Feb 15, 2016

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

John R. Christy and William B. Norris
AMS Journal of Climate


  • Describes a procedure to construct time series of regional surface temperatures and applies this to interior central California stations to test the hypothesis that century-scale trend differences between irrigated and nonirrigated regions may be identified
  • Generates time series of daily maximum and minimum temperatures for stations in the irrigated San Joaquin Valley (Valley) and for nearby nonirrigated Sierra Nevada (Sierra) for 1910–2003
  • Results show that twentieth-century Valley minimum temperatures are warming at a highly significant rate in all seasons, being greatest in summer and fall (> +0.25°C decade−1)
  • Finds the Valley trend of annual mean temperatures is +0.07° ± 0.07°C decade−1