The Mycenaeans of Ancient Greece

Three thousand years ago, the Mycenaean civilization thrived along the Aegean Sea. The Mycenaeans grew wheat, barley, figs, and produced olive oil and wine. They also raised bees, oxen and sheep. They were a seafaring people and prospered through trade. They exported hides, wool, timber, wine and olive oil in exchange for tin, copper, ivory and linen. Their artisans included bronze smiths, potters, goldsmiths, weavers, shipwrights and perfume makers. The royal house of this empire was in the city of Mycenae, 60 miles southwest of where Athens, Greece, is today. The gate of the palace wall was guarded by huge lions carved in stone. They were so massive that legend attributed the work to giants.

The decline and fall of Mycenae was so sudden and so complete that its ruins lay undiscovered for thousands of years, until the 1870's when it was rediscovered by archaeologists. Until then, this fabled civilization survived only as a vague memory, recorded for posterity by two literary classics, The Iliad and The Odyssey. These stories were written by the Greek poet, Homer, 600 years after Mycenae vanished. The decline of this civilization was marked by violence as palaces and granaries were burned. The question is why?

A devastating drought appears to have immediately preceded the collapse of Mycenae. Today, January rains are essential for Aegean farmers to grow crops. In most years, the jet stream's winter storm track reliably brings the much needed rain. In 1955, however, the jet stream shifted 100 miles to the north, causing a severe drought. In contrast, Hungary, through which the jet stream now passed, experienced unusually heavy rainfall. Scientists suggest that a similar, but longer sustained shift in the jet stream took place about 1200 BC. Written records of the Hittites tell of famine near this time. The Hittites controlled the land where Turkey is today and would be affected similarly to Mycenae with a change in the winter storm track. In addition, the New Kingdom of Egypt was also coming apart as they suffered from the effects of a drought and around 1200 BC the Hungarian civilization was disrupted by flooding. (Remember the rain has to go somewhere!)

If you remember from an earlier post, the time between 1200 and 1100 BC is considered to be a time of general crisis in the “known” world. Within a century, states large and small along the Mediterranean coast from Anatolia to the Delta and from the Aegean Sea in the west to the Zagros Mountains between Iran and Iraq in the east collapsed or were destroyed. The average global temperature had dropped around 4 degrees about this time and this undoubtedly disturbed the flow of air around the globe and changed the boundaries between the cold Arctic air and the warm equatorial air.

Next Post: More about the Jet Streams

How Does Weather Work?

First, the earth is rotating (You knew that, right?)

Second, warm molecules move away from each other faster than cooler molecules. This means that warm air rises – the force of gravity is less on warm air because it is less dense than cold air. As it rises it creates an area of low air pressure - there are fewer molecules in a given volume of warm air that cold air. However, as it rises, it also cools and that means it can hold less water vapor. The water vapor turns back into liquid water and….it rains! The heat that is lost as water vapor returns to its liquid state can precipitate thunder storms and sometimes tornadoes and hurricanes.

Third, cold air sinks. Sinking air makes an area of high pressure - more molecules in a given volume of air. In general, air from an area of high pressure flows towards an area of low air pressure. The movement of air from an area of high pressure to an area of low pressure is what we call wind. The greater the difference in pressure is, the stronger the wind.

The greatest pressure difference on the earth is where the warm equatorial air hits the cold polar air. The cold air pushes under the warm air. The rising air that results from the clash of the cold air from the poles and warmer air originating from the equator produces a narrow band of strong winds that blow 20,000- 40,000 feet in the upper atmosphere. These upper atmosphere winds circle the Earth's north and south poles at speeds of 80-190 mile an hour. These ribbons of fast moving air are called the Jet Streams.

Because of the rotation of the earth, the general flow of jet stream in the Northern Hemisphere is from the west to the east. But it often dips southward or rises northward as it flows around the earth. During the summer in North America, the jet steam is located around the Canadian/US border and is relatively weak (the temperature difference between the polar and equatorial air is not as great). In the winter when the temperature difference between the polar and equatorial air is greatest, the jet stream picks up in strength and dips down into the United States.

Because the most violent and variable weather is produced when cold air clashes with warm air, storms occur frequently along the path of both the Northern and Southern Hemisphere jet streams. The major agricultural lands of the world are located under the storm path of the jet streams. It is where many of the world's first civilizations began and is where we grow most of our crops today.

What do you suppose happens when overall global temperatures rise or fall? The path of the jets streams change, therefore where it rains also changes and that means our ability to grow food will change. Not enough rain, there will be droughts. Too much rain and there will be flooding and even more importantly, as we will see later, there will be an increase in plant disease. Either way, crops don’t grow and produce well and there will be less food to go around. If the climate change lasts for a long period of time, it can disrupt rain patterns enough to bring down a civilization.

