Yes, we could say that without the additional warming effect from anthropogenic greenhouse gases (AGW), the perceived temperature after sunset might feel cooler due to several factors:

1. Radiative Cooling: With lower concentrations of greenhouse gases like CO2, less infrared radiation is trapped in the atmosphere, allowing more heat to escape to space. This would result in a cooler effective sky temperature, enhancing nighttime radiative cooling.

2. Effective Sky Temperature: The estimate we discussed earlier suggested that reducing CO2 levels from current to pre-industrial could lower the effective sky temperature by about 2 to 3°C. Even if we conservatively estimate that only part of this reduction directly affects how cool it feels due to radiative transfer, we're still looking at a notable change.

3. Perceived Temperature:

   • Before Sunset: Without AGW, the day's temperature might not be as high, but let's focus on the post-sunset scenario where the absence of solar heating means radiative cooling becomes predominant.
   • After Sunset: The temperature drop would be more pronounced:
     • With AGW, the warmer atmosphere retains more heat, which is radiated back towards the ground, making nights warmer than they would be without this effect.
     • Without AGW, this extra warmth isn't there, leading to a faster and more significant cooling after sunset. The drop in temperature could indeed make it feel 1 to 1.5°C cooler, perhaps more, depending on local conditions.

4. Factors Influencing Perception:

   • Humidity: Lower temperatures might also come with changes in humidity, which affects how cool it feels. However, in this simplified model, we're focusing on temperature alone.
   • Local Environment: Urban environments might not feel as much of a difference due to the urban heat island effect, which can mask some of the cooling from reduced greenhouse gas levels.

5. Global vs. Local Impact:

   • Globally, the average temperature has already risen due to AGW, so removing this effect would lower the baseline temperature. The exact drop in perceived temperature would vary by location, with places like deserts potentially experiencing larger differences due to clear skies and lack of moisture.

So, in summary, without AGW, the radiative cooling effect would likely be more pronounced after sunset, making the environment feel cooler by roughly 1-1.5°C or more, as the atmosphere would be less effective at trapping the day's heat. This would be particularly noticeable in areas with clear skies and lower humidity where radiative cooling is most effective.

@GeraldKutney I've just had a lengthy conversation with Grok with some quite interesting result