Problem with denoising the BICEP2 data?
B-modes in the raw CMB data can be caused by primordial gravitational waves, as well as by cosmic dust. After subtracting the cosmic dust polarization from the BCEP2 data, the residual signal is too weak with respect to noise to be statistically sufficiently significant to claim a discovery.

Or stated in a different way: The observed B-modes can be explained away by cosmic dust.

This doesn't prove the absence of primordial gravitational waves. But it doesn't provide sufficient evidence for their presence either.