I thought about adding that but I imagine that will actually turn out to be something of a wash. While it will release heat to the cooler layers surrounding the core, it will not and cannot transfer heat to the hotter core.
I was trying to stick to those things that could heat the interior. The surface warming actually probably should have been included in the same category as phase changes, increasing the temperature and so insulating the core. Afterall, as two objects approach equlibrium it gets increasingly harder to transfer heat.
Aslan is not a Tame Lion