"Sorry, that stopped me in my tracks. You're wrong Tom. If you could show me a single data point that showed atmospheric CO2 levels what they are now in the last million years, I might be more prone to sitting on the fence."

Rising CO2 levels do follow warming. That is known. But they seemed to have followed by quite a considerable time [hundreds of years] after the warming. You could argue that our warming period is longer than the normal so this longer duration could be factor in causing higher levels. Now, if oceans are the source of this CO2- and thereby explain the long time lag, it's unlikely any very recent increase in CO2 is due to the short term cooling of the ocean and in addition I don't think over the last few hundred years the ocean has warmed significantly. If the arctic was a primary source, then one would think the various cooling and warmer trend [say in last 100 years] of arctic would be reflected in the CO2 record.
As a guess I would say human activity has added to more than 1/2 the increase.
So if you removed humans from it, what causes CO2 levels to lower when it's gets cooler and what causes increasing CO2 levels when it gets warmer- I'm not sure we understand this enough at this time and until such time it's hard to know how much humans are adding.

But even with the idea that human are adding all of the increase, I don't think the rather insignificant increase in global CO2, is much of a factor in increasing global temperatures.
In other words, if we were start a serious cooling trend- I don't think a program of adding significant levels of CO2 and/or Methane to our atmosphere would reverse the cooling trend.