The recent BICEP2 measurement of primordial gravity waves ( r = 0.2 ^ { +0.07 } _ { -0.05 } ) appears to be in tension with the upper limit from WMAP ( r < 0.13 at 95 % CL ) and Planck ( r < 0.11 at 95 % CL ) .
We carefully quantify the level of tension and show that it is very significant ( around 0.1 % unlikely ) when the observed deficit of large-scale temperature power is taken into account .
We show that measurements of TE and EE power spectra in the near future will discriminate between the hypotheses that this tension is either a statistical fluke , or a sign of new physics .
We also discuss extensions of the standard cosmological model that relieve the tension , and some novel ways to constrain them .