Ok, now a question that burdens my environmental conscience. Let's assume that after a number of years there is irrefutable scientific proof - or scientific consensus, if you like - that global warming is not caused by humans but a natural phenomenon, should we try to interfere with nature or manipulate our climate in order to "save" humanity and those ecosystems that are now said to be in grave danger?

If we ever get to the point where the climate is out of control, either because it's the Sun or because mitigation efforts have failed, then I think geoengineering (e.g., manipulating the climate) is the last page of the play book.  In other words, we should turn to it after everything else fails.

Okay, the biggest problem in the scientific world is that when two ideas are presented as the possible reason for a problem only one can be correct. If we to look at this as a combination of many things then the answer can be revealed. Combine the increase of green house gasses, the slight rise in solar ouput, and earths natural history of climate change we can presume that this "global warming" is something that has happened before. In general it is something that the inhabitants of this planet have delt with and survived before.
Also I do like the idea of geoengineering but many questions are raised about the potential danger it could also cause. As humans we are flawed and messing with something that has been around for millions of years can lead to catastrophic events.