The core question is: "What kind of impact do you expect to make if you work on either issue?"

Do you think there work to be done in the space of solar power development that other people than yourself aren't effectively doing? Do you think there work to be done in terms of better judgment and decision-making that other people aren't already doing?

I'm familiar with questions like these (specifically, from 80000 hours), and I think it's fair to say that I probably wouldn't make a substantive contribution to any field, those included. Given that likelihood, I'm really just trying to determine what I feel is most important so I can feel like I'm working on something important, even if I only end up taking a job over someone else who could have done it equally well.

That said, I would hope to locate a "gap" where something was not being done that should be, and then try to fill that gap, such as volunteering my time for something. But there's no basis for me to surmise at this point which issue I would be able to contribute more to (for instance, I'm not a solar engineer).

To me it seems much more effective to focus on more cognitive issues when you want to improve human judgment. Developing training to help people calibrate themselves against uncertainty seems to have a much higher return than trying to do fMRI studies or brain implants.

At the moment, yes, but it seems like it has limited potential. I think of it a bit like bootstrapping: a judgment-impaired person (or an entire society) will likely make errors in determining how to improve their judgment, and the improvement seems slight and temporary compared to more fundamental, permanent changes in neurochemistry. I also think of it a bit like people's attempts to lose weight and stay fit. Yes, there are a lot of cognitive and behavioral changes people can make to facilitate that, but for many (most?) people, it remains a constant struggle -- one that many people are losing. But if we could hack things like that, "temptation" or "slipping" wouldn't be an issue.

The problem with coal isn't that it's going to run out but that it kills hundred of thousands of people via pollution and that it creates climate change.

From what I've gathered from my reading, the jury is kind of out on how disastrous climate change is going to be. Estimates seem to range from catastrophic to even slightly beneficial. You seem to think it will definitely be catastrophic. What have you come across that is certain about this?