Table 1.

Climate least-squares linear trends (in °C·decade⁻¹) in heavily irrigated areas of the Central Valley (CIF > 50%) relative to the modestly irrigated reference region (CIF between 0.1% and 10%)

Data set	Tmax 1915–1979	Tmin 1915–1979	Tave 1915–1979	DTR 1915–1979	Tmax 1980–2000
UW	−0.136 ± 0.051***	+0.022 ± 0.037	−0.057 ± 0.036***	−0.157 ± 0.053***	0.099 ± 0.150
PRISM	−0.165 ± 0.032***	+0.037 ± 0.032**	−0.064 ± 0.021***	−0.202 ± 0.047***	−0.052 ± 0.112
CRU2.1	−0.157 ± 0.065***	+0.018 ± 0.059	−0.070 ± 0.055**	−0.176 ± 0.059***	0.409 ± 0.294**
CRU2.0	−0.249 ± 0.099***	−0.122 ± 0.079***	−0.186 ± 0.084***	−0.128 ± 0.066***	0.297 ± 0.227**

The 2σ trend confidence intervals are adjusted for temporal autocorrelation effects (see http://www.pnas.org/cgi/content/full/0700144104/DC1SI Text).

**, P < 0.05;

***, P < 0.01.