If you find and upward trend in the timberline over recent years, this means the climate is getting milder nowadays right? Does this mean global warming is really happening?

Hi Stuart,
You are right, an upward trend is due to a milder climate; however, the question what to understand under global warming is more difficult to answer. If we look at the big picture the climate on earth has changed quite drastically - just think of Hannibal crossing the alps with elephants in Roman times. We have evidence that it was warmer then, than it is today. Going along with higher reaching forests. About 150 years ago it was very cold - a little ice-age. Climate is therefore changing in intervals and whether we are still on an upward trend after the little ice-age or we have global warming (this expression nowadays indicates the human influence)is difficult to say. We are working hard to seperate the signals we get from the trees to be able to quantify the human and the natural warming.