It won't be wise - would it ? - to use the EARTH as a laboratory to prove up the concept of what a runaway greenhouse effect can do to a planet.
We don't have to - not that the libertarians/deniers/SF fans among us aren't doing their darnedest to try anyway.
Instead we can just consider the latest science on Venus, a planet somewhat close to us in features, where a classic case of runaway greenhouse gases destroyed any hopes of Life on a planet somewhat similar to ours.
But in the game of Life, somewhat close isn't even close to being good enough : it is the precise/exact/perfect constellation of a dozen or so features that makes Earth that rare - perhaps even unique - planet in the universe with human-like life upon it.
Planets close to being like Earth are expected to number in the trillions throughout the entire universe. But if they have human-like beings all watching TV and playing the internet, we haven't yet detected even the faintest whiff of electronic pollution from any of them.
As Fermi said : if Earth-like planets and Earth-like human beings are so theoretically common : "WHERE ARE THEY ?"
The latest pictures from Mars, a planet even closer to Earth than Venus, in most features, reminds us of how hard it is to get the exact/precise/perfect mixture of features right, to make a place inhabitable.
Without a stable atmosphere and wind currents to even temperatures differences out, Earth would be like Mars - the day side of Earth hot enough to boil all known life - even the most extreme of extreme bacteria -the night side cold enough to freeze all known forms of life - even the bacteria.
Die by day - die by night - die by day - die by night. On and on.
Mars has a winter like Earth, as well - and during that period even the low energy (because unmanned) NASA OPPORTUNITY rover now on Mars had to hunker down, conserve energy and wait it out for months.
It climbed to just the right spot to have its solar panels lined up with the weak low rays of Sun during the long Martian Winter , to give it just enough energy to keep it ticking over.
If OPPORTUNITY was a fungi or a bacteria,we'd call it a 'spore' .
Hardly an attractive place for a high maintenance, high energy using being like us Earthlings.
But for the libertarian Skygods - a paradise - in their dreams anyway.
There is Life and there is SF (F standing for Fantasy) : let us never mis-confuse the two...