Not so fast...
Yes, it was Sagan who announced the runaway greenhouse theory as explaining why Venus is 700 F at the surface -- at the pole and equator.
Curious -- this was AFTER the Mariner probe confirmed Velikovsky's prediction that Venus was very hot.
In the 1950s astronomers believed that the temperature at the surface of Venus was rather cool -- comparable to earth. The first probes to Venus proved them wrong and Velikovsky right.
When Sagan made this pronouncement the vulcanism on Venus was not yet known. Which today makes Sagan look silly. No runaway greenhouse can cause vulcanism over 100% of a planetary surface.
FYI I was correct when I stated that Venus' retrograde rotation is indeed opposite the other planets. The assertion that this was caused by a collision is laughable. Face the fact -- it is an anomaly and has never been explained.
There is another unexplained anomaly as well regarding Venus' rotation: Venus is in resonance with the earth. Venus always shows the same face to earth at their nearest approach. Again - this has never been explained.
You mistake pronouncements and opinions as facts -- when the truth is they are unproven.