  We explicate the origin of the temperature quadrupole in the adiabatic dark
energy model and explore the mechanism by which scale invariant isocurvature
dark energy perturbations can lead to its sharp suppression. The model requires
anticorrelated curvature and isocurvature fluctuations and is favored by the
WMAP data at about the 95% confidence level in a flat scale invariant model. In
an inflationary context, the anticorrelation may be established if the
curvature fluctuations originate from a variable decay rate of the inflaton;
such models however tend to overpredict gravitational waves. This isocurvature
model can in the future be distinguished from alternatives involving a
reduction in large scale power or modifications to the sound speed of the dark
energy through the polarization and its cross correlation with the temperature.
The isocurvature model retains the same polarization fluctuations as its
adiabatic counterpart but reduces the correlated temperature fluctuations. We
present a pedagogical discussion of dark energy fluctuations in a quintessence
and k-essence context in the Appendix.
