The Earth's temperature is rising as a result of increased atmospheric concentrations of greenhouse gases (see Basic Information on Climate Change from U.S. Environmental Protection Agency). If greenhouse gas (GHG) emissions continue increasing at a high rate (essentially business-as-usual), climate models predict that global warming could increase 4.7-8.6º F above 1986–2005 levels by the end of this century (Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report Vol. I, Summary for Policy Makers). While alternative scenarios with lower rates of increase in atmospheric greenhouse gases and temperatures exist, they all call for more frequent and lengthy heat waves in the future. As the Earth warms, currently wet regions are expected to receive more rainfall, and currently dry regions receive less, although there will be exceptions and there is considerable uncertainty on how and how much climate change will affect specific locations.
Human activities across the globe—including fossil fuel use, deforestation, and agricultural practices—are contributing to the buildup of atmospheric carbon dioxide and other greenhouse gases. Since 1750, land-use change has been responsible for roughly 32 percent of human emissions of carbon dioxide (IPCC Fifth Assessment Report, Vol. I).
Within the United States, agriculture and forestry together accounted for 9.1 percent of U.S. greenhouse gas emissions in 2014. If electricity sector emissions are allocated to the sectors using electricity, agriculture and forestry’s share of GHG emissions increases to 10.0 percent.
The greenhouse gas profile of the agricultural and forestry sector differs substantially from the profile of other sectors. Agriculture is an emissions-intensive sector; it accounted for less than 1 percent of U.S. production (in real gross value-added terms), but emitted 10 percent of U.S. GHGs in 2014. Energy-related CO2 emission sources—which dominate GHG emissions in most other production sectors—are dwarfed in agriculture by unique crop and livestock emissions of nitrous oxide and methane. Crop and pasture soil management generates the most GHG emissions, due largely to the use of nitrogen-based fertilizers and other nutrients. Enteric fermentation (digestion in ruminant livestock) and manure management ranks second. Agriculture and forestry are unique in providing opportunities for withdrawing carbon from the atmosphere through biological sequestration in soil and biomass carbon sinks. The carbon sinks, which are largely due to land use change from agricultural to forest land (afforestation) and forest management on continuing forest, offset 11.5 percent of total U.S. GHG emissions in 2014 (see Agricultural Production and Mitigation).
The National Climate Assessment
The U.S. Global Change Research Program (USGCRP) aims "to assist the Nation and the world to understand, assess, predict, and respond to human-induced and natural processes of global change." In this role, every four years it produces a National Climate Assessment (NCA) that surveys and synthesizes the most recent science about climate change impacts and adaptation in the United States. ERS participated in the development of the most recent NCA, released in May 2014 (see the 2014 National Climate Assessment). The 2014 study reported that global warming observed over the past 50 years is primarily due to human activities. The agriculture chapter concludes that disruptions to agricultural production due to climate change have been increasing and are projected to become more severe over the foreseeable future. After 2050, the negative impacts on agriculture of increased climate-induced stress are projected to increase, due to the incidence of weeds, diseases, and insect pests, affecting productivity of most crops and livestock in addition to weather-related stresses. (See more highlights of the agriculture chapter of the 2014 NCA).
ERS conducts research on a range of climate change issues, including:
- The impacts of climate change on crop and livestock production
- The implications of climate change for food security
- The international land use implications of bioenergy and food production
- The potential for agriculture to adapt to changing climate conditions.
- The potential within agriculture for mitigation of GHG emissions
- The role of USDA farm programs under changing climate conditions
- The value of data and decision-making tools under changing climate conditions.