There are still quite a few people that believe CO2 has not impact what so ever on climate. It does, but since CO2 is a bit player you have to really hunt of a hint of a CO2 signature in all of the noise. CO2 also has a greater impact is the dryer portion of the atmosphere and over land mass since that is a drier portion of the surface. To dig out a "signature" you can difference the satellite temperature data for the land and ocean. That removes a bit of the noise that just a part of climate. Then using a satelite era baseline with the least noise, 2000 to 2012 for example for both the land-sea difference and Mauna Loa CO2 you can compare the slope. 0.8 C should be the CO2 impact based on the Kimoto energy balance method so here is the comparison.