Emergence and Empiricism

This one is too cerebral for Qualia (but I am going to rework it for them):

In the gray of a late '70s northern Ohio winter, Norman Care led me through Descartes' Meditations on First Philosophy. At the time I really didn't get it, but as I have continued to ponder in the intervening decades, I have come to take Meditations as the origin of the mind / body split and extended that event to the separation of Humans and Nature.  Several centuries after Descartes, John Searle solved the mind / body problem to my satisfaction (to my pleasure even) in his Rediscovery of the Mind by essentially declaring that it is a red herring and asserting that consciousness is simply an emergent property of brains.

So what might be the analog to my extension of the mind / body problem to the Human / Nature problem?  It is an entertaining exercise to think of humans as neurons in an Earthly consciousness, but I usually stop short of taking that analogy too far; none-the-less, it does not seem too far fetched to imagine that there are properties of Earth that are observable, but that are not simple, linear causal / effect relationships.  There are all sorts of Gödelian knots in here, but putting those aside, consider the implications of mistaking an emergent property for a something simpler...

One of my candidates for this sort of thing is the CO2 concentration of the atmosphere.  Observations of that parameter clearly show unbroken increase despite decades of policy wrangling and hand wringing.  Is is unreasonable to think that greenhouse gas concentrations are simply an emergent property of human evolution?  And if this is the case, are linear policy approaches the only solutions we should consider?

I don't know the answers here, but I find the questions fascinating.