It is the long term availability of food that makes or breaks a civilization!

Next Post: The Mycenaeans of Ancient Greece
How Global Warming Works

The Sun

Because of the relative sizes of the earth and its sun (the sun being much bigger), the rays of the sun travel in parallel lines to the earth and through the earth's atmosphere. Only about half of the incoming rays get to the earth's surface because air molecules, clouds, and dust either absorb some of the rays or reflect them back into space. The sun's rays that do penetrate the earth's atmosphere warm the earth's surface but despite the fact that they all begin with the same potential energy, the incoming rays have different heating effects at different places on the earth.

The Rays of the Sun as They Travel Through the Earth’s Atmosphere at the Equator and at the North Pole (Winter in the Northern Hemisphere – Summer in the Southern Hemisphere)


If you look at figure above, you will see one of the reasons why. Because of the curvature of the earth, the sun's rays travel through more atmosphere and therefore through more air molecules and dust to reach the poles than they do at the equator. (And it hits a bigger area at the poles.) So although the energy coming from the sun is the same, less of the sun's energy reaches the poles than the Equator. In addition, the snow and ice at the poles reflects much of the sunlight back into the atmosphere.

Consequently, the Earth is most intensely heated by the sun at the equator and least at the poles. The exact same phenomenon of uneven heating occurs in the oceans as well. The oceans at the equator are warmer than that closer to the poles.

Once the land and oceans of the earth absorb the sun’s rays, the energy is transferred into heat and this heat is then reradiated back out into the atmosphere. Much of that heat is absorbed by the molecules in the air (such as carbon dioxide). Since there is less energy reaching the poles there is less heat radiating from at the poles and the air is cold. Conversely, the intense energy reaching the equator means that the air at the equator is hotter.

In addition, the energy from the sun is also used in the process of evaporation (water changing from a liquid to a gas). The hotter the air, the more evaporation can occur. Warm air evaporates more water than cold air and it can hold more water molecules in the form of vapor than cool air. Consequently not only is the air at the equator warmer it is also “wetter”.

These differences in the heat and water vapor in the air prime the global weather machine because weather is really nothing more than an attempt of air molecules to homogenize these differences.

Next Post: How Does Weather Work?
How Weather Works

It is all Temperature Differentials!

Although the sciences of Meteorology (the study of the weather) and Climatology (the study of climate) can be very involved, there are some basic concepts we all can understand about the factors that contribute to the weather and global climate. Basically the weather and climate of our earth is shaped by four things:

1. The Sun, the variation in the amount of incoming solar radiation reaching the earth and the amount of heat that escapes back into space.

2. The Earth, its tilt, its rotation, and the distribution of its continents and its oceans.

3. The Air, its movement vertically in the atmosphere and horizontally around the globe.

4. And Water, its behavior in the air and in the currents of the oceans.

The most important of these is the sun for it is the interaction of the sun with the other three that drives the earth's weather and defines the global climate of our earth.

Question to answer: What is the difference between weather and climate?

Next Post : The Sun

The Americas

China was not the only civilization to rise during the “Crisis of the Known World”. While the three civilizations of the Near East were collapsing, the first complex societies were also arising in Mesoamerica (the Olmecs) and South America (the Chavín). By 2000 BC people began to settle permanently in river basins draining the western slopes of the Peruvian Andes and the Tuxtla Mountains in Mesoamerica. By 1000 BC, the Chavín of Peru and the Olmecs of Mesoamerica had built massive ceremonial centers and their warriors were spreading their influence through their respective territories.

The Second Group of “First” Civilizations (Note again – along rivers!)

But then in 900 BC the Chavín were ravaged by floods and starvation and there was revolt among the Olmecs. By 200 BC the civilizations of the Chavin and the Olmec were just a memory.

Like before, but in reverse, while China was racked by constant warfare and the first civilizations of the Americas were dissolving, in the Mediterranean, civilizations were growing --- again. This time Greece and Rome were on the rise.

Again look at the climate graph in the second post. What was happening with the global temperature? It was rising back up to where it was when agriculture was first invented and the very first civilizations arose. With the increase in global temperature civilization in the Mediterranean gets back on its feet only to crash again. The decline of the Western Roman Empire happened between 200 and 600 AD.

Notice, the global temperature fell again. Interesting! What is going on??

To understand what was going on you need to have some understanding of how weather and climate work on our Earth.

Next Post: It’s all Temperature Differentials!
“Science Content”: Atmospheric Science

Interestingly, while the first civilizations in the Middle East and India were collapsing, civilization in China and in the Americas was rising.

