Two "Dooms" that are inevitable.
1. Doom by peak oil
I still think peak oil will cause huge problems, when it finally happens. It won't be long until Ghawar peaks in KSA and the world will lose 6 mm bbls/day of oil from that one field. As additional supergiant legacy oil fields peak and then decline, there will come a day when fracking shale will not be able to produce enough oil to keep up, and we'll be at Peak Oil. It will happen 10-20 years later then Colin Campbell predicted, but its inevitable that we are going to hit peak oil eventually. Once the world hits peak oil economic catastrophe is inevitable.
AND Peak Oil could happen next year or the year after that. Waiting for peak oil has been like waiting for Godot, but unlike Godot peak oil will indeed eventually arrive.
2. Doom by anthropogenic greenhouse warming (AGW) and sea level rise.
Greenhouse Warming is coming on faster then most models predicted. We are already seeing bigger droughts and floods and killer heat waves. But I think it will be sea level rise due to AGW that will cause "Doom" in the next 50 years. Even a one meter rise in sea level would cause the abandonment of parts of almost all coastal cities, and the loss of huge areas of densely inhabited deltas in India, China, Africa, the US, EU, etc. etc. Hundreds of millions of people will gradually be displaced. Huge areas of farmland will be underwater. The global economy will be unsustainable.
AGW and global sea level rise are now inevitable.
Sea level rise will result in parts of Boston and other coastal cities being abandoned