This graph shows how the UN predicts what would have happened without the Paris pledges. And it shows what is probably a more realistic prediction becauseit takes account of the burst of CO2 from 2002 to 2010 was due to China. China decided to stop that for health reasons, not because of COP21. So without any help from the UN, the world would go back to what it was doing before China lethal CO2 burst.
So, using this more-realistic and lower prediction of business as usual up to 2030, pledges (INDCs) are really about the same as what would have happened anyway. COP21 had nothing to do with it.
Of course, we are still grateful that China has stopped it’s CO2 burst. But that does not mean COP21 is succeeding. In fact countries are just pledging what they would do anyway, and that will continue in subsequent rounds of pledge and review.