the sun itself is not responsible for global warming, it must be that the temperature is changing due to climate changes. Anyone?
The energy input of the Sun stays constant (mostly, there are some minor variations), so no, the Sun is not responsible for climate changes.
The temperature of the Earth has to do with the balance between the energy input, and the energy radiated back into space. If the temperature is not changing, they are the same. Global warming is caused by gasses in the atmosphere limiting the energy radiated into space, therefore, the temperature rises, until the energy radiated is again equal to the solar energy input.
Actually the sun's output over time does vary, and it does cause climate changes. There is an 11 year cycle as shown in this image from www.sciencemuseum.org.uk:
And in the early half of the 20th century it did increase slightly, which probably did contribute to global warming during that time but over the last 50 years it has actually slightly cooled, so it is absolutely not responsible for the global warming we currently see. This image (from the same source) shows some nice detail. The dotted line is the moving average: