“Carbon dioxide’s logarithmic heating effect is weak at 100 ppm, tuckered out well and truly at 200 ppm and beyond 300 ppm – well never mind. We are now above 400 ppm from which it is a monotonic 0.1°C for each 100 ppm increase. That doesn’t explain anything and in turn leaves the Sun as the only possible causative agent for the Modern Warm Period.”

https://wattsupwiththat.com/2018/04/09/climate-change-it-was-the-sun-all-along-so-say-the-bulgarians/