Of course the sun has something to do with warming the earth. But the changes in the sun's output are not enough to explain the increase in temperature. Carbon dioxide slows the rate of heat loss back into space, and the increase in carbon dioxide is the only way to explain the temperature increase.
I may be mistaken, but the 0.8C is the current increase we have already seen. Look it up.
Global Surface Temperature Trends | Center for Climate and Energy Solutions
Climate Change: Key Indicators
We were not alive in all those past conditions - and we would not want to have been. We are alive here and now, along with all the other life forms that have adapted to the nearly steady state of 170-270ppm carbon dioxide, for ~650,000 years.
And of course the arctic has greater than average temperature rise - what else is causing the ice to melt so fast? Physics dictates that if you slow down the heat loss by adding more "insulation" in the form of carbon dioxide - things will get warmer.
It's not doomsday stuff - it is reality. We know it because we see it. The data shows us reality, and we can compare it to the past events. We know we will be in a heap of trouble if we continue like we are.