China and the Yellow River

As the climate warmed from 5000 BC to 3000 BC, more and more people began to settle in farming villages along the river banks of the Yangtze River in South China and along the Yellow River in Northern China just as they had done along the rivers of East Asia. This time period is called the pre-dynastic period of China. During the pre-dynastic period, villages grew larger and more socially organized. Pottery became more elegant, burial customs became more elaborate, and distinct social classes began to emerge. Clan leaders began to surround themselves with assistants and advisers, the beginnings of a bureaucracy. Then somewhere around 2200 BC, the Yellow River flooded thirteen years in a row and something had to be done. (Remember - 2200 BC is when drier weather became more and more of a problem in Sumeria and Egypt! Guess where the rain was going!)

According to Chinese legend a man known as “Yu the Great” solve the flooding problem by organizing the people of North China and building a vast system of dikes and channels. He was so successful that he was eventually made the first king of the first Dynasty of China, the Xia Dynasty (2000-1600 BC). This Dynasty was followed by the Shang Dynasty (1600-1100 BC) and the Zhou Dynasty (1100-770 BC). Chinese civilization was on the rise.

But then, during the period between 770 and 256 BC, all began to fall apart. This was a time of “political fragmentation and moral crisis” in northern China.

A king and his dynasty could rule only so long as they retained heaven’s favor. If a king neglected his sacred duties and acted tyrannically, heaven would display its displeasure by sending down ominous portents and natural disasters. If the king failed to heed such warnings, heaven would withdraw its mandate, disorder would increase, the political and social order would fall into chaos, and heaven would eventually select someone else upon whom to bestow a new mandate to rule. Patricia B. Ebrey

It was not the King’s fault. The global climate changed again.

Next Post: The Americas

Today we live in a world powered by oil and gas. We can put our cities just about anywhere. Food is shipped in and most of us in developed countries do not know where our food comes from – or if we do - we do not think about it much. However we all need to start thinking about it. To understand how important it is, it helps to take a quick look at a few of those early civilizations that have left us only monuments….

Three of the World’s First Civilizations (Did you notice they were all along rivers?)

The First Civilizations

Between 6000-3750 BC, a major cultural change in human behavior was again taking shape. People of unknown origin, which we call the Sumerians, moved out the mountains and began to settle in the southern flood plain of the Tigris-Euphrates Valley. Little is known about these people but it is certain that over the course of 2000 years the Sumerians learned to manage crops and animals in the heat and aridity of the lowlands of Mesopotamia. The key to their success was irrigation. In addition, the most important inventions of humankind, the plow and the wheel, came into use. With increasing skill and organization, these irrigation farmers harnessed the destructive spring floods of the Euphrates River, improved their crop yields to the point of producing surpluses, and laid the foundations of the world's first civilization, the city-states of Sumer.


Not long after the beginnings of Sumerian civilization, the elements of civilization emerged along the banks of the Nile River in Egypt and the Indus River in modern day Pakistan. Two civilizations also flourished in the Mediterranean, the Minoan and Mycenaean. Each of these civilizations had their ups and downs. Each made major contributions to human kind but what ties them together is the timing of their final demise. Starting around 2200 BC and culminating around 1200 BC….

“… states large and small along the Mediterranean coast from Anatolia (Turkey) to the Delta (of Egypt) and from the Aegean Sea in the west to the Zargos Mountains in the east collapsed or were destroyed in what seems to have been a general crisis of the civilized world.” Civilization in the West

Look back at the global temperature graph in the previous post. Notice something? The global temperature around 1200 BC was at its lowest point in 3000 years and had been decreasing for about 1000 years. Though historians can and do argue about the cause or causes of each states demise, every one of these civilizations had at least two important things in common – dependence on agriculture and drought.

Drought is lack of rainfall. Growing crops and growing populations require rain either directly or flowing into rivers to use for irrigation. Once human populations became dependent on agriculture to feed themselves, they make themselves dependent on the global climate. Hunter/gathers can move to where the rain is falling, city dwellers can not. When their agriculture is threatened there will be major disruptions in the organization of civilizations created when the climate was right for agriculture. It is just that simple!

The period of time between 1200 and 800 BC is known as the “Greek Dark Age,” at time when the people of the time returned to a “more primitive level of culture and society”.

Next Post: China and the Yellow River
Why Eurasia First? It’s Geography!

Civilization Began, Civilization Crashed
Either Way the Climate Changed!

