Do these projects use increasing amounts of space on my disk? climateprediction.net is using >12gb of space on my disk. Seems excessive. Are old tasks not cleared?

Don't know what you mean by 'dead slots'? Could you explain?

I only have two slots, and they're pretty empty, but there's a Projects folder and I found that it has a bunch of stuff under climateprediction.net, most of it dated to earlier than today. I'm pretty sure I could safely delete this stuff, as it looks like old tasks. Do you know if that's true? No problem if you don't know, maybe I'll take the chance anyway.
Rosetta has only a few folders, malariacontrol a few files. They both report low disk usage. So, this does look like the culprit.

Thanks for your help, by the way. I was completely lost until you replied.

Definitely it. Just deleted everything, climate prediction is now using 168mb, and chugging away nicely, didn't even notice those files got deleted.
Thanks for the help!

I've looked in my CPDN Projects folder. As well as the subfolders for my current climate models there are a lot of files for model types I've run in the past but am no longer running. I could delete these without affecting my running models.

But if these previous model types became available again and I downloaded them, the downloads for the first model of each type would be large, as if I'd never run them before. Downloads for subsequent models of each type would be smaller.

The HadAM3P model has particularly large files, about 120MB altogether I think for an initial download. Downloads for subsequent models of the same type are I think about 80MB.

So if you intend to run a model type again if it's released again, it's better to leave the files in place.

Every model type could be released again with different initial values for a new student's experiment...