Atmospheric Research model of the A25 scenario of the IPCC’s
Fourth Assessment Report. International Food Policy Research Institute. Oct 2009. Climate Change: Impact on
Agriculture and Costs of Adaptation. Online at http://www.ifpri.org/sites/default/files/publications/pr21.pdf.
ii
US Global Change Research Program. 2009. Climate Change Impacts by Sector: Agriculture. Online at
http://globalchange.gov/publications/reports/scientific-assessments/us-impacts/climate-change-impacts-bysector/agriculture.
iii
Ibid.
iv
Ibid.
US Global Change Research Program. 2009. Climate Change Impacts by Sector: Agriculture. Online at
http://globalchange.gov/publications/reports/scientific-assessments/us-impacts/climate-change-impacts-bysector/agriculture.
vi
Ibid.
vii
Percent change from yield with 2000 climate to yield with 2050 climate. International Food Policy Research
Institute. Op. cit.
viii
Ibid.
ix
US Climate Change Science Program and the Subcommittee on Global Change Research. Op. cit.
x
Ibid.
xi
US Climate Change Science Program and the Subcommittee on Global Change Research. 2008. The effects of
climate change on agriculture, land resources, water resources, and biodiversity in the United States. US
Department of Agriculture. Online at http://www.usda.gov/oce/global_change/files/CCSPFinalReport.pdf.
xii
Schlenker, W. and M. J. Roberts. 15 Sep 2009. Nonlinear temperature effects indicate severe damages to U.S.
crop yields under climate change. Proc. Natl. Acad. Sci. 106(37):15594-8.
xiii
Ibid.
xiv
US Climate Change Science Program and the Subcommittee on Global Change Research. 2008. The effects of
climate change on agriculture, land resources, water resources, and biodiversity in the United States. US
Department of Agriculture. Online at http://www.usda.gov/oce/global_change/files/CCSPFinalReport.pdf.
xv
Percent change from yield with 2000 climate to yield with 2050 climate. International Food Policy Research
Institute. Oct 2009. Climate Change: Impact on Agriculture and Costs of Adaptation. Online at
http://www.ifpri.org/sites/default/files/publications/pr21.pdf.
v