It is shown that the stationary fluctuations described by the diffusion equation of an effective space dimension less than one have a 1/fspectrum. A physical diffusion model equivalent to such a low dimensional diffusion process is proposed. Here, a singular disturbance of temperature fluctuation is assumed to diffuse with the space‐dependent diffusion coefficientD(r)=D0(1+&kgr;r−m)&thgr;. Here,D0is the constant part of the diffusion coefficient and &kgr;r−mrepresents the effect of local temperature enhancement of the background medium caused by the singular disturbance itself, whereris the distance from the singular disturbance atr=0, andmand &thgr; positive constants.