Many people don’t realize the impressive scientific and engineering know-how of various ancient cultures, be it the Chinese or the Greeks. In particular, the Greeks and later the Romans had figured out a many things correctly about the world. By the 3rd century BCE not only did they know the Earth was round, but they knew the size to about 15% accuracy of the value we know today. Various internal organs had their basic function understood, including the kidneys and with that the renal system. Nerves were also uncovered, and the differences between motor and sensory nerves could be determined by sight.
Technologically, there are things that still blow me away. The Romans had figured out concrete, including a version that could set underwater, a material used in some of the impressive structures of that era, including the Colosseum. Reasonably accurate water clocks were in use which were superior to the sundials. We also have examples of mechanical computers from the 1st century BCE (the Antikythera mechanism). There was also a considerable manufacturing base across the Roman Empire.
And that is beginning to become more and more pronounced in the ice and geological records. A recent study in Nature shows a peak in methane (a powerful greenhouse gas) in the atmosphere at around the peak of the Empire (c. 200 CE). (Some discussion here and here.) Why the methane release? The Romans had a lot of metal production; to get iron well-smelted, you need a strong fire, and charcoal was burned in great quantities. The same with copper mining and production. And it shows!
In addition to the Romans, the Han dynasty in China was booming up until about the same time the Roman Empire had peaked.
The results of such pollution had already been known from ice core samples from Greenland showing heavy metals in greater abundance than any time up to the Industrial Revolution! One could only imagine what the climate would be like today if the Roman and Had power structures held up. Would the world be like it was in the episode of Star Trek, a 1960s version of Rome and its emperors, and even hotter than today and more polluted? Perhaps the Romans and Chinese would have advanced and realized their effects on the environment and we would have already had the global warming debate. Obviously speculative, but that is what happens when great civilizations fall.
(If you are interested in why the Roman Empire fell, that has had centuries of argument, but it seems most likely due to the unstable political system it had, especially in how a new ruler was to come to power. And you can blame Caesar for that in part. See Adrian Goldsworthy’s How Rome Fell.)
What is the importance for such a study? A key reason seems to be to better calibrate climate models which have tried to take periods before the Industrial Revolution as a baseline for how nature tends to change back and forth. But if there was significant greenhouse gas production by humans in the past 2000 years, that can upset those calibrations a bit. Thus, learning about the past will improve our climate models so we can better predict the future. And along the way we discover just how industrious past cultures were. I don’t know how much this new data will tweak climate models (which now cover periods of hundreds of thousands of years or more into the past), but fine-tuning is the bread-and-butter of good science. We’ll have to see if there are any new conclusions, but I don’t foresee any revolutionary reversals on the nature of global warming.
Oh, and on the subject of global warming, look at that crazy-huge peak in methane in the last century. That ain’t natural!