Nuclear War May Stop Global Warming?

Sorry, what? In 2006, National Geographic posted that, "Even a small nuclear conflict would cause long-lasting global devastation that could kill tens of millions, scientists warned this week."

Then last week, they posted that, "Even a regional nuclear war could spark "unprecedented" global cooling"

Sorry, what? Is global warming such a concern that 'long lasting global devastation' is a reasonable risk?

Hat tip to FerFal for the pointer.