A recent paper published in the Journal of Climate examined satellite records over the West African Sahel to determine that clouds caused a yearly average decrease in shortwave radiation [solar radiation] at Earth’s surface of -83 W m-2 [due to blocking incoming solar radiation].
The paper also finds clouds clouds caused a yearly average increase in longwave radiation [radiation from the 'greenhouse' gas water vapor] at Earth’s surface of +37 W m-2. Thus, the average net radiative effect at the surface would be -83 + 37 = -46 W m-2. This would indicate that clouds exert net negative feedback to cool the climate. Climate models, however, assume clouds act as a net positive feedback to warm the Earth.
The paper also finds cloud effects are very poorly represented in climate models, noting, “Both [global climate models tested] underestimated the surface [longwave] and [shortwave cloud radiative forcing] and predicted near zero[shortwave cloud radiative effect] when the measured values were substantially larger (70 Wm−2 maximum).”
This paper and many others [including one also published recently in the same journal] show that cloud effects are very poorly represented in climate models and are of the opposite sign to observations.