Asteroid Impact: A large asteroid collision could cause massive destruction, triggering tsunamis, wildfires, and a prolonged "impact winter" due to dust and debris blocking sunlight.
Nuclear War: A full-scale nuclear war could result in widespread destruction, radioactive fallout, and a "nuclear winter," significantly disrupting the climate and food production.
Supervolcano Eruption: An eruption of a supervolcano, such as Yellowstone, could release vast amounts of ash and gases into the atmosphere, leading to a significant drop in global temperatures and widespread crop failures.
Climate Change: Unchecked climate change could lead to catastrophic effects, including severe weather events, sea-level rise, loss of biodiversity, and large-scale disruptions to human societies.
Global Pandemic: A highly lethal and contagious pandemic could decimate human populations, disrupt societies, and cause long-term economic and social instability.
Artificial Intelligence: If AI systems become uncontrollable or are misused, they could pose existential risks, potentially leading to scenarios where human safety and survival are threatened.
Gamma-Ray Burst: A gamma-ray burst from a nearby supernova could strip away the Earth's atmosphere, exposing the surface to harmful radiation and making the planet uninhabitable.