It's worth reading the full article — the big concerns are that:
- We're not living in the worst-case scenario, but it's still necessary to get emissions down to zero
- large-scale negative-emissions technologies are pretty unlikely, so it's more important to end fossil fuel use than the models indicate
None of this in any way reverses the idea that if we actually got to zero emissions, we'd see temperatures stabilize, or that it's impossible to do just that.