He walks through a mechanism most people never consider: cosmic dust accumulating in the atmosphere from disintegrated comets. Not a dramatic impact scenario, but a slow accretion that changes everything. When enough particulate matter builds up overhead, it increases atmospheric opacity and reduces the sunlight reaching the surface. That affects photosynthesis at the base of the food chain, which cascades upward through ecosystems. He points to the Little Ice Age as a possible example, a period of cooling that reshaped civilizations across the Northern Hemisphere. But he goes further, suggesting that with sufficient dust loading, the sun could be blocked for several years, potentially triggering a full glacial advance. It is a quiet catastrophe, one that unfolds over seasons rather than seconds, yet the cumulative impact rivals any single impact event.