The world has agreed to a set of shared targets on climate change. Those targets require deep (80 to 100 percent) decarbonization, relatively quickly. What’s the best way to get fully decarbonized? In my previous post, I summarized a raging debate on that subject. Let’s quickly review.

We know that deep decarbonization is going to involve an enormous amount of electrification. As we push carbon out of the electricity sector, we pull other energy services like transportation and heating into it. (My slogan for this: electrify everything.) This means lots more demand for electricity, even as electricity decarbonizes.

The sources of carbon-free electricity with the most potential, sun and wind, are variable. They come and go on their own schedule. They are not “dispatchable,” i.e., grid operators can’t turn them on and off as needed. To balance out variations in sun and wind (both short-term and long-term), grid operators need dispatchable carbon-free resources.

 Deep decarbonization of the electricity sector, then, is a dual challenge: rapidly ramping up the amount of variable renewable energy (VRE) on the system, while also ramping up carbon-free dispatchable resources that can balance out that VRE and ensure reliability.

Read more: Is 100% renewable energy realistic? Here’s what we know. – Vox