Doesn't increased human activity add to heating the atmosphere directly?
It does, but globally it's negligible compared to other heat flux densities.

Simply do the math:


World wide primary energy consumption: 162,494 TWh (2018)
Hours/year (2018): 8760 h
Earth surface: 510,100,000,000,000 m²


Assuming all this energy is transformed to atmospheric heating, this is an average heat flux (q=E/t*A) of 0.036 W/m². Locally this varies widely depending on climate (and the necessity to heat or cool buidlings), the degree of industrialisation, the population density etc. One figure I've found in Wikipedia for Germany: 1.2 W/m², Antarctica obviously: more or less 0.0 W/m², Hongkong (2018) 40.2 W/m² (calculated myself). BTW the average geothermal heat flux is 0.087 W/m².

Compare this to the solar contant: 1361 W/m². Considering albedo, day &amp; night etc. the average (solar short wave) flux density on Earth's surface is ~ 175 W/m². The atmospheric back radiation is ~ 300 W/m².

So the average solar short wave flux density on Earth's surface alone is ~ 4,850 larger than the heat flux density directly induced by human energy consumption.

The heat flux density indirectly induced by human energy consumption (CO₂-, CH₄-, N₂O- etc. accumulation in the atmosphere) currently adds up to netto ~ 2.3 W/m² additional back radiation, which is roughly 60 times larger than the directly induced heat flux density.



Conclusion: direct heating of the atmosphere caused by energy consumption is almost insignificant compared to other effects.