Check the ice core graphs. Wow. No SUVs, No smokestack industries, No 'overpopulation', bloody little humanity, but the climate has changed even without human intervention.
So what, pray tell would make one think that current changes are being driven by human activity. Those were natural sources driving the past climate changes, without significant human input. But if over 600,000 years of data won't convince you that natural factors are dominant, maybe a paper will, so look here:
http://notrickszone.com/2013/03/02/most-of-the-rise-in-co2-likely-comes-from-natural-sources/#sthash.wyXcO60O.dpbs
Sorry,
@Smokin Joe...I think I'm getting lost in the various replies on the thread. This was an important post.
First thing I'd note is the scale of those old timey pre-man changes...the rates of change have increased.
But let's lay out some points from
your source:
1)
Increasing CO2 leads to an increase in temperature.2)
Increasing temperature of the ocean leads to the release of more CO2.I would agree with these very fundamental points. But note that some on this board are questioning even of these. Perhaps they will trust this source since it comes from you!

Anyway, based on these points, the author claims that the source of acknowledged atmospheric CO2 increase is 10x more likely to be natural...but his analysis ignores several points.
If, indeed, the ocean temperature is increasing from CO
2, then some portion of that increase is anthropogenic. As the ocean warms, it releases more CO
2. Does that suddenly become "natural" CO
2, despite it being ultimately caused by man? (Put simply, he's ignoring feedback mechanisms.)
Secondly, the isotope data imply manmade contributions being important. (I know that it's not clear-cut, but it leans strongly that way.)
Third, is it purely coincidental that the natural input somehow just happens to correlate with human industrial input?

(Note, this isn't the famous "hockey stick" of temperature proxies. This just presents observational CO
2 data from Antarctic ice cores.)
Finally, I submit that it's missing a broader point.
While it's important to understand the sensitivity of the climate to each input, the bottom line is that we
are adding CO
2 to the atmosphere rapidly, and if it affects the temperature (see points above), then that's the factor we have to manage, regardless of source.
A 200-pound man walks to a bridge, carrying 100 pounds...he can't just walk over the 250-pound bridge just because the first 200 is "natural" or inherent... Similarly, if it's determined that we have excess CO
2 going into the atmosphere to meet some decided-upon criterion, it doesn't matter what nature's doing without our control over it...what matters is what we can control (including reducing natural sources, perhaps).