Solar Storm (CME Outburst) - Ability to overload electric appliances, including Cellphones, Computers, Electric Transformers, etc. Certainly will change our lives for a while Yellowstone Eruption - If looking at a VEI 8 Eruption Scale, 2/3 of the United States would be decimated by volcanic debris. Can cause a global cooling in climate if enough Sulfur and Carbon Dioxide emitted into the atmosphere reflect enough rays of light back into space. Nuclear War - If we're looking at every single country that are in possesion of Nuclear weapons firing at each other, it would devastate the environment and climate, and may affect electric appliances from EMP rays from the mushroom cloud of a nuclear explosion. Global Warming - In Debate as if we're actually the main cause of temperature rise, but we may be speeding it up much faster than naturally, which would give less time for species to adapt and survive. Can cause major ice areas to melt, less preciptation during summer and more during winter, destruction of ecosystems from over-development and floodings.