Instead of trying to understand the temperature control system for earth, we should image earth without a temperature control system and then design one. If I were given the task of controlling the temperature of earth, I would ask God, or Mother Nature, or a Scientist or an Engineer to design a system. Of these, God, Mother Nature and Scientists work on their own agendas, so I would give this task to an Engineer. I have no control over God, Mother Nature or Scientists, but I can hire an Engineer to solve a problem. An engineer would say: This is a temperature control problem, for a robust system we need a substance that changes states in the temperature range we need. We need a lot of it. We would not consider using a wimpy trace of something. We need a way to warm it and we need a way to cool it. We need a huge heat source and we need a way protect it from the heat source. We need a system that can cool when we are hot and that will stop the cooling when we are cool enough.
Water, in its states with the powerful temperature set point between ice and water and the water vapor and water drops and ice particles in clouds, along with the ocean currents and the atmosphere wind currents and ice albedo on the ground make up the system that keeps the temperature of earth in narrow bounds.
When earth is warm and the water is liquid, a huge amount of the water gets into the atmosphere and cools earth with reflective clouds and increasing snowfall and increasing ice albedo. When the earth is cool enough, the water does freeze and cut off the water from the atmosphere. Reduced clouds allow more solar energy to melt ice on the ground in summer and with much less clouds there is no way to replenish the ice in the winter.
When the earth is warm enough, we repeat the cooling cycle.
When the earth is cool enough, we repeat the warming cycle.
This is the way an engineer would control the temperature of earth. This can be accomplished without CO2. This can not be accomplished without a huge amount of Water and all its states. The orbit parameters and the arrangement of continents and the amount of water is important to keep us in Paradise.
The engineer would likely throw in a trace of CO2 to help the green things grow and help conserve the fresh water. That makes the earth look better and provides food and creates fossil fuel. It may influence the energy flow, but it is only a trace and easily overpowered by the overwhelmingly more abundant water in all its states and powerful set point. This system includes and uses Water Vapor, the most powerful of the Greenhouse Gases. The minor Greenhouse Gases are of minor importance.
This page was inspired by a trip to Idaho, an Airplane Flight in the Mountains, discussions with Nuclear Engineers, an Electrician, Airplane Pilots, a Power Plant Operator of numerous kinds of plants, random other people and a visit to EBR-1, the Atomic Museum of the Worlds First Nuclear Power Plant. When you need to deal with huge amounts of heat, you need a huge, powerful cooling system with quick response.