People get a D− for reading comprehension on this one.

The scientist said¹ that unless we stop using fossil fuels within the next five years, climate change will wipe out humanity -- that doesn't mean it will wipe out humanity by the end of the five years. It means that the process will be unstoppable if we don't do something about it within five years.

Examples:

• I just got blasted with a huge dose of radiation. If I don't get a complete bone marrow transplant within the next five hours, I will certainly die -- but it might take me another four or five days of agonising radiation poisoning before I die.

• I'm driving really fast towards a bridge which is out. It takes at least 200m for me to brake and stop the car, and I'm 700m away from the bridge. If I don't start braking within the next 500m then I'll go off the bridge -- but it doesn't mean that I go over the bridge the instant I hit the 500m mark. It just means that once I reach that spot, there's not enough distance to stop before I go over the bridge.

I don't know if the guy saying this is right or not. My personal feeling is that by the end of the century, we'll be dealing with mass environmental collapse, made much worse by war, and there will be megadeaths, but I don't expect the complete extinction of humanity. I expect a few hundred million will probably survive, assuming we're smart enough not to unleash too many nuclear bombs or really nasty war viruses.²

¹ Supposedly. The media often exaggerates what scientists say.

² Yeah, we're doomed.