Many nuclear advocates seem to share this misconception. Fighting climate change is not about simply switching all power generation to one and only one alternative source. It's not about whether we are going to rely 100% on nuclear or 100% on solar, and it's not even only about generation.
A large part of the efforts are focused on things like increased efficiency. Alternative energy also plays a role (including nuclear, though it plays a relatively small role). These efforts will help cut emissions until we get below 450 (or 350), not entirely eliminate emissions. We don't need solar (for example) to provide electricity 24/7 - we need it to help decrease the emissions. If we have enough elements that decrease the emissions some amount, we'll eventually get below 450 (or 350).
There seems to be a fundamental misunderstanding by some about what the fight against climate change actually entails. It is not about picking the one and only energy source for the future.
> The deficit we face is merely one of will
This ignores the economic and construction issues that nuclear plants have.
Engineering problems with known solutions, were we only to implement them.
> There seems to be a fundamental misunderstanding by some about what the fight against climate change actually entails.
If that's so, it's a result of the rhetoric employed by many on the conventional, non-nuclear anti-AGW side. For example, you're the first person I've ever heard espouse this kind of incrementalism on CO2 figures. For most rhetoric on the subject, "apocalyptic" is not too strong a term.
I think a lot of nuclear advocates adopt their position on the basis that it's the most effective available response if things really are that bad. And then we get confused when people would rather keep technologies that spew filth constantly into the air, instead of accepting a very slight increased risk of localized and contained industrial accidents which are costly but not deadly. (Yeah, I know: Chernobyl and Fukushima. No one is proposing we build RBMKs in the US, and unlike Japan, if we want to build 2nd-gen BWRs safe from tsunamis, we have ample inland territory on which to do so.) If it's a choice between nuclear power and civilizational collapse involving megadeaths, that seems like a no-brainer. If it's not such a choice, it's fair to ask why so many people have done so much to make it seem so.
Honestly, I think the environmental movement has shot itself in the foot here in a huge way. Decades of painting nuclear power as Satan incarnate has made it politically impossible, indeed unthinkable, to include new, safe nuclear as the foundation of a strategy addressing AGW with a truly sustainable generation architecture, so what we're left with is quarter measures and cheese-paring fractionalism - changing lightbulbs to save the world.
Here in the US, we're not constrained by fuel shortages, and we don't have to make ourselves beholden to a potentially hostile foreign state in order to take advantage of the AP-1000 design. We also have the world's broadest and deepest reservoir of institutional knowledge on the subject of nuclear power - a technology invented in the United States, and which we have arguably developed to the greatest extent of any nation on Earth, even if we have thus far chosen not to reap the full benefits of our efforts.
You're right that we aren't building out modern nuclear technology as well as we could be. But we aren't facing the same structural limitations China is, and we therefore do not face a similar choice between unpalatable options. The deficit we face is merely one of will - that is, we're not building out new nuclear because we can't, but rather because the very same people who inveigh most strongly against ignoring AGW have an ideological and frankly emotional objection to modern nuclear infrastructure, an objection which arises entirely from industrial accidents which occurred with technology now half a century old, and from which the industry has learned.
To be quite clear, I have significant concerns of my own with how new nuclear is likely to be implemented. Specifically, as I've stated in this forum and others, the existence of a profit motive around the operation and safety management of nuclear reactors is in my opinion a substantial risk. That risk is, however, susceptible of mitigation or elimination by quite realistic measures, and even if left completely as is, collapses into negligibility alongside the risks posed by either continuing to ignore AGW, or building a response that relies entirely on ill-tested, seasonally variable, and enormously inefficient power generation methods to supply life-critical baseload power.