Some critical thought is needed here. The mean global temperature rise attributed to humans since the industrial revolution is approximately 1 degree Celsius. Divide the C02 output of campfires by sparsely populated prehistorics by the CO2 output since the industrial revolution, multiply by 1 degree Celsius, and then ask how such an infinitesimal change could be detected against a backdrop of ice ages in the presence of forest fires and other natural sources of CO2.
Just for the record Brian the human sourced CO2 input was not just from camp fires but the widespread practice of deforestation through burning the entire forest down.
We do see the record of these occurrences in the fossil record pretty clearly, like when humans arrived in Australian starting about 50,000 y/o. The record is not only in sources that describe atmospheric chemistry but ash layers and individual fossils within subsurface strata.
Second, we see a shift in CO2 associated with human behavior that corresponds with multiple transitional periods of human conduct, one when the use of fire for hunting (driving herds on the savanna, or burning forests) shifts to even larger scale burning to push back jungle, forest and savanna for agriculture (we don't call it slash and burn for nothing) and then again as we enter the Bronze and the first large scale urban populaces of the post neolithic period.
BTW I said we could measure the impact, not that these practices were resulting directly in Global Warming. I suggest you take a little more time to review the extensive work on paleo-climatology that is being laid out with a combination of tree ring and fossil geological data to corroborate the impact of human behavior on climate. While it certainly is complex it is being done. The models clearly have a high degree of error but paleontology depends very closely on geological data and the ability to map when we see volcanic aerosols and gases, as opposed to other sources is relatively clear.
IOW we can tell from the records being formed when it is nature by itself and what are the various sources and when something else is being added to the mix. We can then correlate that data with other records to look for alternative sources and sometimes we do find them but more often than not we are seeing the alternative is some form of human behavior that has fossil evidence associated with it.
Some clear examples for human input during the bronze age are as simple as chemical signatures from smelting others like in the case of Australia are more complex but are demonstrated in the fossil record by the extent of the widespread destruction of habitat for many life forms, the spike up in extinctions that is associated with the introduction and subsequent spike up of human population that correspond to atmospheric chemistry of the period and measurable global mean temperature shift.
We can see the forests and prairies burning in the soil layers and also see the rate of these occurrences is not always associated with naturally occurring droughts, volcanoes etc but with the introduction of these practices by humans.
This is not hyperbole, or bad science, it is complex and it does integrate homogeneous data from a large number of heterogeneous sources so in that respect you have a point.
However you have made a mistake if you are thinking I suggested that all global warming during this period is due to human activity. I have never claimed anything like that, I said we can measure the impact of human behavior a remarkable way back and I also said the degree of error increases the farther from the present we go.
However we do not have one single homogeneous source, we have
multiple homogeneous sources of information and their data can be cross referenced to produce a remarkably accurate detailed analysis of climate (and some human conduct) extending back millions of years. So long before the human presence that despite the controversy about the extent of the human impact, the evidence of that impact is as clear as a footprint in stone.
The data I refer to are a combination of ice cores, ocean sediment cores, tree rings, fossil diatoms, pollen and insects that all demonstrate high sensitivity to temperature, physical evidence of human behavior from digs, geological strata that all contribute chemical, temperature and atmospheric humidity info to the mix and can be cross correlated by alignment with specific key events of a global nature like super volcanic eruptions etc.
No it is not perfect and it does depend to a great degree on a modern forensic analysis, not just geology anymore but it is remarkably consistent in its message from independently sourced data from around the world.
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