Comments on “Methodology and Results of Calculating Central California Surface Temperature Trends: Evidence of Human-Induced Climate Change?”

• Published in: Journal of climate Vol. 20; no. 17; pp. 4486 - 4489
• Main Authors: Bonfils, Céline, Duffy, Philip B., Lobell, David B.
• Format: Journal Article
• Language: English
• Published: Boston American Meteorological Society 01.09.2007
• Subjects: Agricultural land; Asphalt; Carbon dioxide; Climate change; Climate models; Climatic zones; Climatology; Communication; Cooling; Datasets; Educational environment; Human influences; Hypotheses; Irrigation; Land use; Meteorology; Minimum temperatures; Mountains; Night; Night-time; Nighttime; NOTES AND CORRESPONDENCE; Personal communication; Population growth; Regions; Seasonal variations; Summer; Surface temperature; Temperature; Temperature effects; Temperature trends; Trends; Urban development; Urbanization; Valleys; San Joaquin Valley; California; Central Valley; United States > US; USA, California
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/JCLI4247.1

[...]strong positive trends in nighttime temperature are a common feature throughout the western United States (A. Hamlet 2006, personal communication). Regional model simulations, for example, show greater warming response to increased CO2 in the mountains than in the valley, even though these simulations do not represent irrigation or other forms of land use change (Duffy et al. 2006). [...]differences in mountain versus valley meteorology can result in different temperature trends. In the Central Valley, the population growth, the urban development (Bereket et al. 2005), and an increase in dirt and asphalt roads to access agricultural fields might also be at the origin of some increases in nighttime surface temperature. According to the observational datasets used here, the rise in minimum temperatures has occurred across the entire state (although it is not significant everywhere), affected all elevations (Fig. 1), and accelerated during the second half of the twentieth century, which suggests a large-scale influence on California climate.