Often you will hear someone stridently stating that it is only the sun that warms the earth and the minuscule amount of carbon dioxide in the atmosphere has no effect, and therefore the increase in global temperatures is solely due to the increase in the sun’s radiance. There is only one problem with this. It is a lie.
Solar irradiance (the amount of radiation given out by the sun) has peaks around a roughly eleven-year cycle, and these peaks in recent times have been around 1980, 1991, 2002 and 2014. In between these peaks, the irradiance drops by about 0.1%. The maxima in irradiance, also roughly correspond to maxima in sunspot activity and it has an effect on the Earth’s climate, with the maxima warming the planet by about 0.18 degrees Celsius.
This does not explain the increase in average global temperature which, since 1900, has risen about 0.9 degrees C. There is also a clear decoupling of the 11-year average solar irradiance and the 11-year average temperature. That decoupling began about 1970 and has dramatically increased. Since then solar irradiance has actually decreased by about 0.5 watts per square metre, whereas the global average temperature has increased by about 0.7 degrees C.
Figure from: https://www.skepticalscience.com/graphics.php?g=5