The economic effect of climate change on the U.S. farm sector and consumers depends on:
- Climate Change effects on global agricultural production.
- Geographic pattern of temperature and precipitation changes.
- Regional and local rates of climate change.
- How changes around the world affect export supplies and import demands in other global regions and the United States.
A number of approaches have been used to estimate the impact of climate change on agriculture. One important approach addresses the question: What will agriculture be like in a given changed climate? It assumes future values for climate parameters for assessments. The climate scenario is generally derived from computer-executed Global Climate Models (GCMs) with specified forcing mechanisms (e.g. double CO2 levels). Another approach is based on "thresholds" and attempts to define the limits of an agricultural system to tolerate changes in climate. This approach asks: What type, magnitude, and rate of change would significantly effect the existing agricultural system?
The conclusions from the various studies and approaches, using a range of methodologies, can be summarized as follows:
- Initial assumptions are critically important-garbage in, garbage out (GIGO) is an ongoing concern.
- Agriculture (crops and livestock) is clearly sensitive to climate change in both positive and negative ways.
- Climate change will most likely bring regional shifts in production and increased demand for irrigation; if extreme weather events were to become more frequent, the outlook for agriculture could become much less favorable.
- Projected impacts depend strongly on the severity of the climate change scenarios, as well as possible changes in climate variability.
- Studies tend to show worsening effects as the various temperatures approach the high end of the projected range for a 2x CO2 climate scenario.
- Initial estimates of negative impacts of climate change on agriculture are likely to be overestimated without more consideration of:
- Economic adjustments and the broader economic and environmental implications of such changes;
- Greater sectorial flexibility and adaptation potential indicated in research results;
- CO2 fertilization effects.
- When such factors are considered, impacts on U.S. agriculture may be small, perhaps slightly negative or slightly positive (at least for a doubling of CO2).
- But regional impacts may be significant (with some regions gaining and some losing).
- Better climate change forecasts are key to improved assessments of the impacts of climate change on agriculture.
- Agriculture is a sector that can adapt to climate change, but many factors that have not been included in the assessments that could drastically change the above-rather benign-conclusions.