This to a property of the tiny CCD that consumer DSCs used.
No way to overcome it.
Since noise level (the S.D. value) doubles for every 7 degree C or so (differs betw CCD), the ways to minimise the noise is to reduce the temp of your DSC
1. take your picture ASAP after switching on your DSC, B4 it gets heated up.
2. never use the preview function of the LCD. This mode require the CCD to be active at all time and togather with the LCD backlite and the image processing chips produce a lot of heat (that's why your battery gets used up faster in LCD preview mode). Use the optical viewfinder instead.
Do not bother to cool your DSC to below room temp as this will cause condensation and water is bad...