RE: skipping for body fat loss
It would be far from my choice of cardio... although this is personal preference, i find it causes my shoulders to tense up too much if done for any length.
It simply comes down to what sort of pace you can maintain whilst skipping. Too intense and you won't burn much fat.
Also, as you may or may not know, you can't just burn 'belly fat', the fat will be burnt all over.
For fat loss i would recommend cardio sessions longer than 20 minutes, more like 30 mins at an absolute minimum and upto 60 minutes if required.