Die-off. This is when the population and the state of the planet — its average temperature, for example — increase rapidly. Eventually, the population peaks, then drops quickly as temperatures make it more difficult to survive. The planet reaches a steady population level, but it represents only a fraction of the peak. "Imagine if seven out of ten people you knew died quickly," Frank said.
Sustainability. Here, the population and the temperature rise, but both eventually reach steady levels without catastrophic consequences. Once people realize the bad effects of using high-impact resources, such as coal and oil, and switch to low-impact resources, such as solar energy and other renewables, everything stabilizes and life goes on with no further harm.
Collapse without resource change. This occurs when people don't act. The population and temperature both rise rapidly until the population reaches a peak. Then the population drops precipitously. Civilization collapses, although it is unclear whether the species dies out completely.
Collapse with resource change. The population and temperature increase. People recognize the potential catastrophe and make the switch — but it's too late. Civilization collapses anyway.
Jeff Bezos’ $10 billion to fight the climate crisis can make a difference—if spent correctly