Had we depended solely on experiment for everything, we would know much less about the world today. When direct experiment is not possible we still have observation and modeling, and certainly that is science. And of course most of our models do scale, simply because of long observation at all scales. Were this not the case, we would still be arguing about the heliocentric theory, because we can not move planets and suns in order to prove it from first principles, and the orbits of planets would not necessarily scale to suns, etc.
Sure, the earth has large processes that regulate each other, but there is nothing purposeful in their existence and positive feedback is as likely as negative. The Earth is as likely to be naturally fragile as naturally robust. So you can not place faith in unseen processes that will tend to mediate insults to the environment.
If there is some unknown non-anthropocentric cause for climate change, we are still in the position of having to resolve the issue through some modification in society's behavior, rather than consign the victims.