Land-use and land-cover changes affect local, regional, and global climate processes.

This finding is from chapter 13 of Climate Change Impacts in the United States: The Third National Climate Assessment.

Process for developing key messages: The author team benefited from a number of relevant technical input reports. One report described the findings of a three-day workshop held from November 29 to December 1, 2011 in Salt Lake City, in which a number of the chapter authors participated.94a7e73a-f733-42d4-be5a-5bd6d861a6e4 Findings of the workshop provided a review of current issues and topics as well as the availability and quality of relevant data. In addition, from December 2011 through June 2012 the author team held biweekly teleconferences. Key messages were identified during this period and discussed in two phases, associated with major chapter drafts. An early draft identified a number of issues and key messages. Based on discussions with National Climate Assessment (NCA) leadership and other chapter authors, the Land Use and Land Cover Change authors identified and reached consensus on a final set of four key messages and organized most of the chapter to directly address these messages. The authors selected key messages based on the consequences and likelihood of impacts, the implied vulnerability, and available evidence. Relevance to decision support, mitigation, and adaptation was also an important criterion for the selection of key messages for the cross-cutting and foundational topic of this chapter.

Description of evidence base: The dependence of weather and climate processes on land surface properties is reasonably well understood in terms of the biophysical processes involved. Most climate models represent land-surface conditions and processes, though only recently have they begun to incorporate these conditions dynamically to represent changes in the land surface within a model run. Regional weather models are increasingly incorporating land surface characteristics. Extensive literature – as well as textbooks – documents this understanding, as do models of land surface processes and properties. A Technical Input report to the National Climate Assessment74461848-086f-4ea7-b3b3-e1693e3a21d8 summarizes the literature and basic understanding of interactions between the atmosphere and land surface that influence climate. Examples are provided within the chapter to demonstrate that land-use and land-cover change are affecting U.S. climate.062cab4d-e6a4-458a-8941-9485c1e9cdfb 20a2fadd-ce98-440a-8245-35eef796dce8 3449fa91-2545-4625-b3f8-8a15f1e354ee 5fd4934a-2c98-4b94-8179-ff4536a243bf 71fd8e9a-5d84-4d79-bff0-35da4ee4e999 ff31c479-bfb9-4c80-8ea1-9486048e1abb 0e3dedb6-cea3-4d09-9c9c-74ab9bb83623 c33568be-8745-48f0-8d1f-9178d4618c0a 57b390b7-6a1b-42e0-8228-6dce780c4b99 fd18b4db-8742-4fe9-b588-4f8b5d3cb353 7591e0ad-a4cf-43cb-986f-8cc2d5d35b70

New information and remaining uncertainties: While there is little uncertainty about this key message in general, the heterogeneity of the U.S. landscape and associated processes, as well as regional and local variations in atmospheric processes, make it difficult to analyze or predict the character of land use and land cover influences on atmospheric processes at all scales.

Assessment of confidence based on evidence: Very High. The basic processes underlying the biophysics of interactions between the land surface and atmosphere are well understood. A number of examples and field studies are consistent in demonstrating effects of land use and land-cover change on the climate of the U.S.

References :

• National Climate Assessment Technical Report on the Impacts of Climate and Land Use and Land Cover Change (74461848)
• Temperature and equivalent temperature over the United States (1979-2005) (062cab4d)
• Late 20th century land change in the Central California Valley Ecoregion (20a2fadd)
• Observational Evidence for Reduction of Daily Maximum Temperature by Croplands in the Midwest United States (3449fa91)
• How significant is the impact of irrigation on the local hydroclimate in California’s Central Valley? Comparison of model results with ground and remote-sensing data (5fd4934a)
• Two decades of urban climate research: a review of turbulence, exchanges of energy and water, and the urban heat island (71fd8e9a)
• Man-Made Climatic Changes: Man's activities have altered the climate of urbanized areas and may affect global climate in the future (ff31c479)
• Rainfall Modification by Major Urban Areas: Observations from Spaceborne Rain Radar on the TRMM Satellite (0e3dedb6)
• Applied climatology: urban climate (c33568be)
• Urban Heat Islands: Observations, Impacts, and Adaptation (57b390b7)
• Urban Modification of Thunderstorms: An Observational Storm Climatology and Model Case Study for the Indianapolis Urban Region (fd18b4db)
• Baseline and Projected Future Carbon Storage and Greenhouse-Gas Fluxes in the Great Plains Region of the United States. Professional Paper 1787 (7591e0ad)
• Land Use and Land Cover National Stakeholder Workshop Technical Report. Report prepared for 2013 National Climate Assessment (94a7e73a)