43 inches, you are talking about different scenarios and different causes.
- What is happening now is not related to coming into, or going out of an ice age. There is a 100,000 year Milankovitch cycle which does affect climate due to eccentricities in the Earth's orbit around the sun, however the climate effects of this cycle are greater than expected. The large 100,000 year fluctuations also don't go back more than about a million years. Why this is so is not fully understood yet, but it has nothing to do with the current problem.
- What CO2 levels and temperature anomalies were in the past is irrelevant. There were not 6 billion humans and megacities 500,000 years ago. The world and its inhabitants 500,000 years later is a very different place.
- What is concerning scientists is the rate of change, and the cause of that change.
The cycles you refer to occurred over very long periods of time. What is happening now is occurring over an incredibly short period of time, unmatched in the historical record. Not only that, there is no reason to believe it will stop, unlike other CO2 and temperature increases.
The reason scientists do not believe it will stop and/or reverse, is simply because we continue to pump greenhouse gas into the atmosphere unabated. It really comes down to very simple laws of physics: you keep adding it, and it will keep warming above and beyond the Earth's ability to naturally absorb it. It's so simple, yet so many people don't get it.
Originally Posted by ultralights
carbon is Not and never will be "pollution"
On exactly what basis do you arbitrarily decide whether or not something is "pollution"? What's your definition of "pollution"? Do you think pineapple juice is pollution? Would your goldfish think it was pollution if you poured a couple of litres of it into his tank? Yeah I know goldfish probably don't "think", but I'm sure you get my point.
What comprises "pollution" depends very much on what effects a given substance has on a particular environment under certain circumstances. It doesn't just have to be black soot.