Global warming

[cliffie47]

Is global warming caused by solar radiation or greenhouse gases? Is there any evidence of increased solar radiation?

[newtron]

The way I understand it is based on an energy balance.  Solar radiation enters the atmosphere and hits the earth.  Some of this energy is reflected back out of the atmosphere.  Greenhouse gases tend to trap this heat so that it cannot escape the atmosphere, causing temperatures to rise.  I don't think there is an actual increase in solar radiation input from the sun.