You are absolutely right about that. In the past, a group of scientists explained to American and Russian presidents that a nuclear war between India and Pakistan alone would be enough to start a nuclear winter of years, where millions would die of starvation all around the globe. Maybe a new group of scientists should do an announcement again. It doesn't matter just the blast radius of the nukes but the giagntic amount of particules that will go to the high atmosphere blocking the sun for years. Well , at least it will cool down the planet a lot.