re (1.) It might not be that easy. Sure, the planet would cool down again, but - the 1000 year ocean cycle takes time, (which is now transporting heat and carb

re (1.) It might not be that easy. Sure, the planet would cool down again, but - the 1000 year ocean cycle takes time, (which is now transporting heat and carbon into the lower ocean layers) - building up the ice sheets again takes way longer, and ice sheets are important to the albedo, thus also have an influence on climate, - there are some points where something big might change, such as ocean current patterns changing permanently(due to changes in heat and salinity distribution), permafrost thawing and releasing huge volumes of methane, .. It's a massive problem to undo. Right now it'd be still relatively easy, but it might not stay that way. (We'll have to learn how to control the climate longterm anyway since another ice age would be desastrous, but it's too soon. We're still to unknowledgerable and weak.)