1. In this story, @JohnMuyskens and I looked at @gcarbonproject data to see when emissions have actually declined notably in the past. The answer is "world wars, sweeping economic contractions or large-scale geopolitical events such as the fall of the Soviet Union."
2. If recent trends continue -- with emissions in China down by a quarter in recent weeks, and oil markets and air travel showing disruption around the world -- the novel coronavirus could join this group. But it's very early to say for sure.
3. The upshot is that at least up until now, only major events of upheaval have been sufficient to stop the world's emissions growth. Or as @Peters_Glen put it to me, "whatever the driver, it will have to be big, and global."
4. Whether coronavirus fits this category depends on the length of its impact and how much economies bounce back -- including through major stimulus measures -- once people and world leaders feel the situation is more stable. So, really remains to be seen. /end
