As I read into Fingerprints of the Gods by Graham Hancock and learn more about antiquity, it becomes clear that weather conditions on Earth were far more hostile then (say, 15,000 years ago) than now. Looking way, way back into millions of years ago, scientists have plotted global average temperature and atmospheric carbon, mostly using ice cores as I understand it, yielding this graph:
I’ve seen this graph before, which is often used by climate change deniers to show a lack of correlation between carbon and temperature. That’s not what concerns me. Instead, the amazing thing is how temperature careens up and down quickly (in geological time) between two limits, 12°C and 22°C, and forms steady states known at Ice Age Earth and Hot House Earth. According to the graph, we’re close to the lower limit. It’s worth noting that because of the extremely long timescale, the graph is considerably smoothed.
Another graph showing the last 20,000 years (much more relevant to human history) reveals some wild fluctuations before settling into a roughly 10,000-year nested steady state sometimes called Garden Earth:
Here’s another graph showing the climate coming out of the last glacial period into Garden Earth:
Different ways of framing the data (e.g., varying time scales and starting points) suggest different conclusions, which is both understandable yet questionable when one is pushing an agenda. It’s a way of lying with numbers. A further graph, somewhat entertaining, is found at this link. It represents scale much better than most but unaccountably lacks the wild fluctuations between 10 and 20 thousand years ago shown in graphs 2 and 3 above. What it does show is the sudden temperature rise in the era of industrial civilization along with three projections toward the year 2100.
My observations are two: (1) a much wider range of climate (using global average temperature as a proxy) is demonstrated in history over the relative calm of the last 10,000 years, and (2) if human contributions to climate change are currently in the process of ejecting us from Garden Earth (echoing expulsion from the Garden of Eden), the turbulence we can expect is cataclysmic. Indeed, that’s what Hancock describes during the period before settling into Garden Earth. Though catastrophic episodes were probably separated by many generations, the Earth was a literal slaughterhouse, with animals (including humans) dying en masse, some species of megafauna going extinct in the process. Bone breccias (a/k/a osseous breccia), some found high in the mountains, suggest flight from flood, fire, flash freeze, or storm before eventually succumbing.
As with global average temperature swinging like a pendulum over millions of years between 12°C and 22°C limits, drivers of climate change occurring in short periods of time (tens of thousands of years) are unclear. Candidates include asteroid impacts, solar activity, periods of high volcanic and earthquake activity, and subtle changes in atmospheric and/or oceanic chemistry that trigger phase changes (think of a pot of water that remains calm until it reaches boiling point and roils to evaporation, or toward the other end of the spectrum, freezes solid as ice). It’s also a good question whether climate drives major disruptions in the Earth’s crust or the other way around. However, one factor that never existed before is anthropogenic climate change.