The Roman Empire and the Chinese Han Dynasty were responsible for significant greenhouse gas emissions, according to a study which contradicts UN scientists’ view that man-made climate change only began with the Industrial Revolution.
Core samples from Greenland’s ice, which faithfully record the planet’s atmospheric conditions, showed that methane levels significantly rose about 2,000 years ago and remained constant for around 200 years, coinciding with the height of the 2 great empires.
Lead author of the study Celia Sapart of Utrecht University told Reuters, “Per capita they were already emitting quite a lot in the Roman Empire and Han Dynasty,” and said that methane was probably released during deforestation to clear land for farming and from the use of charcoal as fuel, for instance to smelt metal to make weapons.
The study, published in the journal Nature, found that rates of deforestation “show a decrease around AD 200, which is related to drastic population declines in China and Europe following the fall of the Han Dynasty and the decline of the Roman Empire.”
The world’s population 2,000 years ago was around 300 million and their contribution to global emissions were significant, but still tiny compared with the emissions of the 7 billion on Earth today. Sapart estimated that methane emissions until 1800 were about 10% of the total for the past 2,000 years, with 90% occurring since the Industrial Revolution and the great surge in the use of fossil fuels. She said, “The pre-industrial time was not a natural time for the climate – it was already influenced by human activity. When we do future climate predictions we have to think about what is natural and what did we add. We have to define what is really natural.”
The study noted a second rise in methane in the Medieval period, which coincided with a warm period from 800 to 1200 AD, the emergence of Europe’s economy from the Dark Ages, and population growth in Asia and Europe which led to more deforestation for farming. It fell back again when the Black Death ravaged Asian and European populations. A third rise in methane levels occurred around the start of the ‘Little Ice Age’ in the 1500s, as populations recovered after the plague.