Frozen Dinners and My Carbon Footprint: A Question

[Rain Man]

If I bring my frozen dinner (lunch, to be more precise) in to the office, I have two options for storage. I can put it in the freezer until it's time to nuke it, or I can leave it on my desk.

Let's examine a situation in the summer. Some little lump of coal is working to provide air conditioning to my office, so it makes a lot of sense to leave my frozen dinner on my desk. The dinner thaws, which cools the office and simultaneously requires less microwave energy when lunchtime arrives, and on top of that no lumps of coal are used by the freezer to keep the dinner frozen for those four hours. I'm being a responsible citizen and I'm increasing the Coal Era by another 1/1000th of a second. Everyone wins.

The real question is the winter. Let's say that it's 20 degrees outside. Now a little lump of coal is working to heat my office. If I leave my frozen dinner on my desk, it takes less microwave power at lunchtime and less freezer power (I think), but at the same time it's working in opposition to the office-heating lump of coal. Or does it take less freezer power? If I bring it straight from home it's still frozen, so as long as it doesn't heat up over the temperature of the freezer it would actually help cool the freezer. This is another unknown.

In the other option, if I put my frozen dinner in the freezer during the winter, will the freezer use more or less energy before lunch? I'm not sure. We do know that it'll eventually take more microwave power to cook it, but then again it won't be cooling down my office, which needs heat.

So in winter should I put my frozen dinner in the freezer or leave it on my desk? I want to minimize my carbon footprint.