From what I remember (it’s been over a decade since I read it), the southern hemisphere has much more water than the north.
Water is a great heat battery, especially deep oceans. And there’s a gigantic mass of water in the south. So in the summer it stays cooler because that mass of water can store a lot of energy, and in the winter it stays much warmer because the oceans slowly releases the heat that they have stored.
All that water mass is essentially “dampening” the climate extremes. And since ocean water also slushes around + evaporates in much greater mass than the little water on land, heat also gets redistributed better than on land.
So in short: more water = cooler in the summer + warmer in the winter.
Russia wouldn’t even have had to capitulate, a white peace and some empty diplomatic gestures from Ukraine (like signing a piece of paper in which they promise to “denazify”), would have been enough to get a peace that Russia can sell at home. The classic power play of “we’re going home because we accomplished all objectives, we’re definitely not running away with our tail between our legs”. But Putin would rather see hundreds of thousands of Russians die, just so he can pretend one more year to never be wrong about anything.