How much longer until World War III?

In the past, when wars erupted, if you were smart enough to take your family to seek refuge deep in the mountains and forests, you could survive. After a few years of calm, you could emerge without issue. Now, however, any major conflict would escalate into thermonuclear war. The entire planet would become contaminated—the soil poisoned, the water undrinkable, even plants and trees turning deadly. Humanity would face its apocalypse. Only a handful would survive, and their lives would be brief. Then, Nibiru would return to Earth, re-creating humanity anew.