If you read the Jarad Diamond’s article, “Agriculture, the Worst Mistake in the History of the Human Race”, you know that he gave several reasons why moving from a hunter/gatherer life style to farming was a big mistake. The article is full of thoughts that rattled my brain when I first read it. I too had always considered agriculture as a good thing. My grandfather and my father were farmers after all. However the more I thought about it, the more I realized that he was right. However it is too late now. We are dependent on agriculture and one of the most important reasons we need to be fully aware of that is the second reason he gave…

“…because of a limited number of crops, farmers ran the risk of starvation if one crop failed.”

We can deal with the “limited number of crops” later. Right now I want to deal with “if one crop failed”.

Why do crops fail????? The weather – if it is too cold, crops freeze. If it’s too hot and dry, crops wither and die. If it is too wet … well that is more complicated. The thing to understand is that weather in any individual place where crops are grown, whether it is too wet, too dry, too cold or just right for agriculture, depends on the global climate.

Take a good look at the graph below. What do you see?

First, you should see the rising and falling of the global temperature over the last 8000 years. Second, you should see that the differences are relatively small, only 1-2 degrees. Third, there are two major civilization crashes located on this graph. The first depicts the time the world’s first civilizations declined and the second is the fall of the Roman Empire. Note that both declines coincided with a decrease in global temperature. And then there is the Little Ice Age...

Next Post: The First Civilizations

Climate Change - Patterns in Time
The Biology of Human Civilizations and the Climate

I am starting this blog first and foremost because I am fed up with the “climate change deniers”. But really it is more than that. It is also because I believe that even the people who know and understand the seriousness of the global climate change (that is happening now) are missing one very important reason for controlling our carbon dioxide output. It is more than the predicted increase in the severity of storms or a rise in sea level (and that is bad enough!). It is the very survival of our present day civilization that is in peril.

I am a plant pathologist and at the end of the last century I had the privilege of working with one of my graduate advisors on the development of college class to teach biology to undergraduates in the hopes of luring some of them into the field of Plant Pathology. I eventually ended up teaching the class online for several years and wrote a book specifically for that online class. In the process of writing that book, I learned just how important the world’s climate has been for past human civilizations.

Like many others, I have always had a fascination about past civilizations like the Maya, the Minoans, and the Moche, to name a few. What had happened to these once great civilizations? As I was doing the research required for this new biology class, taught from the point of view of a Plant Pathologist, I found a new insight into what must have happened to these civilizations.

It is this insight I would like to share with any who will find and read this blog. So here goes…..

Introduction

To understand why global warming today is so important we have to go back about 10,000 years to another time of global warming.

Like human beings all over the globe 10,000 years ago, people in a place called the Levant were living in mountain caves and making their living by hunting and gathering. They fed themselves by fishing, hunting gazelle and other mammals, and by gathering fruits, roots, and seeds including the intensive gathering of many wild cereal grasses. Then, between 13,000 and 9000 BCE, their world began to change. The global climate was warming and these people began to settle in villages and build houses of stones and mud bricks. By 7000 BC these people were evolving into the world's first farmers. From that time on, most human beings have been feed by agriculture not by hunting and gathering.

This is important for several reasons. First, agriculture can support higher population densities than hunting and gathering. Second, the transition to agricultural set the stage for the next step in the story of human evolution – the development of what we call civilization. There are many definitions of civilization but basically civilization means the presence of densely populated cities/states, and the bureaucracy to run them.

The very first civilization, or state society, evolved just east of the Levant in the river valley of the Tigris and Euphrates Rivers south of the Zagros Mountains. (You know… IRAQ!) Over the next 2000 years, agriculture spread from the Levant. It spread eastward down the river valleys of the Tigris and Euphrates of today’s Iraq and to the Indus Valley in Pakistan. It spread south to the Nile Valley of Egypt. It spread north into Turkey and Southern Europe and into Greece. Civilizations all across the Middle East flourished.

However, somewhere between 2000 and 1200 BCE, these civilizations descended into chaos. They left us with grand monuments (Sumer, Egypt, Minoan) and a great mystery to ponder…What happened?

Guess what…. the global climate changed!

Except for the global warming that happened 10,000 years ago, the climate changes of the last 8000 years have been times of global cooling, not warming. However, what you need to know is this. For modern humans, it does not much matter whether the global temperature is going up or going down.

What matters is that it is changing!

Why? It’s because both global warming and global cooling change where it rains and we humans put our civilizations where it rains.

And why is that? Simple put, it is because we build our civilizations where people can be fed. And guess what - the plants we eat and the plants we feed to the animals we eat need water to grow!!!!! And just enough water, not too much and not too little! Putting it another way…..

It’s Agriculture!!!!

Next post: : Civilization Began, Civilization CrashedEither Way, the Global Climate Changed!

Something to read and ponder before the next post.