Infinity if it’s a decay series, or 18 years if it’s a constant.
It wouldn't be an infinite decay even in a world with spherical cows because the ice mass is the value decaying and eventually the ice is no longer heavy enough to be called a glacier.
Which makes estimating this particularly tricky (and pointless) because there's no obvious point at which a mass of ice turns from "glacier" to "not glacier". Better to pick something erring far towards "totally obviously not glacier" as a reference point.
Sorry to break it up to you, but the warming is accelerating, as the amount of GHGs is increasing year-by-year. So it may take even less.
Climate and weather are cyclic, not linear.
The increase in CO2 is linear and as long as that continues to be the changes will be linear or higher.
What increase? EPA says USA has reduced CO2 emissions over past quarter century.
The USA offshored it. And the USA is not the entire world.
Their prices are artificially low due to their manufacturing pollution which negatively affects the entire world. Maybe consider environmental parity tariffs against those polluting countries. Or is The West too addicted to cheap stuff?
Would it ever reach 100% in anything short of a runaway greenhouse scenario?
Why wouldn't it? The glaciers on the Kilimanjaro are expected to melt completely in the next few years.
I guess that depends on the definition of a glacier. If the ice/snow completely melts then I assume that would count as 100%. Even if it is replenished the following winter, if it all melts again the following summer then I don't think anyone would call that a glacier.
The last time we think Earth was completely ice free was 35 million years ago.