Top: power spectra the periodic systematic effect before (red curve) and after removal. Green: destriping only. Filtering without baseline removal – cyan: filtering only, yellow: filtering + destriping. Filtering with baseline removal – blue: filtering only, orange: filtering + destriping. Note that the yellow, orange, and blue curves are superimposed, meaning that the three cases produced the same results. Bottom: impact of periodic fluctuations on large scales compared to the CMB and cosmic variance obtained from a best-fit solution of the seven year WMAP data.