These people completely ignore water vapor and focus solely on CO2. They’re so stupid.
The oceans are warm, this causes higher moisture in the air and warmer low temperatures - especially in arctic regions. The moisture is transferred into snow because there’s more water vapor in the air, which draws more ocean from the sea. Eventually the cycle will break down and we’ll have colder air in the arctic again that generates less snow.
It all has to do with water vapor and the sun’s activity.
Yes, the only real external variable in the system is the Sun. Everything else, including carbon levels, are completely an internal variable in an otherwise closed system.
Now, the level of carbon in the system can vary where it is located, whether in the rocks, the atmosphere, or the oceans, and sometimes it can be locked up somewhere on a very long-term time scale, but all of that carbon was always there on the planet somewhere. Humans haven’t created a single molecule of it.