It's the difference between a hand-warmer and a coat. The hand-warmer adds extra heat to the system (like the heat from burning fossil fuels). A coat doesn't ad

It's the difference between a hand-warmer and a coat. The hand-warmer adds extra heat to the system (like the heat from burning fossil fuels). A coat doesn't add any extra heat, it just traps some of the heat that would otherwise be lost (like greenhouse gasses). Hand-warmers can keep part of the body warm for a few hours. Coats can keep the whole body warm for years.