Climate Variations During the Holocene Interglacial

Climate change activists depend on the ignorance of people. The less someone knows about climate and climate history the easier it is to coax him into accepting their claims.

In the last part of The Climate Change Myth, I described the Eemian Interglacial, the last interglacial before our own. Now let’s have a look at the climate history of our own interglacial, the Holocene.

Just like an ice age with its alternating cold and less cold intervals an interglacial has warm and less warm stages. This is true for the Eemian as it is true for the Holocene.

The Holocene is the seventh interglacial in our current ice age, the Quaternary. As described in Ice Age 5 we live in Earth’s fifth ice age. It’s still young – only about 2.58 million years old. The preceding four ice ages differed in length between 30 million and 300 million years.

Thus, we are living in the seventh interglacial of the fifth ice age. It’s only a tiny sliver of time, this seventh interglacial, measured against the 4.5 billion years of Earth’s existence. And without the warm climate of our Holocene interglacial there would be no history of human civilization to look back upon.

The Holocene began around 12,000 years ago following one hundred thousand years of glaciation called the Wisconsin glaciation. It is no coincidence that you live your life during this interglacial. Without it chances are you would not live at all. The benign weather conditions of the Holocene interglacial made it possible for humans to multiply, to thrive and to be creative. Civilization followed in the wake of warm weather conditions. The history of mankind would have been very different if the Wisconsin glaciation had continued until today.

The seven interglacials during our current ice age have been shorter than the periods of glaciation. The Eemian, for example, lasted about 16,000 years. The glaciation period between the Eemian and the Holocene was 100,000 years long. The Holocene began around 12,000 years ago.

It is not unreasonable to assume that our interglacial will be followed by an area of glaciation – as has happened after every single one of the six preceding interglacials during our current ice age. When this will happen – who knows?

We owe our civilization to the mild weather conditions of the Holocene. Nonetheless, the climate even during our temperate interglacial has not been steady. It hasn’t been wildly fluctuating and unstable as is typical for the climate during periods of glaciation. Its variations have been more moderate. Even so the consequences of those temperature variations on life on Earth and in particular on human civilization have been significant.

If we start our climate survey of the Holocene during the time of the Romans and continue it to the present day, we discover various well-defined and distinct climate intervals:

  • The Roman Warming (250 BC—450 AD)
  • The Dark Ages (535–900 AD)
  • The Medieval Warming (900–1300 AD)
  • The Little Ice Age (1280–1850 AD)
  • The Late 20th Century Warming (1850 AD to the present)

During both the Roman Warming and the Medieval Warming, global temperatures were higher than today. During the Dark Ages and the Little Ice Age, temperatures were lower than today.

During the Late 20th Century Warming, the Earth began to recover from the long “Little Ice Age” – which really wasn’t an ice age at all but a less warm period during the current interglacial.

Let’s have a closer look here at one of these epochs – the Roman Warming. Geology professor Ian Plimer describes this period at length in his book “Heaven and Earth.”

The Roman Warming lasted for roughly 700 years, from 250 BC to 450 AD. It overlaps with the expansion of the Roman Republic and later the Roman Empire into a vast realm encompassing much of Europe, North Africa and the Near East. Plimer writes that “grapes were grown in Rome in 150 BC. By the 1st Century BC, Roman scribes record little snow and ice and that vineyards and olive groves extended northwards in Italy. At the peak of the Roman warming, olive trees grew in the Rhine Valley of Germany. The location of vineyards is a good climate proxy. Citrus trees and grapes were grown in England as far north as Hadrian’s Wall and most of Europe enjoyed a Mediterranean climate. This suggests a very rapid warming. It was also wetter. Temperatures in the Roman Warming were 2 to 6ºC warmer than today.”

There was plenty of food to feed the increasing population. Egypt was of strategic interest to Julius Caesar since it produced grain in sufficient amounts: “Because of regular and higher rainfall, North Africa became a breadbasket for the Carthaginians and later the Romans. It is now mostly desert.”

This warming was global and not restricted to Europe and North Africa: “Central America was wetter than now and Central Asia responded to the warmer wetter times with a strong population increase around 300 AD. Pollen studies show that vegetation thrived. It was also warmer in Antarctica in Roman times. Skin and hair from mummified elephant seals preserved on Holocene raised beaches in Antarctica tell a story. Mummified seals dating from the Roman Warming and Medieval Warming were found well south of the modern breeding and molting grounds.”

The living standard of people increased. They were better fed, healthier, better educated and more prosperous. Roman technical ingenuity led to amenities like running water and street lighting, vast networks of roads, aqueducts and bridges: “The good weather during the Roman Warming meant that crop failures and famine became a rarity. There was an excess of food, population increased and the great Roman construction projects were undertaken using the excess labor and wealth. England had at least 5.5 million people, all of whom could be fed. It was not until the Medieval Warming (900 to 1280 AD) and the late 16th Century that England again had a population exceeding 5.5 million.”

What about the CO2 content of the atmosphere during the Roman Warming? It is known that during the last period of glaciation the CO2 content was much lower than today at about 190 ppmv. At the beginning of the Holocene CO2 had risen to approximately 250 ppmv. In the last 8000 years the CO2 content of the atmosphere has increased to 391 ppmv today. Although global temperatures during the Roman Warming were higher than today, the CO2 content of the air was lower. These facts alone disprove the claim of anthropogenic global warming advocates that CO2 is the main climate driver.

Patrick Moore, one of the founders of Greenpeace, describes CO2 as “the currency of life.” Without CO2 there is no life. It’s an essential trace gas in our atmosphere and we depend on it for our survival. It does not drive climate but tends to follow increases in temperature by several hundred years.

Part 4 “The Little Ice Age” will follow.