Preliminary Results California Max. and Min. Temperature Trends from Northern and Southern California Max. and Min. Temperature Trends from From Table 1., CAL, N-CAL, S-CAL Tmin trends during are positive and statistically significant at the ≥ 95% confident level. For statistically significant trends  N-CAL > S-CAL > CAL > NH > Global for Tmin. From Table 2., CAL, N-CAL, S-CAL Seasonal Tmin trends are positive and statistically significant at the ≥95% confident level except DJF in S-CAL. For CA climate regions, all regions annual Tmin are positive and statistically significant at the ≥ 95% confident level except North Coast and South Interior region. In similarity, all seasonal Tmin are positive statistically significant at the ≥ 95% confident level except North Coast, North Central, South Interior regions. For statistically significant trends in different regions  South Coast is the warmest 0.67 °F/decade for Annual Tmin  Mohave is the warmest 0.76 °F/decade for DJF Tmin  South Coast is the warmest 0.78 °F/decade for MAM Tmin  Mohave is the warmest 0.73 °F/decade for JJA Tmin  South Coast is the warmest 0.61 °F/decade for SON Tmin  Sacramento-Delta is the warmest 0.35 °F/decade for DJF Tmax  North Coast is the warmest 0.46 and 0.47 °F/decade for MAM and JJA Tmax respectively. California Surface Temperature Trends W. Kessomkiat 1, E. Cordero 1, and L. Bereket 2 1 Department of Meteorology, San José State University, San José, CA, USA; 2 Department of Mechanical Engineering, Santa Clara University, Santa Clara, CA, USA Summary Statistically significant warming trends (95% confidence level) are observed over California in different climate regions.  Annual Tmin Trends for CAL, N-CAL, S-CAL from °F/decade.  Seasonal Tmin Trends for all climate regions from °F/decade  California minimum temperatures are rising faster than maximum temperatures similar to global observations.  Coastal regions are significantly warming faster than In-land regions as shown in North Coast JJA Tmax 0.47 °F/decade and in South Coast MAM Tmin 0.78 °F/decade. Future Plans  Perform additional data quality analysis  Use output from climate models simulation to investigate role of anthropogenic forcing on CA temperature trends Acknowledgments. This work was supported in part NSF’s Faculty Early Career Development (CAREER) Program, Grant ATM and NASA’s Living with a Star, Targeted Research and Technology Program, Grant LWS Introduction Over decades, climate research has been conducted to determine whether the global temperature have increased as a result of the increase in anthropogenic greenhouse gases. The Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report has recently shown the global temperature has been increasing since mid-twentieth century and that this was very likely (90% confidence) due to the increase in anthropogenic greenhouse gases. Our research is to study and understand how California temperature variations and the connection with anthropogenic forcing. Data and Methodologies  The California temperature data is obtained from NCDC. (National Weather Service Cooperative Observers (Coop) stations)  Data quality control and methods use the following criterias - no months are used if more than 6 days are missing. - seasons are defined using the standard meteorological definition. (winter = DJF, spring = MAM, summer = JJA, and fall = SON) - no seasons are used if more than one month is missing. - no annual value is used if more than one month is missing.  All trends are computed via least squares regression.  Statistical significance is computed using standard error with auto correlation taken into account Fig. 2 CAL Max. and Min. Annual Temperature Fig. 1 Map of California Climate Weather Regions (DRI) as shown in Table 2. Fig. 3 N-CAL Max and Min Annual Temperature Fig. 4 S-CAL Max and Min Annual Temperature Table. 1. Trends (ºF per decade) From Different Time Periods for Maximum Annual Temperature, Minimum Annual Temperature for Global land areas, Northern Hemisphere, Northern and Southern California, (* shows statistically significant at ≥ 95% confident level) Annual Trends ( ° F per decade) Data Global Tmean1.33 (IPCC AR4) ( )0.30 (IPCC AR4) Global Tmax0.25 (Vose et al. 2005) ( )0.52 (Vose et al. 2005) Global Tmin0.37 (Vose et al. 2005) ( )0.53 (Vose et al. 2005) Northern Hemisphere Tmean0.14 (Lugina et al. 2006) ( )0.54 (Lugina et al. 2006) Northern Hemisphere Tmax0.30 (Vose et al. 2005) ( )0.61 (Vose et al. 2005) Northern Hemisphere Tmin0.41 (Vose et al. 2005) ( )0.65 (Vose et al. 2005) California Tmax California Tmin0.43*0.23 Northern California Tmax Northern California Tmin0.53*0.30 Southern California Tmax Southern California Tmin0.51*0.26 Table. 2. Annual and Seasonal Trends (ºF per decade) From for Maximum Temperature, Minimum Temperature for Different Regions in California (* shows statistically significant at ≥ 95% confident level) SeasonMaximumMinimumSeasonMaximumMinimum CaliforniaE. Sacramento-Delta Region Annual *Annual * DJF *DJF0.35*0.54* MAM *MAM * JJA *JJA * SON *SON * Northern CaliforniaF. Central Coast Region Annual *Annual * DJF *DJF * MAM *MAM0.37*0.56* JJA *JJA0.23*0.50* SON *SON * Southern CaliforniaG. San Joaquin Valley Region Annual *Annual * DJF DJF * MAM *MAM * JJA *JJA * SON *SON * A. North Coast RegionH. South Coast Region Annual0.29*0.05Annual * DJF DJF * MAM0.46*0.22MAM0.45*0.78* JJA0.47*0.17*JJA * SON SON * B. North Central RegionI. South Interior Region Annual *Annual DJF *DJF MAM *MAM * JJA *JJA * SON SON C. Northeast RegionJ. Mohave Region Annual *Annual0.20*0.62* DJF DJF * MAM *MAM * JJA *JJA0.33*0.73* SON SON * D. Sierra RegionK. Sonoran Region Annual *Annual * DJF *DJF * MAM *MAM0.43*0.60* JJA *JJA * SON *SON *