No. The sun can influence the Earth’s climate, but it isn’t responsible for the warming trend we’ve seen over the past few decades. We know subtle changes in the Earth’s orbit around the sun are responsible for the comings and goings of the ice ages. But the warming we’ve seen over the last few decades is too rapid to be linked to changes in Earth’s orbit, and too large to be caused by solar activity. In fact, recently (2005-2010) the sun has become less active, while temperatures have marched upwards.
One of the “smoking guns” that tells us the sun is not causing global warming comes from looking at the amount of the sun’s energy that hits the top of the atmosphere. Since 1978, scientists have been tracking this using sensors on satellites and what they tell us is that there has been no upward trend in the amount of the sun’s energy reaching Earth.
Click here for the sun's energy charted against global temperatures.