Considering the weak luminosity of the early Sun, it is generally inferred that high concentrations of greenhouse gases (CO<sub>2</sub>, CH<sub>4</sub>) are required to prevent the early Earth's surface temperature to drop below the freezing point of liquid water. Conversely, a new controversial assumption based on banded iron formation mineralogy hypothesizes that the Archean atmosphere was potentially characterized by low concentrations of CO<sub>2</sub>. To solve the faint young Sun problem, it was suggested that a reduced albedo associated to less reflective clouds was able to prevent the Earth to jump into a snowball state. In this very active debate, we have investigated the early Earth climate using a general circulation model to test this scenario. Our simulations include the ice albedo feedback and specific Archean climatic factors such as a different cloudiness, a faster Earth's rotation rate, and a reduced continental surface. We demonstrate that when larger cloud droplets are accounted for, clouds warm high latitudes and inhibit sea-ice formation. This process limits the ice-albedo feedback efficiency and may prevent a global glaciation. Due to this particular mechanism, low <i>p</i>CO<sub>2</sub> allow maintaining a mild climate during the early Archean. This conclusion will be challenged in the second part of this paper, where the carbon cycle is considered.