Even if its 100% green energy - which don't get me wrong is orders of magnitude better for warming of the planet - it still contributes to warming of the earth. You're taking some wavelengths of light that would normally be absorbed by say plant matter (thus using that energy to pull CO2 out of the atmosphere) over an area and/or some wavelengths simply reflected out to space without being absorbed by the solar panels (which definitely are designed to absorb as many wavelengths as possible). Then energy conversion from DC to AC and to transmissions lines to where its used all have losses which is energy dissipated in heat form. So the conversion process there can cause heating as well.
Certainly better than combustion which creates heat AND creates gasses which trap that and other radiation as heat.