The IPCC (The Intergovernmental Panel on Climate Change) climate models assume that the sun has very little effect on global temperature 😂 .

The reality is that the sun is our main source of heat, and solar cycles together with periodic variations in the Earth's orbit and its axial tilt (Milankovitch Cycles) is what causes the temperature difference both in the short term (Winter/Summer) and in geologic ages, apart of course from exogenous causes such as meteorites or supervolcano eruptions.