“The fact that renewable energy is failing to decarbonize the electricity sector may surprise many readers accustomed to breathless reports of the rapid growth of renewable energy around the world. What Christophers means by this, though, is that while renewable energy is growing rapidly in many places, these increases are not even keeping up with global growth in the demand for electricity.”
The point being made in the article is that there is no meaningful substitution, just additional generation, while the total emission volume is still growing. At least, until the fossil extraction falls off the cliff, apparently out of the blue.