I do wish people would stop posting this silly graph. It only goes back 20,000 years, blink of an eye in terms of the planet's history, and I am guessing deliberately chosen because this period has been relatively stable, which is not actually typical at all. If you look at the overall picture the planet has been a lot warmer than it is now for well over half the time we can estimate temperatures for. And there have been large short term spikes going back over millions of years, long before they can conceivably have had anything to do with us. So yes we are undoubtedly contributing to the rise in temperatures, and consequent climate change, and we should stop these aggravating activities as soon as we can. But I think to suggest that it is ENTIRELY a man made phenomenon is probably wrong. We are an arrogant species and very fond of looking at everything from the point of view of our, very fleeting, existence. How long have modern humans been around, and in sufficient numbers to do anything, 50,000 years? That is probably generous. If we talk about organised civilisation it's only around 5/6 thousand years. Dinosaurs were around for over 150million years, and it was a lot hotter for most of that time, as it has been for most of the time since life evolved. There have been umpteen mass extinctions, where in some cases over 90% of life became extinct. These were entirely natural phenomena. True we are without doubt the most destructive creatures ever to have evolved, with a wanton disregard for every other species, plant or animal. So if we don't buck our ideas up will will probably exterminate ourselves, but the earth will undoubtedly carry on, and all remaining species will probably think good riddance.