Would you live on terraformed Venus?

[Alan V]

Actually, not much worse than the worst scenario of the biggest global warming alarmist.   If we really don’t tamper our release of greenhouse gas for, say, several centuries, we can get into a true runaway green house, which, once started, can not be slowed or reversed by any act of repentance we can currently envision.   The earth will inexorably lose all of its surface water, leaving a largely oxygen atmosphere orders of magnitude thicker than ours now, ready to be converted to CO2. When the conversion is complete, Earth will be a second Venus.

We will not be able to maintain our release of greenhouse gases for several more centuries since we will likely be running out of economic fossil fuels before the end of this one. Further, the radiative forcing for CO2 is the same for any doubling of the CO2 concentration, regardless of how much that is in actual parts per million. This is because the infrared absorption bands become saturated as CO2 increases, so it takes more and more CO2 to warm the average temperature a given amount. So more CO2 will always cause more warming, but at a decreased rate. Due to how much of the Earth's carbon is safely sequestered in carbonate rocks like limestone due to the action of the ocean over millions of years, even with the release of carbon from the permafrost and from methane hydrates in the ocean, it would not be enough to lead to a runaway greenhouse effect. However, another major extinction of species would be very likely with that much warming over a relatively short period.