I found a calculator for what it would take to warm the planet Mars with a certain amount of CO2.
What I found was it took an insane increase in CO2 (about six times the increase that we've seen on Earth) to warm Mars up 5 degrees.
I think it is the situation on planet Venus where atmospheric pressure is 100X earth and much of that is CO2 that caused all this intellectual activity among the Algores and other New Agers. Runaway greenhouse effect they say and worry earth could become like that. That's what they told us in grammar school in the 50s when they also said we had world oil reserves for 20 years. I remember back then that many of my fellow fifth graders were already skeptical of much that we were told and sometimes wonder if they have become rank and file True Believers through dietary effects on their ossified brain lobes.